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2. Practical Attainment of Traceability

1. Normally the material most closely R8 resembling the material under test will be analysed 5 INSTRUMENT OPERATING CONDITIONS The temperature control of the muffle furnace is set via the Eurotherm controller on the instrument Full operating instructions may be found in the manual but the following VIII LGC VAM Traceability Guide 7 2 7 2 2 7 2 3 7 2 6 LGC VAM Traceability Guide parameters must be set CHARRING Dwell 1 CED 30 minutes Level2 2 500 C ASHING Dwell 2 d2 960 minutes Total duration of programme is approximately ENTE SAMPLE PREPARATION The sample must be comminuted as finely as possible mixer chopper mincer etc and then homogenised in a food processor or liquidiser Care must be taken not to contaminate the sample only stainless steel or plastic implements should be used where possible METHODS OF ANALYSIS 7 1 Dish cleaning procedure Silica dishes 2 2 must be cleaned before each analysis as follows Soak the silica dishes 2 2 at least in 10 nitric acid 3 6 in a plastic container This container must be stored in the fume cupboard Rinse the soaked silica dishes copiously with purified water If the dish contains any particle residues clean it with a plastic brush and rinse with purified water Place the dish on the hot plate heated to 8 to dry then cool to in a desiccator until required for use Ashing Procedure 7 2 1 We
2. Note See SOP INS I for details on the derivations for Cs and 7 5 Acceptability Criteria for QC material results The results obtained for the QC material must lie within the acceptable in house limits If the results falls outside the action limits fail the associated batch and repeat the samples Inform the responsible analyst and record the failure in the trace element QC failure action book trace element laboratory together with the corrective action taken to remedy the situation G2 A7 A7 G4 G4 G2 AS G4 G2 A5 R10 R10 AS A4 LGC VAM Traceability Guide 7 2 SOP INS 1 QUANTITATIVE ANALYSIS OF AQUEOUS y 4 EXTRACTS BY INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY SCOPE The method is applicable to the quantitative determination of elements in the mass range 7 to 260 amu in diluted and undiluted aqueous extracts at concentrations in the range 0 01 ng mL to 0 5 g mL The method is not applicable to the determination of organometallic compounds such as alkyl lead or mercury compounds PRINCIPLE The sample extract is aspirated into the plasma of the ICP MS instrument and the positive elemental ions that are produced are passed into a quadrupole mass spectrometer where they are separated according to their mass charge ratio The ions are detected by an electron multiplier tube and are quantified by comparison to a previously prepared calibration curve for the isotopes elements
3. Add of 50 hydrochloric acid 3 3 using a tilt measure 2 3 and carefully transfer the dishes to a hot plate in a fume cupboard Evaporate to dryness but do not bake the sample Add a further of 50 hydrochloric acid 3 3 warm the dish for approximately mm and then transfer the solution with the aid of a funnel to a plastic using distilled water for washing Care should be taken not to allow the solution to run down the outside of the dish Add a further of 50 hydrochloric acid warm the dish for approximately then transfer the solution to the same flask Rinse the dish with purified water into the flask Allow the solutions to cool to room temperature and then mixing well On standing if a solution contains particles filter through an ashless filter paper and treat blank s and reference material s similarly Store the solution in a plastic bottle previously rinsed with 596 nitric acid 3 5 and distilled water Measure the trace element concentration by inductively coupled plasma emission spectrometry SOP INS 1 7 4 Calculation of Results In put the results measured by ICP MS into the following equation applicable for the following elements Na K Ca Mg P Cu Fe Mn and Zn C C V Concentration of element mg 100g CELA 10x W Where Cs Concentration of element in sample solution ug mL as determined by ICP MS Concentration of element in sample blank solution ug mL as determined by ICP
4. into a Stock Solution Aliquot mL Fluoride Chloride Nitrate Phosphate Sulphate 5 4 Calibration Solutions Using glass pipettes dilute aliquots of the mixed stock solution 45 5 3 to respectively in volumetric flasks 5 5 Compound to be used to prepare stock solution Concentration in the mixed stock solution mg litre Quantity g of compound to be dissolved in 1 litre of 5 R6 A4 R6 A4 R6 A4 R6 A4 R6 A4 A5 A5 A5 A5 A5 A5 The three diluted mixed solutions and the undiluted mixed solution 5 3 provide four calibration solutions as tabulated below Calib Std 4 mg L Fluoride 4 Chloride 60 Nitrate 50 Phosphate 5 Sulphate 75 XXIV Calib Std 3 mg L 2 4 36 30 3 45 Calib Std 2 mg L 0 8 12 10 1 15 Calib Std 1 mg L 0 1 1 5 1 25 0 125 1 875 LGC VAM Traceability Guide 6 1 6 QUALITY CONTROL MATERIALS Two types of QC material may be used A solution is prepared in house by diluting 25 mL of an imeem ou OVE Brei 5 2 to 100 mL A certified reference material e g BCR 616 Ground water 7 ION CHROMATOGRAPHY Set up the equipment according to the manufacturer s instructions Ensure there is sufficient eluent in the reservoir and set the pump at the appropriate flow rate Once the system has stabilised after about DENM check that the background conductivity of the eluent is
5. Meeting the Traceability requirements of 15017025 An Analyst s Guide Third Edition September 2005 CEA VII valid analytical measuremen IN The work described in this guide was supported under contract with the Department of Trade and Industry as part of the National Measurement System s Valid Analytical Measurement VAM Programme ISBN 0 948926 23 6 Published by LGC Limited Subject to Crown licence no part of this publication may be reproduced or transmitted in any form or by any means electronic or mechanical including photocopying recording or any retrieval system without the written permission of the copyright holder LGC Limited 2005 All rights reserved Meeting the Traceability Requirements of 15017025 Analyst s Guide Third Edition September 2005 Editors Vicki Barwick and Steve Wood LGC Queens Road Teddington Middlesex TW11 OLY vam lgc co uk www vam org uk Preface to 3 Edition It is now two years since the second and most widely known edition of this guide was published During that time many more laboratory managers have become aware of the issues relating to traceable chemical measurement data Increased awareness has been accompanied by a rapid growth in the number of enquiries we receive concerning traceable chemical standards and matrix reference materials This is due in part but not entirely to the increasing attention being paid to th
6. PRINCIPLE The sample or the residue resulting from ashing is treated with hydrochloric acid SOP FDS 4 The elements iron copper manganese and zinc are determined after appropriate dilution by atomic absorption spectrometry APPARATUS In addition to normal laboratory apparatus the following is required 31 Volumetric flasks ee 33 Single element hollow cathode lamps for iron copper manganese and zinc 34 gt XXXIV Polythene bottles 250 mL Glassware must be of resistant borosilicate type and it is recommended to use apparatus which is reserved exclusively for trace element determination REAGENTS Introductory comments For preparation of the reagents and analytical solutions use water free from the cations to be determined obtained either by double distilling water in a borosilicate glass or quartz still or by double treatment on iron exchange resin The reagents must be of at least analytical grade Freedom from the element to be determined must be checked in a blank experiment If necessary the reagents must be further purified In determining trace elements it is important to be alert to the risks of contamination particularly by zinc copper and iron For this reason the equipment used in preparing the samples must be free of these metals To reduce the general risk of contamination work in a dust free atmosphere with scrupulously clean equipment and carefully washed glassware The determin
7. e to 3 decimal places from IUPAC tables www chem qmul ac uk iupac AtWt index html When reporting the results of the analysis carried out using the SOP the laboratory should state that all critical parameters used in the method are traceable to recognised national or international standards LGC VAM Traceability Guide 4 Other Examples Appendix 3 gives other examples of analytical procedures that have been evaluated for their traceability and degree of control requirements according to the approaches described in this Guide The analytical procedures concerned are l 2 SOP FDS 3 Sample Preparation by Dry Ashing SOP INS 1 Quantitative Analysis of Aqueous Extracts by Inductively Coupled Plasma Mass Spectrometry SOP FDS 2 Determination of Dimetridazole in Animal Feedingstuffs by High Performance Liquid Chromatography SOP ENV 1 Extraction of Metals from Soil by Aqua Regia SOP ENV 3 Determination of Water Soluble Sulphate in Soil SOP ENV 2 Determination of Common Anions in Waters by Ion Chromatography SOP CLIN 2 Analysis of Total Sodium from Serum by Atomic Emission Spectrometry SOP FDS 4 Determination of Ash in organic Matter and the Preparation of Aqueous Solutions for Quantitative Analysis SOP INS 2 Determination of the Trace Elements Iron Copper Manganese and Zinc in Solution by Atomic Absorption Spectroscopy 10 SOP INS 3 Electrogravimetric Determination of Copper LGC VAM Traceabili
8. 1 0 g of sodium chloride 4 1 into a TET 44 410 volumetric flask and make up to the mark with de ionised water 3 2 AS 7 2 Dilution of Solutions samples controls and standards Switch on the Hamilton Microlab 500 Diluter and set up for 1 in 45 dilution i e right syringe 220 uL sample left syringe 9780 uL diluent Ensure that the 10mL syringe 15 43 A3 installed Place the aqueous cesium chloride diluent 3 4 online and prime the diluter system to expel any air bubbles Dilute samples controls and standards into the respective tubes vortex and cap ready for the final dilution Dilute each sample control solution and standard solution a further 1 45 into respective labelled tubes using the same method vortex and cap ready for analysis Final dilution 1 2025 Note volumes and concentrations of standards and dilution rates of samples may change at the discretion of the Laboratory Manager 8 SAMPLE ANALYSIS Samples are analysed on the Varian FS220 AA Spectrometer according to the SOP Atomic Absorption Spectrometry Using the Varian FS 220 Spectrometer and the Varian SPS 5 Autosampler The burner probe wash bath and nebuliser disassemble the nebuliser must be clean prior to each analytical run The nebuliser must be cleaned where a change in diluent type takes place Place each component in an ultra sonic bath for at least at ina G7 G7 DO NOT place the magnetic float into the ultr
9. Filter the mixture through an oque transferred quantitatively to the filter paper ensuring that the precipitate is Wash the precipitate several times with hot water 4 1 until the washings are free from chloride as indicated by the absence of turbidity when a drop is tested with the solution of silver nitrate 4 11 Transfer the filter paper and precipitate to a previously ignited and weighed mj porcelain or silica crucible Place the crucible in an electric muffle furnace at room temperature and then raise the temperature gradually to red heat 800 C Hold the crucible at red heat for 15 minutes Transfer the crucible and contents to a desiccator and allow to cool to CALCULATION OF RESULTS The sulphate concentration C in the original test sample is calculated using the equation m m m x Vg MWso4 MWaasoa C mg kg x10 Wso4 molecular mass of sulphate 504 molecular mass of barium sulphate BaSO4 Check that the results obtained on the QC material are within the set limits NI G4 G1 G2 G2 G6 A4 A12 A7 G2 GI A4 A4 A4 A4 A4 AS AS R3 R3 LGC VAM Traceability Guide 7 6 SOP ENV 2 DETERMINATION OF COMMON ANIONS IN WATERS BY ION CHROMATOGRAPHY 1 SCOPE The method is applicable to the determination of fluoride chloride phosphate nitrate and sulphate in potable water swimming pool water and effluents 2 PRINCIPLE The
10. Mike Sargent LGC September 2005 Preface to Second Edition Many analysts are aware of the traceability requirements of ISO17025 These place the long standing practice of obtaining traceable calibrations for equipment such as balances or volumetric glassware on a more formal basis More importantly they extend this requirement to the chemical standards and reference materials used to calibrate or validate analytical methods Recent investigations carried out by LGC within the VAM programme have demonstrated the practical benefit of establishing the traceability of routine test results to chemical measurement standards of known quality Hence all laboratories regardless of whether their methods are accredited to ISO 17025 can benefit from implementing the principles needed to obtain traceable measurement results Unfortunately many laboratory managers have difficulty in envisaging how this can be done in a straightforward and cost effective manner This guide provides essential practical advice to analysts and laboratory managers on how to establish the traceability of their results to reliable and appropriate measurement standards Such traceability 1s the key to obtaining results that are fit for purpose particularly in terms of accuracy between laboratory comparability and consistency of data over periods of time Following the guidance given here should ensure compliance with the traceability requirements of ISO17025 The approach adopt
11. R7 A3 12 R A5 G6 A7 A7 A7 A3 R6 XV A5 A5 AS A5 A4 62 1 6 2 2 6 2 3 6 2 4 6 2 5 6 2 6 PROCEDURE NB During extraction and clean up stages care must be taken to ensure that the dichloromethane is not lost by evaporation 6 1 Preparation of QC Materials Weigh two 10 0 1 g portions of a previously tested blank feed into two separate conical flasks Record the weight to 0 001 g Add 200 pL of the spiking standard 3 17 to one of these test portions The second portion of blank feed is analysed as a blank Analyse these 2 samples along with the other samples comprising the batch from point 6 2 2 6 2 Extraction and Clean up Sample preparation all samples must be ground to pass a 0 5 mm sieve and mixed thoroughly prior to analysis Weigh between and 10 1g of the sample into a conical flask and record the weight to 0 001 g Add of phosphate buffer 3 12 using a measuring cylinder and allow to soak for about Using a pipette add 50 mL of dichloromethane 3 2 to the flask Stopper tightly and shake the contents of the flask vigorously by hand to ensure none of the sample is stuck to the bottom of the flask and that there are no large lumps present Follow this by shaking on a shaker for about If there is no evidence of an aqueous phase filter the extract through a filter funnel containing a little glass wool and collect approximately of the extract If the sample has s
12. CONTROL MATERIALS NEMA Normally the material most closely resembling the material under test will be analysed 5 SAMPLE PREPARATION A high degree of sample homogeneity is required to ensure that a truly representative sub sample can be taken Samples must be thoroughly homogenised using an appropriate blender or homogeniser The nature of the sample under analysis will determine which equipment should be used 6 ASHING METHOD 7 1 7 2 7 3 7 4 7 5 7 6 Heat quartz or platinum crucible 3 2 for at least in a drying oven Allow to cool in a desiccator for Weigh the crucible and record the weight Mo to 4 decimal places 28 of sample in the crucible 3 2 Record the weight Mj to 4 decimal Dry in an oven at KS Place the crucible into the cold muffle furnace 3 1 Close the furnace and gradually raise the temperature to 450 to 475 C over about Ashing must be carried out in a closed furnace without injection of air or oxygen Maintain this temperature for e g overnight to remove carbonaceous material and then open the furnace and allow to cool to about 8 The temperature indicated by the recorder must not exceed A2 A2 A2 G5 G5 G5 AI A4 G4 G4 A5 R8 R9I G2 G2 A4 10 A4 GI 12 7 G2 G2 GI A7 LGC VAM Traceability Guide 77 7 8 8 2 8 3 8 4 8 6 8 7 9 2 If the residue in the c
13. Content as KI ug tablet standardisation of sodium thiosulphate IKIO 6Na 23504 mass of KIO x Purity of KIO x1000 x 6 M mol litre MIO x volumeof Na 2550 3 Where T Titre mL B Blank titre mL M Molarity of sodium thiosulphate after standardisation mol L A mean weight of one tablet g mean of 20 tablets Ww weight of sample used g MWxi03 molecular mass of KIO molecular mass of KI Volume of Na5 0 5 5 AS R2 A4 A4 R3 R3 LGC VAM Traceability Guide 7 Appendix 3 Examples of Other SOPs NOTE These examples of SOPs have been compiled from various sources for the specific purpose of illustrating the principles of measurement traceability In the form they are written they are not intended for use on the bench The degree of control requirements for the various experimental values as indicated by the colour coding are based on group discussions at LGC and at a series of sector based workshops organised by LGC and held in July 2003 September 2004 and November 2004 The rationale for the choice of colour coding is given by an alphanumeric code which relates to one of the explanations given in appendix 1 The colour codings are provided for discussion purposes not as definitive and final answers Readers may well have their own views Generally only the first occurrence of a stated reference in an SOP is colour coded LGC VAM Traceability Guide VII 7
14. Identify the acceptable uncertainty in the final result i e the uncertainty that is consistent with the result being fit for purpose 3 Write down and understand the equation that is used in the SOP to calculate the final analytical result 4 Identify any reagents or equipment in the SOP with specified values 5 Identify the fixed experimental conditions used in the SOP 6 Allocate the values identified in steps 3 4 and 5 to either the green amber or red category depending on the degree of control that needs to be applied when that value is measured or realised in practice 7 Obtain any special stated references measurement standards i e those in the red category 3 2 Application of the Key Steps to the SOP 3 2 1 Steps 1 and 2 Method Selection and Acceptable Uncertainty For the purposes of this example it is presumed that the SOP has been validated and is applied within its stated scope step 1 Also the acceptable uncertainty in the final result is taken to be 5 step 2 Therefore the degree of control ideally required in any experimentally measured or realised values having a significant effect on the final result those in the amber and red category is 1 or better i e one fifth of the acceptable overall uncertainty see Section 2 3 1 LGC VAM Traceability Guide 11 3 2 2 Step 3 Equation Section 7 of the SOP gives the equation used to calculate the final analytical result For convenience the equation
15. a calibration curve by plotting the mean peak height values of all calibration standards versus the corresponding concentration value Using a suitable spreadsheet package construct a linear regression curve and determine A4 A4 A5 A8 A4 4 A4 G2 A5 G2 G4 G4 A5 G4 G4 AS G2 A7 N3 N3 LGC VAM Traceability Guide G4 R6 7 3 both the slope m and intercept c of the curve Sample Analysis When satisfactory repeatability has been obtained from repeated injections of the calibration standard injections of the QC solutions from 6 1 and sample solutions from 6 2 can be made All sample solutions are injected in duplicate An injection of a standard is made after every fourth sample such that the full range of standards 3 16 are incorporated into the sample extract sequence When necessary a measured aliquot of the sample extract solution should be diluted to a measured volume using the mobile phase 3 13 to ensure that the response does not exceed the response of the top calibration standard solution After injection of all the sample solutions two injections of each of the calibration standards should be made CALCULATION OF RESULTS The concentration x of the drug in the extract solution can be calculated from the equation using the expression X ug ml wo where im slope of calibration linear regression curve intercept of calibration linear regression
16. demonstrate their value to the chemical measurement laboratory Second to show how the VAM Traceability Guide provides a logical and straightforward way for a laboratory to examine its own standard operating procedures SOPs and assess when where and how to seek traceable calibrations or artefacts Comments from the participants in the workshops and the problems they experienced in trying to apply the guide proved to be a valuable learning experience for us as well We became convinced that whilst the guide had been widely welcomed there was an opportunity for further improvement These improvements to the third edition fall into two main areas We found that the exercises based on real SOPs were extremely useful in understanding how to apply the guide in the readers own laboratories We have therefore greatly extended the number and scope of the example SOPs so that all the main application areas are now addressed It was also apparent from the team exercises which formed a key part of the workshops that many analysts were distracted from the present purpose by discussing analytical aspects of the SOPs We have therefore reviewed all the examples and made them easier to use This has involved for example removing or simplifying some parts of the SOPs which whilst essential in applying the method for real only hinder the purpose for which we have provided them The other major change is to the worked example and the model answers pr
17. is also set out below The method uses a volumetric determination and is based on the equivalence 6Na S O0 T B x MxMW x10 x A Iodide Content as KI tablet ug 6x1000 x W Where T Titre mL B Blank titre mL M Molarity of sodium thiosulphate mol L A mean weight of one tablet g W weight of sample used equivalent to 20 tablets g MWh molecular mass of KI All experimental values in the equation will fall into either the amber or red categories as they all obviously have a direct and significant effect on the final result Therefore all of the values except the unit conversion factors 1000 10 and the volumetric equivalence factor 6 must be traceable to appropriate stated references The degree of control that the chosen stated reference must provide is 1 or better i e one fifth of the uncertainty that is acceptable in the final result see Section 2 3 1 The titre volumes T and B are measured using a burette A laboratory s QA system would normally be expected to provide volumetric glassware that conforms to a recognised specification e g BS846 ISO385 and is obtained from a reputable supplier Therefore provided this is the case the appropriate stated reference i e a burette for realising the titre volumes with an appropriate degree of control would fall into the amber category Examination of manufacturers specifications given in laboratory supply catalogu
18. lower range calibration line Aspirate the 0 5 mol L hydrochloric acid 4 3 used for dilution as a blank value Note that this is in addition to the 0 mg kg original sample blank When all the sample solutions have been run repeat the aspiration of the standards and check that the absorbance value of the highest concentration standard in the line is consistent with that obtained at the beginning of the run Place aspiration take up tube in the beaker of glass distilled water Carry out each measurement four times CALCULATION OF RESULTS For each element and each standard range used construct a calibration graph of absorbance versus concentration mg mL Carry out a linear regression analysis of the calibration data to obtain the slope m and intercept c From the observed absorbance y determine the concentration of each element of interest in the extract solution using the expression LGC VAM Traceability Guide A9 A9 R6 A5 R6 A5 A5 R6 A5 A5 R6 A5 A5 G2 XXXVII Kineta Au 1 The concentration of the element in the original material can then be calculated from G where concentration of element i in solution mg mL E measured absorbance for element i in sample A6 slope from linear regression analysis R10 Ya measured absorbance for blank sample for element I A6 G concentration of element i in sample mg g V final volume
19. lt 20 uS cm If it is not replace the eluent Load portions aem of the samples calibration standards and QC material into polyvials up to the mark Place the polyvials in the autosampler Calibration standards are placed at the start of a run and at about every 20 sample vials In each run there should be at least one QC material and one replicate test sample Set up a file for the acquisition of data from the chromatography run To verify the system is operating correctly firstly run a mixed calibration standard The peak areas and retention times should be comparable to those obtained in previous runs The retention time of the sulphate peak should be within 1 minute of that observed in previous runs Provided the system is working satisfactorily run the complete set of polyvials If the area of a sample peak exceeds that of the top calibration standard dilute a measured aliquot to a known volume to bring the sample peak area within the calibration range and re inject the diluted sample 8 CALCULATION OF RESULTS Using the data station process the raw peak data to obtain the calculated anion concentrations in the samples and the QC material The data station processes the data using an equation of the following type A sample C catibstd es A xF calibstd where concentration of anion in sample mg L concentration of anion in calibration standard mg L LGC VAM Traceabi
20. or fixed conditions to be identified The SOP must be carried out in a manner that establishes the traceability of these values to appropriate stated references For this purpose the analyst must then carry out step 4 and obtain the appropriate stated references The issues involved in this approach are discussed below 2 2 Appropriate Stated References 2 2 1 What are Stated References Put simply a stated reference is any reference point that an analyst uses to measure obtain or realise a particular experimental value in practice Some examples of stated references and their potential applications are tabulated below LGC VAM Traceability Guide 3 Typical Examples of Stated References Stated reference Balance Standard weight Pipette burette graduated flask or other volumetric glassware Automatic pipette Measuring cylinder Graduated syringe Hg in glass thermometer Platinum resistance thermometer Clock or stopwatch UV optical IR filter Buffer solution Sieve Filter paper membrane filter sintered glass filter Published tables and compilations of physical chemical data Pure chemical or solution prepared from a pure chemical Certified reference material comprising a pure chemical or a solution of a pure chemical Commercial chemical with a producer s stated specification Could be used to provide traceability for practical realisations of the following values mass mass volume volume vol
21. or international standards However whilst national and international standards exist for physical measurements such as mass i e the international standard kilogram there are currently no such standards for chemical measurements For example if we were to analyse a sample of drinking water for lead content we would soon find that there is no national or international measurement standard for lead Given this situation the task of the analyst is to chose for use as measurement standards stated references that are appropriate for the particular analysis that is to be carried out To identify appropriate stated references for traceability purposes a systematic approach should be adopted Section 2 of this guide suggests an approach that was the subject of two user workshops and which was found to be useful and workable by the participants Having completed an evaluation of the traceability for each critical parameter the analyst should prepare an appropriate traceability statement which may be written into the SOP itself or the validation report When reporting the results of an analysis carried out using the SOP it will usually be sufficient for the laboratory to state that all critical parameters used in the method are traceable to recognised national or international standards 1 International Vocabulary of Basic and General Terms in Metrology ISO Geneva 1993 2 edition ISBN 92 67 01075 1 LGC VAM Traceability Guide 2 Practi
22. sample is injected onto an ion exchange chromatography column and eluted with an aqueous carbonate bicarbonate mobile phase The anions are detected and quantified using a conductivity detector 3 APPARATUS In addition to normal laboratory glassware and equipment the following 1s required 3 1 Dionex DX 500 Ion Chromatograph 4 REAGENTS 41 Ultra pure water Elgastat UHP water with a conductivity 0 1 uS cm a2 42 Sodium carbonate A2 4 3 Sodium bicarbonate A2 4 4 Mobile phase 1 8 mM sodium carbonate 1 7 mM sodium bicarbonate Weigh ms 4 2 and 0 710 0 005 g sodium bicarbonate 44 4 3 into a Add water 4 1 to dissolve the salts make to the 45 mark with water 4 1 and mix 5 CALIBRATION STANDARDS 5 1 Pure Substances used to Prepare Calibration Standards R R6 R R6 5 1 5 Potassium sulphate R6 5 2 Stock Standard Solutions The following stock standard solutions are prepared by dissolving the stated quantity of each particular compound in water 4 1 The solution is transferred to a 1 litre AS Which 1s then made to the mark with water 4 1 and inverted several times to mix the contents LGC VAM Traceability Guide XXIII Concentration of anion in stock solution mg litre Anion Fluoride Chloride Nitrate Phosphate Sulphate 5 3 Mixed Stock Solution Using glass pipettes transfer the following aliquots of each of the single stock solutions make up to the mark with water 4 1 and mix
23. select a properly validated method as per step 1 Section 3 1 Step 4 Identify Reagents and Equipment in the SOP with Specified Values a Equipment with Specified Values Section 3 of the SOP Appendix 2 lists the equipment requirements and examination of these shows that certain values are specified e g e Fused silica crucibles 50 mL capacity 57 mm diameter e Whatman filter paper 541 18 5 cm diameter However an experienced analyst will readily appreciate that these values are generally provided for indicative information purposes only They clearly will have no significant effect on the final analytical result Only minimal control is required in the realisation of these values They are therefore allocated to the green category LGC VAM Traceability Guide b Reagents with Specified Values Section 4 of the SOP lists the reagent requirements and many of these specify values or other information regarding the reagent e g e Purified water e Phenol 80 w w reagent grade e Phenol solution 5 v v e Bromine reagent grade e Potassium carbonate reagent grade e Orthophosphoric acid 88 reagent grade e Potassium iodate reagent grade e Sodium thiosulphate 0 1 mol L analytical volumetric solution Certain of the specified values clearly refer to chemical reagents that are produced and sold by commercial manufacturers such as phenol 80 w w reagent grade and sodium thiosulphate 0 1 mol L analytical volum
24. sludge amended soil R9 GC6135 Brick works soil R9 IST SRM2710 Montana soil R9 5 APPARATUS In addition to normal laboratory glassware and equipment the following is required 5 1 Reflux condenser assembled length with ground glass joints G6 52 150 pm sieve 6 SAMPLE PREPARATION The soil must be air dried and ground to pass a 150 um sieve 5 2 and then mixed A8 XVIII LGC VAM Traceability Guide 7 3 7 5 7 6 Tf 7 9 SAMPLE EXTRACTION PROCEDURE Note With each batch of 10 soil samples a reagent blank and a soil QC sample 4 must be run 7 1 Weigh 3 00 0 01 g of the prepared sample into a reaction vessel 7 2 Moisten the soil with 2 0 0 1 mL of water 3 1 Using a measuring cylinder add 8 of hydrochloric acid 3 3 followed by ETSE of nitric acid 3 2 dropwise if necessary to reduce foaming 7 4 Allow to stand overnight at Add of 0 5 mol L nitric acid 3 4 to the absorption vessel and connect the absorption vessel to the reaction vessel via the reflux condenser 5 1 Heat the soil acid mixture under reflux for 2 hours 5 minutesh ensuring that the condensation zone is lower than of the height of the condenser Add the contents of the absorption vessel to the reaction vessel via the condenser by rinsing the absorption vessel with portions of 0 5 mol L nitric acid 3 4 7 8 Filter the contents of the reaction vessel into a Buchner flask Rinse the reaction ve
25. that a less stringent degree of control would be fit for purpose Summary The outcome of the above discussion is summarised in the table below in which each of the values referred to in equations 1 and 2 are assigned to the colour category which identifies how the appropriate degree of control may be obtained Value in Equation Colour Minimum Action Required by Category Analyst to Obtain the Appropriate Stated References T Titre mL Amber Use volumetric glassware B Blank titre mL Use volumetric glassware mean weight of one tablet g Use analytical balance 4 fig Use top pan balance 2 fig B e Wxio3 molecular mass of KIO Calculate to 3 d p using up to date tables Wx molecular mass of Red Calculate to 3 d p using up to r a date tables Molarity of Na S O Red Standardise using KIO Mass of KIO g Amber Use analytical balance 4 fig Purity of KIO Red Choose reagent with required purity and uncertainty Amber Use volumetric glassware The table above reinforces the earlier comments that values appearing in the equation will always fall in either the amber or red categories since they all have a direct and significant effect on the final analytical result It is important to note that the equation must always be written out in full and explicitly Occasionally SOPs will be found with equations in a shortened form For example dilution factors unit conversion factors and cer
26. the ashed sample is made up to mL AS F dilution factor if applicable AS M sample weight g taken for digestion SOP FDS 4 A4 12 REPEATABILITY The difference between the results of two parallel determinations carried out on the same sample by the same analyst should not exceed 5 mg kg in absolute value for contents of the trace element concerned not greater than 50 mg kg 10 of the higher result for contents of the trace element concerned greater than 50 but not greater than 100 mg kg 10 mg kg in absolute value for contents of the trace element concerned greater than 100 but not greater than 200 mg kg 5 of the higher result for contents of the trace element concerned greater than 200 mg kg 13 PRECISION AND BIAS Precision and bias figures for the method based upon six replicate analyses of R9 reference materials The replicate analyses were performed upon the same day Certified standards are routinely analysed as quality control check samples with each batch of samples as detailed in the procedure XXXVIII LGC VAM Traceability Guide 7 10 SOP INS 3 ELECTROGRAVIMETRIC DETERMINATION OF COPPER 1 PURPOSE AND SCOPE The method is for the quantitative electrogravimetric determination of copper in copper concentrates The method is applicable to samples containing 15 45 copper and less than 2 arsenic 2 PRINCIPLE The sample is dissolved in perchloric acid silver and lead are precipitated and all insol
27. therefore allocated to the green category The degree of control required when obtaining the specified furnace temperature depends on the effect departures from the specified value will have on the final analytical result As discussed in Section 2 3 2 information obtained from method validation work may be helpful in addressing such issues In general terms if the ignition temperature is too low there may be incomplete release of the KI from the tablet matrix Conversely if it is too high losses by volatilisation may occur The fact that the SOP specifies a temperature range of 675 C to 700 C suggests that an actual temperature of 687 C 12 C should be appropriate A degree of control of 12 C should be readily obtainable using the temperature read out device attached to the muffle furnace It would be sensible to verify the accuracy of this read out say on a yearly basis by making a cross check with a calibrated device such as a platinum resistance thermometer The provision and use of formally calibrated reference thermometers for checking the performance of working thermometers is an activity that would normally be covered by a laboratory s QA system Stated references for temperature measurement are therefore allocated to the amber category LGC VAM Traceability Guide 3 2 5 3 2 6 If a laboratory s QA system does not provide calibrated reference thermometers the analyst will have to make special arrangements when reali
28. 1 SOP FDS 3 SAMPLE PREPARATION BY DRY ASHING 1 SCOPE AND PRINCIPLE The method applies to the quantitative analysis of trace elements of nutritional importance in food and biological materials It is not suitable for oils and fats and special care is required for foods with high fat or sugar content The method is applicable for the following elements Na K Ca Mg P Cu Fe Mn and Zn The method involves the removal of organic matter by controlled combustion in a muffle furnace the inorganic residue being dissolved in hydrochloric acid solution ready for analysis by inductively coupled plasma mass spectrometry SOP INS 1 2 APPARATUS In addition to normal laboratory apparatus the following is required 2 Muffle furnace 0 1000 C model A3 22 Silica dishes Sess each is uniquely labelled before use by burning ona G6 code number written with a wax pencil Only dishes that are not chipped scratched or otherwise damaged may be used 23 Tilt measures 5 mL and 10 mL G4 All glassware and plastic vessels should be cleaned before use by rinsing with 5 nitric acid 3 5 followed by thorough rinsing with purified water 3 4 2 4 Tongs N2 3 REAGENTS A2 A2 Hydrochloric acid solution 50 v v aq prepared by diluting 3 2 with 3 4 and CA A2 GS Nitric acid 10 v v aq prepared by diluting 3 1 with 3 4 G5 4 QUALITY CONTROL MATERIALS
29. 2 2 1 What are Stated References esee eene eren enne enne 3 2 2 2 Whatis eee peteretur rese bees e e Dea nee ap ue 5 2 3 CHOOSING THE APPROPRIATE DEGREE OF CONTROL ee e e ee eene 6 2 3 1 Fitness for Purpose Criteria eee t e esee ere A russi eit RU 6 2 3 2 Method Validation Data ic rreren ose E a ER E enne eren nee nnns 7 2 3 3 Uncertainty Data inie c ee eret ere epe aeee aa ee e eiA 7 2 3 4 ANGIYSIS Experience 7 2 4 OBTAINING THE APPROPRIATE DEGREE OF CONTROL e ee e n en ee nenne 8 2 4 1 Green Category Lu ria enean ET ien uda letersi 8 2 4 2 Amber COLOR OPV ales 9 2 4 3 Red CALC SONY i ebd rete qp e Shot bd rhon Bet 9 3 IDENTIFYING THE TRACEABILITY REQUIREMENTS FOR A STANDARD OPERATING PROCEDURE AN EXAMPLE esee eene aeneo ao Hoe ne sie erac epae vete pa deus oen oo iege d epa epu ea ee pe dee rao varese pego 11 3 1 _ KEY STEPS IN THE ATTAINMENT OF TRACEABILITY eee e ee e een en een ene 11 3 2 APPLICATION OF THE KEY STEPS TO THE SOP ee n een en een enne 11 3 2 1 Steps 1 and 2 Method Selection and Acceptable Uncertainty sss 11 3 2 2 SLED DS Equations 12 3 2 3 Step 4 Identify Reagents and
30. 2 tandardised solution R3 olecular masses calculate from tables R4 specified reagents not covered by laboratory QA procedures R5 nternal quality control solutions Run with each batch analyst must decide on suitable material R6 Used for calibration R7 Used for quality contro R8 OC materials analyst must decide R9 eference materials analyst must decide R10 xperimentally determined value 1 LGC VAM Traceability Guide 6 Appendix 2 Worked Example This SOP is discussed in detail in section 3 of the guide NOTE This example of an SOP has been compiled from various sources for the specific purpose of illustrating the principles of measurement traceability In the form it is written it is not intended for use on the bench The degree of control requirements for the various experimental values as indicated by the colour coding are based on group discussions at LGC and at a series of sector based workshops organised by LGC and held in July 2003 September 2004 and November 2004 The rationale for the choice of colour coding is given by an alphanumeric code which relates to one of the explanations given in appendix 1 The colour codings are provided for discussion purposes not as definitive and final answers Readers may well have their own views Generally only the first occurrence of a stated reference in the SOP is colour coded LGC VAM Traceability Guide 6 1 SOP FDS 1 DETERMINATION OF POTASSIUM IODIDE IN VIT
31. 7 A4 G4 G1 G4 G7 A10 A4 G4 G7 10 A4 G4 G4 LGC VAM Traceability Guide 4 11 5 5 1 5 2 6 6 1 6 1 1 6 1 2 6 2 6 2 1 6 2 2 6 2 3 6 2 4 6 2 5 6 2 6 6 3 6 3 1 6 3 5 6 3 6 6 3 7 glass or polythene bottle Silver nitrate solution 919899 Dissolve of silver nitrate 4 5 in about 4 1 and dilute to Ti eateries G with water 4 1 Transfer the solution to an amber glass bottle and store in the dark QUALITY CONTROL MATERIALS Either of the following may be used as a quality control material A previously analysed soil sample CRM may be used OEE 011 PROCEDURE Sample Preparation The soil sample must be air dried according to SOP ENV 1A ground to pass a 2mm sieve 3 4 and mixed A quality control material 5 must be included with each batch of samples Extraction of Samples Extractions should be carried out at a temperature in the range 20 C to 25 C A reagent blank must be included with each batch of samples Transfer 10 0 1 6 of the prepared sample to an extraction bottle Add of water 4 1 to the extraction bottle and stopper tightly Place the extraction bottle on the mechanical shaker 3 1 and agitate for nme Centrifuge the soil suspension and filter the supernate under vacuum through a suitable filter paper 3 2 into a Buchner flask Measure the volume of the filtrate and retain the filtrate for determination of
32. 9 G3 G4 G4 XLI 9 2 10 trace elements iron copper manganese and zinc in solution by Atomic Absorption Spectroscopy EXPRESSION OF RESULTS Calculation Concentration ppm Cu by AAS 10 000 C Total Cu E oae Cu by AAS x5 Weight of Cathode after deposition A4 gl Weight of Cathode before deposition A4 Ww Sample Weight g A4 R10 TEST REPORT Worksheets should include the following e Method of analysis used method code e Variations of sample or deviations from standard method of analysis e Clear identification of personnel weighing and checking also dated e Certified level of reference material being used with tolerance levels e Range of element normally anticipated for this grade of sample Reporting sheet should include the following e Date of reporting e Units element being reported e Analysis state all corrections to be indicated e Sample reference corresponding to element value e Remarks to be short and concise e Method code MEASUREMENT OF UNCERTAINTY The measurement of uncertainty for this procedure will be twice the standard deviation calculated from the performance of the regular quality control data collected where the data 1s available For the current value refer to the quality control data review file LGC VAM Traceability Guide
33. A5 A2 A2 A4 NI AS A2 G5 IV LGC VAM Traceability Guide Prepare in a fume cupboard Prepare by diluting of orthophosphoric acid 4 6 to of water 4 1 in a measuring G4 cylinder Transfer to a suitable container and mix well before use 47 indicator A2 4 8 Potassium iodate reagent grade RI A2 Sodium thiosulphate 0 01 R2 Pipette 50 mL of sodium thiosulphate 4 9 into a Make up to A5 volume with water stopper flask and mix well Signs RI OUS EI The method used is that detailed in Quantitative Inorganic Analysis A I Vogel fourth edition page 375 5 SAMPLE PREPARATION 5 1 Weigh 20 tablets to four decimal places using an analytical balance and record the weight Calculate the mean tablet weight A4 53 Grind the above 20 tablets plus another 20 tablets as finely as possible using a pestle and mortar 6 METHOD The analysis is carried out in duplicate for each batch of tablets blank determination omitting the sample is also carried out 6 1 Using long tongs place crucible and lid in a muffle set at 8 for X GI G2 ol to Remove immediately from muffle place on a heatproof mat and co GI emp erature 6 2 Weigh to four decimal places a sample weight equivalent to twenty tablets into a dry A4 crucible 6 3 Add 7g of anhydrous potassium carbonate 4 4 mix carefully and gently tap the A4 crucible several times to compact the m
34. AMIN TABLETS 1 SCOPE The method is for the analysis of potassium iodide in multivitamin tablets where the potassium iodide is in the range 117 143 pg tablet 2 PRINCIPLE The tablets are ashed to remove any organic impurities and to free the potassium iodide The ashed sample is then extracted with boiling water and the potassium iodide is converted to potassium iodate by reaction with bromine water Phosphoric acid is added to liberate excess bromine which is then removed by boiling Iodide is added to react with the iodate to yield iodine The free iodine is then determined by titrating against a standardised solution of sodium thiosulphate 3 APPARATUS In addition to normal laboratory equipment the following is required Fused silica crucibles with lids 50 mL capacity 57 mm diameter Filter paper Whatman No 541 18 5 cm diameter 3 3 Muffle furnace 4 REAGENTS Phenol solution 5 v v Prepare by diluting of phenol 4 2 with water 4 1 to in a measuring cylinder Transfer to a suitable container and mix well before use Prepare in a fume cupboard Pipette 1 mL of bromine 4 3 into a 50 mL volumetric flask Make up to volume with water 4 1 stopper and mix well 4 5 1 Weigh approximately l6g of potassium iodide 4 5 into a 50 mL beaker Transfer to a 100 with water 4 1 Make up to volume with water 4 1 stopper flask and mix well G6 G6 A2 A2 G5 G4 A2 A2
35. Equipment in the SOP with Specified Values 16 3 2 4 Step 5 Identify the Fixed Experimental Conditions used in the SOP sss 18 3 2 5 Equipment and Reagents with Specified Values with no impact on the Traceability 19 3 2 6 Step 6 Traceability Statement esee 19 4 OTHER EXAMPLES eee eerie epe d o rede Pier oun been n 21 BIBLIOGRAPHY D M EN 22 5 APPENDIX 1 RATIONALE FOR TRACEABILITY CATEGORY ASSIGNMENT I 6 APPENDIX 2 WORKED EXAMPLE tn ee en st tn stint tn stats toss toss toss ease tps etas e ease ense ta ata 6 1 SOP FDS 1 DETERMINATION OF POTASSIUM IODIDE IN VITAMIN TABLETS IV Te APPENDIX c 7 1 SOP FDS 3 SAMPLE PREPARATION BY DRY ASHING 7 2 SOP INS I QUANTITATIVE ANALYSIS OF AQUEOUS EXTRACTS BY INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY eee renneneen enne XI 7 3 SOP FDS 2 THE DETERMINATION OF DIMETRIDAZOLE IN ANIMAL FEEDING STUFFS BY HIGH PERFORMANCE LIQUID XIV 7 4 SOP ENV 1 EXTRACTION OF METALS FROM SOIL BY AQUA REGIA XVIII 7 5 SOP ENV 3 DETERMINATION OF WATER SOLUBLE SULPHATE IN SOIL XX 7 6 SOP ENV 2 DETERMINATION OF COMMON ANIONS IN WATERS BY I
36. ON CONTENTS 2 rte rh dett EE Permit Ot o Tt Aged ees XXIII 7 7 CLIN 2 ANALYSIS OF TOTAL SODIUM FROM SERUM BY ATOMIC EMMISSION SPECTROMETRY eere ERR eon n ie ep ree TH na E erre everest XXVII 7 8 SOP FDS 4 DETERMINATION OF ASH IN ORGANIC MATTER AND THE PREPARATION OF AQUEOUS SOLUTIONS FOR QUANTITATIVE ANALYSIS XXXI 7 9 SOP INS 2 DETERMINATION OF THE TRACE ELEMENTS IRON COPPER MANGANESE AND ZINC IN SOLUTION BY ATOMIC ABSORPTION SPECTROSCOPY 7 10 SOP INS 3 ELECTROGRAVIMETRIC DETERMINATION OF COPPER XXXIX LGC VAM Traceability Guide 1 Introduction 1 1 Why is Traceability Important All chemical measurement results depend upon and are ultimately traceable to the values of measurement standards of various types such as those for mass volume and the amount of a particular chemical species If results obtained by different laboratories are to be comparable it is essential that all results are based on reliable measurement standards whose values are linked to a stated reference If there are differences in the quality of the measurement standards used in different laboratories discrepancies will inevitably arise when different laboratories analyse the same sample Recent investigations carried out within the VAM programme have shown the practical benefit of establishing the traceability of routine test results to measurement standards of known quality In an
37. Platinum cathode and anode Laboratory stirrer 3 bank with retort rods Whatman No 540 filter papers 11 cm Whatman No 541 filter papers 12 5 cm Whatman No 541 filter papers SAMPLING AND SAMPLES Laboratory Sample The sample should appear fine enough to pass through a 60 mesh 250 um sieve Any oversize particles are crushed to the correct mesh size Thoroughly mix and blend Preparation of the test sample Take sufficient mass of the laboratory sample for the required chemical analysis and transfer to a jar Heat in the laboratory oven at 105 2 C for 2 hours Remove from the heat and replace screwcap Allow to cool PROCEDURE Number of Determinations Carry out determinations at least in duplicate as far as possible under repeatability conditions on each test sample Taking several increments weigh accurately to the nearest 0 0001 g approximately 2g of test sample 6 2 into a 400 mL squat form beaker Dissolution of sample Add a few anti bumping granules and of perchloric acid 3 8 heat on a high R8 A3 G6 G6 A7 AS G6 G6 G6 A3 or A8 G2 10 10 NI LGC VAM Traceability Guide 7 4 7 4 1 7 4 2 7 4 3 7 4 4 7 5 7 5 1 temperature hotplate 5 2 until dense white fumes of perchloric acid appear Allow to cool Note Fume in a fume cupboard fitted with a constant backflow of water under no circumstances allow to fume dry Always use beaker tongs Remo
38. a sonic bath as G7 this will affect the magnetic properties Rinse burner probe wash bath and nebuliser in purified water 3 2 and re install onto the FS 220 Clean the inlet of the nebuliser with a fine wire Fill the probe wash bath with purified water containing 1 Triton X 100 3 1 Place the lamp 2 2 into the appropriate position and align the lamp to give the maximum signal this lamp is used for alignment of the burner head only The instrument must be fully optimised prior to analysis in particular burner height 2 75 mm height A7 may be adjusted away from this if deemed necessary by the Laboratory Manager and alignment and nebuliser uptake Prior to sample analysis run a set of standards and compare absorbance levels with previous runs If the absorbance level for each standard is considerably lower than previous analyses and the length of time for data acquisition is slow set at a maximum of 10 seconds consider re optimising the nebuliser uptake rate At the start of the run include 14 blank samples water only to enable the temperature of the burner to reach its optimum before sample analysis commences Standard curves are run after each batch of 10 samples with analytical data read from the previous curve Instrument parameters are given below Sodium LGC VAM Traceability Guide XXIX 9 1 9 2 XXX Instrument Mode Flame Emission Sampling Mode Autonormal Flame Type Air acetylene Air Fl
39. alysis by AA spectroscopy by the method SOP FDS 4 Determination of ash in organic matter and the preparation of aqueous solutions LGC VAM Traceability Guide R6 A2 G5 G5 A2 G5 A2 G6 G6 A4 G4 A5 A4 G4 A5 A4 G4 A5 A4 A2 G4 R6 G4 R6 R6 G4 A5 A4 R6 G4 AS R8 XXXV for quantitative analysis All glassware used in the preparation of the standard solutions must be soaked in dilute nitric acid for at least 12 hours and then rinsed thoroughly with purified water 4 1 prior to use 8 1 Preparation of calibration solutions The resulting sample solutions must be free of any suspended particulate matter If necessary filter the sample solution through an ash free filter paper For each of the elements to be determined prepare from the standard solutions given in points 5 1 5 2 5 3 and 5 4 Each calibration solution to R6 have an concentration of about P in the cases of iron manganese and G7 zinc a lanthanum chloride concentration equivalent to G7 The trace element concentrations selected must lie within the range of sensitivity of the spectrophotometer used 8 2 Preparation of solution for analysis Solutions for analysis are prepared according to procedure SOP FDS 4 8 3 Blank experiment The blank experiment must include all the prescribed steps of the procedure except that the sample material i
40. any suggestions from the workshop participants and we are grateful for their help We are also grateful to the Eurachem CITAC Working Group for early access to their draft document This work was supported by the Department of Trade and Industry s Valid Analytical Measurement Programme VAM Mike Sargent LGC September 2003 Acknowledgements Richard Lawn Mike Sargent and Alex Williams were closely involved in the design and preparation of this guide together with the workshops that formed an integral part of its production We are also grateful to the many analysts managers experts on traceability and representatives of accreditation bodies who provided advice and comments on drafts of the guide A special word of thanks to all the workshop participants whose contribution played a major role in shaping the guide and who are now too numerous to list This work was supported by the Department of Trade and Industry s Valid Analytical Measurement Programme VAM LGC VAM Traceability Guide Ts INTRODUCTION P 1 ll WEYI ERACEABIEITY IMPORTANT casser TRE ERREUR age dione Rer 1 1 2 TRACEABILITY IN CHEMICAL MEASUREMENTS 1 2 PRACTICAL ATTAINMENT OF 3 2 OVERVIEW ence E Eee Pe pe T ei P Eee 3 2 2 APPROPRIATE STATED REFERENCE Sune aceae ae tenente nnne teen tienne tiere tette nente 3
41. ate stated reference to establish the traceability of the sodium thiosulphate molarity value M in equation 1 It is considered unlikely that a stated reference would be provided by a laboratory s QA system This value is therefore allocated to the red category Values for molecular masses MW appear in both equations 1 and 2 The analyst will need to adopt appropriate values for these This is a straightforward matter simply requiring up to date tables and an accurate addition of the component atomic weights Calculation to three decimal places will provide molecular weight values with an uncertainty of 0 1 which will be fit for purpose for use in virtually all SOPs Because the analyst is required to do the calculations it is considered unlikely that the laboratory s QA system would provide molecular weight values they are allocated to the red category Measurements of mass also appear in both equations 1 and 2 A tablet weight A of the order of 1 g should be measurable to about 0 0004 g on a 4 figure analytical balance This corresponds to a degree of control in the measurement of such mass values of about 0 04 which is more than adequate for the purposes of this example In contrast a 2 figure top pan balance would be expected to provide an uncertainty of about 0 04 g equivalent to a degree of control of 4 which is not fit for purpose The combined mass W of 20 tablets about 20 g taken for the actual analysis could
42. ation of zinc is particularly sensitive to many types of contamination e g from glassware reagents dust etc AS A3 All NI LGC VAM Traceability Guide In place of the standard solutions described below appropriate SUI itus may be used 4 7 Acetylene gas Compressed air taken from the piped system within the laboratory 4 9 Lanthanum chloride solution Dissolve 12g of lanthanum oxide in of water 4 1 add of 6 mol L hydrochloric acid 4 2 and make up to 4 1 CALIBRATION STANDARDS 5 1 Standard iron solution 1 000 ug Fe mL Dissolve 1 g of in of 6 mol L hydrochloric acid 4 2 add of hydrogen peroxide 4 6 and make up to one litre with water 4 1 Un 52 Standard copper solution 1 000 ug Cu mL D mad of IJSEI SC Bin in of 6 mol L hydrochloric acid 4 2 add of hydrogen peroxide 4 6 and make up to one litre with water 4 1 5 3 Standard manganese solution 1 000 ug Mn mL Dissolve 1 g of in of 6 mol L hydrochloric acid 4 2 and make up to 4 1 5 4 Standard zinc solution 1 000 ug Zn mL Dissolve 1 g 1 of 6 mol L hydrochloric acid 4 2 and make up to 6 QUALITY CONTROL MATERIALS A variety of quality control materials are available 7 VALIDATION OF INSTRUMENT PERFORMANCE The instrument must be set up and its performance validated as described in the manufacturer s user manual 8 SAMPLE PREPARATION Solid food samples are prepared for an
43. ation of element in the aqueous extract ng mL Calin concentration of element in the prepared calibration standard ng mL R6 A6 A6 A6 A6 AS The software also automatically corrects for isobaric interferences However all concentrations reported on each isotope should be checked for polyatomic interferences or residual isobaric interferences Care should always be exercised when interpreting results 11 BIAS AND PRECISION Short term precision is typically 2 relative Accuracy is checked using either certified reference materials or the method of standard additions as described in the users manual SS GR NENS 5 1 from a source different to that used to prepare R8 the calibration standards 8 3 may be suitable as CRMs for the purposes of checking bias LGC VAM Traceability Guide XIII 7 3 SOP FDS 2 THE DETERMINATION OF DIMETRIDAZOLE IN 3 1 34 3 5 3 7 XIV ANIMAL FEEDING STUFFS BY HIGH PERFORMANCE LIQUID CHROMATOGRAPHY SCOPE This method specifies a procedure for the determination of dimetridazole in animal feeds The lower limit of determination is 1 mg kg 2 PRINICIPLE The analyte is extracted from the sample with dichloromethane The extract is cleaned up on a silica cartridge and the analyte quantified using reverse phase high performance liquid chromatography using ultra violet UV absorbance detection 320 nm 3 REAGENTS NB Unless otherwise specifi
44. be measured to within 0 2 on a 2 figure top pan balance which is fit for purpose A 4 figure analytical balance would also of course be fit for purpose Therefore balances properly calibrated and maintained as part of a laboratory s QA system and properly selected by the analyst will provide the necessary degree of control for the mass measurements They are therefore allocated to the amber category Similar considerations show that 1f the KIO stock solution used in the standardisation of the sodium thiosulphate equation 2 is prepared using a 4 figure analytical balance an adequate degree of control will be obtained A known aliquot volume of this solution is then taken using volumetric glassware a pipette The term mass of KIO in equation 2 1s actually the product of the concentration of the stock solution and the aliquot volume taken As discussed previously in relation to the use of burettes appropriate volumetric glassware for realising volumes will normally be provided by the laboratory s QA system LGC VAM Traceability Guide Special Note Where an SOP gives a specific instruction as to the degree of control required in a particular step such as e weigh on a 4 figure balance e use calibrated volumetric glassware with an individual certificate e calibrate the instrument with NIST SRM 3108 Cd solution in HNO 9 12 0 03 mg g this degree of control must be applied even if the considerations discussed above indicate
45. bumping granules nitric acid 3 7 and allow to stand until the reaction has ceased Boil to expel oxides of nitrogen remove from the hotplate add sulphuric acid 3 15 sodium chloride solution 3 12 and dilute to ee with water 3 1 Note Whilst using nitric acid wear gloves and perform all parts of the procedure which releases fumes of nitrous oxide under fume extraction Add of potassium permanganate solution 3 10 and a magnetic stirring bar and electrolyse for 65 minutes at 1 5 amperes 5 6 onto a weighed platinum cathode 5 4 Record cathode weight as Cl If oxides of nitrogen start to be evolved during electrolysis carefully add of sulphamic acid 3 13 When the electrolysis is complete rinse the cathode with water 3 1 methanol 3 5 and acetone 3 2 dry and reweigh cathode weight C2 Retain the electrolyte Treatment of residues and analysis by Atomic Absorption Spectroscopy To the combined filter papers in the original beaker retained in step 7 4 4 add of nitric acid 3 7 and of perchloric acid 3 8 and fume on a high temperature hotplate 5 2 Allow to cool Transfer to a 1 litre volumetric flask step 7 5 2 add the electrolyte retained in step 7 5 6 dilute to volume with water and mix well Determine copper content by AAS using method SOP INS 2 Determination of the LGC VAM Traceability Guide G4 G4 G4 G4 G4 NI G3 G2 G4 G4 G4 G4 G4 A13 A7 A
46. cal Attainment of Traceability 2 1 Overview Based on the approach described in the Eurachem CITAC Guide the analyst must undertake the following tasks as a pre requisite to obtaining traceable measurement results when carrying out a particular analytical method or standard operating procedure SOP 1 Write down and understand the equation used to calculate the analytical result Identify any reagents or equipment with specified values Identify the fixed experimental conditions used in the SOP Tels Obtain appropriate stated references measurement standards for use in the practical measurement or realisation of the experimental values identified in 1 2 and 3 Additionally it is important to note that the SOP concerned must have been properly validated and must be applied within its stated scope If these conditions are not met an erroneous result may still be produced even if all of the measurements and values referred to in the SOP are carried out or realised in a traceable manner Guidance on method validation is beyond the scope of this document but further information may be found in The Fitness for Purpose of Analytical Methods A Laboratory Guide to Method Validation and Related Topics www eurachem ul pt Before commencing the analysis therefore the analyst must first review the SOP and carry out steps 1 2 and 3 This will enable those values which appear in the equation or are specified in the reagents equipment
47. curve The concentration of dimetridazole can then be calculated from Ax VxF M G where G dimetridazole content in sample mg kg concentration of dimetridazole in injected sample solution ug mL LGC VAM Traceability Guide 6 R10 R10 R10 AS AS A4 XVII 7 4 SOP ENV 1 EXTRACTION OF METALS FROM SOIL BY AQUA REGIA 1 SCOPE The method is applicable to soils containing not more than 33 m m of organic matter 2 PRINCIPLE The sample is extracted using a hydrochloric acid nitric acid mixture under specified conditions BS7755 ISO11466 1995 The extraction procedure does not necessarily extract the total metal content 3 REAGENTS All reagents should be of at least analytical grade They are obtainable from major chemical suppliers unless otherwise stated 3 1 Water demineralised a2 32 Nitric acid 69 v v SG 1 42 a2 33 Hydrochloric acid 37 v v SG 1 18 a2 34 OS moLL nitric acid A2 Using a measuring cylinder add 9 of nitric acid 3 2 to a 1 litre volumetric G4 flask containing about 16 of water 3 1 and swirl to mix Allow to cool make to G4 the mark with water 3 1 stopper and mix Transfer to a polythene bottle and store at room temperatures GI 4 QUALITY CONTROL MATERIALS gt may be used to verify that within laboratory R8 repeatability is acceptable A certified reference material may be used from time to time to check for bias e g IBCR143R Sewage
48. ds to apply in practice when measuring or realising a particular experimental value e g mass temperature concentration of a calibration standard etc Degree of control refers in general terms to the uncertainty that is acceptable in the measured experimental value The two examples below illustrate the issues involved a Degree of Control and Instrument Calibration When carrying out an SOP for the determination of the pesticide p p DDE in animal fat or a soil sample by some instrumental technique e g GC MS the analyst will need to choose an appropriate sample of p p DDE for use in the preparation of an instrument calibration solution Two choices might be available e Acommercial grade chemical stated purity gt 95 e A formally certified reference material certified purity 99 6 0 4 The former material would contribute about 5 to the calibration uncertainty whereas the latter will contribute only 0 4 There will be similar uncertainty contributions associated with the result ultimately obtained on the test sample Depending on the purpose of the analysis the analyst makes a choice as to the appropriate calibration material If the analysis is being carried out for the purpose of screening a large number of test samples to evaluate the proportion of samples contaminated with p p DDE an uncertainty contribution of about 5 due to instrument calibration might well be acceptable If however the analysis was being ca
49. e encountered in an SOP e approximate volume measurements where it is reasonable to conclude that a graduated beaker or measuring cylinder would be adequate e g dissolve the residue in about 10mL of hexane e measurements of time where it is reasonable to rely on a clock or stopwatch e g shake the mixture for 60 minutes e measurements of length where it is reasonable to use a ruler e g fused silica crucibles 57 mm diameter e reagents with specified approximate concentrations e g approx 6 mol L e equipment with approximate specifications e g medium grade porosity filter paper e temperatures with approximate specifications e g room temperature red heat Once a particular experimental value has been allocated to the green category the analyst may for all practical purposes regard the realisation of those values as easily achievable using basic knowledge skills and procedures 8 LGC VAM Traceability Guide 2 4 2 Amber Category This represents a significant degree of control such as that provided by properly maintained and calibrated equipment for common measurements such as mass volume temperature instrument response etc All values appearing in the equation used to calculate the final analytical result would either be in the amber category or the red category see next Section The quality assurance QA system of a properly equipped and appointed laboratory will n
50. ecified values e g purity concentration that are used either as standard titrants or for standardising titrants in volumetric procedures Matrix reference materials where the SOP specifies that a reference material must be included with each batch of test samples analysed Physical properties e g molecular masses density values that appear in the equation used to calculate the final analytical result and have to be obtained from tables Individually calibrated items of volumetric glassware where the tolerance of a class A item is too large to be fit for purpose Sample extractants where the composition has a significant effect on the final analytical result e g 0 07 mol L hydrochloric acid used to simulate stomach acid in testing paint on toys for available toxic elements LGC VAM Traceability Guide 3 Identifying the Traceability Requirements for a Standard Operating Procedure An Example The following discussion describes the application of the above approach to a typical SOP the determination of potassium iodide in vitamin tablets The SOP is given in Appendix 2 3 1 Key Steps in the Attainment of Traceability Summarising the discussion of the previous Section the analyst must carry out the following steps in order to obtain valid and traceable results 1 Select a properly validated method with a scope that is applicable to the test sample both in terms of matrix composition and analyte concentration 2
51. ed all reagents must be of analytical reagent quality or better The water must be glass distilled or of at least equivalent purity Acetonitrile HPLC grade A2 2 Dichloromethane A2 A2 A2 A2 A2 A2 3 8 Dimetridazole gt 99 purity available from Sigma Chemicals R6 3 9 Ammonium acetate buffer Dissolve 32g of ammonium acetate 3 4 in of water Adjust the pH to 4 4 to 44 G4 4 5 with glacial acetic acid 3 5 and make up to with water A3 AS 3 10 Di potassium hydrogen orthophosphate trihydrate 0 2 moLlL aqueous solution Dissolve m of di potassium hydrogen orthophosphate 3 7 in water and make up 44 to 5 3 11 Potassium dihydrogen orthophosphate 0 009 mol L aqueous solution Dissolve 1 2248 g of potassium dihydrogen orthophosphate 3 6 in water and make up 44 to 1 litre in a graduated flask A5 Phosphate Buffer Mix equal quantities of 0 2 mol L di potassium hydrogen orthophosphate solution 3 10 with 0 009 mol L potassium dihydrogen orthophosphate 3 11 This will give a buffer solution with a pH of between 8 0 and 8 5 this should be confirmed using a pH meter A3 LGC VAM Traceability Guide 53 5 4 3 13 Mobile Phase of ammonium acetate buffer 3 9 of acetonitrile 3 1 3 14 Dimetridazole stock standard solution Dissolve 100 0 mg of dimetridazole 3 8 in methanol 3 3 in a 100 mL graduated flask Make up to the mark with methanol and mix thoroughly This solu
52. ed in this guide is based on the recently published Eurachem CITAC document Traceability in Chemical Measurement The main aim of the present guide is to provide an interpretation for analysts of the practical requirements associated with the Eurachem CITAC document Hence we have focussed on those essential practical steps involved in a typical analytical procedure for which traceability must be established and explained how the analyst can judge what is required in their particular circumstances In order to simplify this process we have adopted a colour coding system which we hope will help analysts to classify the traceability requirements of their methods in accordance with the impact on the final analytical result of each individual traceable calibration The guidance is illustrated using extensive examples of several analytical methods and standard operating procedures taken from the food and environmental measurement sectors The examples are based on real analytical procedures simplified where necessary to aid clarity We hope they will facilitate an understanding of the principles of traceability and prove useful for both private study and training courses The examples and the procedures described in this guide were presented applied and reviewed at two workshops organised by LGC and involving analysts managers experts on traceability and representatives of accreditation bodies The final version of the guide and examples incorporates m
53. eparated into 2 layers filter the extract through a filter funnel containing a little glass wool and collect the extract in a separating funnel Allow the layers to separate and collect the lower dichloromethane layer Condition a silica cartridge 5 1 by passing of dichloromethane 3 2 through it Then using a pipette add 10 mL of the dichloromethane sample extract to the cartridge When the meniscus has reached the surface of the packing do not let the cartridge go dry wash the cartridge with a further of dichloromethane 3 2 and then dry the cartridge with a gentle stream of air When the cartridge is completely free of dichloromethane elute the compounds from the cartridge with of mobile phase 3 13 Collect the eluate in a 10 mL graduated flask and make up to the mark with mobile phase 3 13 This solution is now ready for examination by HPLC as described in section 7 7 HPLC DETERMINATION 7 1 7 2 XVI System suitability for the screening test Allow the HPLC system to equilibrate by running the mobile phase for at least before any injections are made Inject 100 uL of the calibration standard Ensure that the retention time for dimetridazole is not less than 10 minutes Repeat the injections a further two times The peak heights obtained from the data acquisition system should agree to within 5 of the mean value Calibration Calibrate the HPLC system using the calibration standards prepared in 3 16 Construct
54. eparation e g dissolution digestion extraction or cleanup of the sample according to fixed and defined experimental conditions such as time temperature acid concentration solvent composition etc Measurement of the amount e g volume of the prepared sample extract Calibration of an instrument with a standard solution of known concentration Measurement of the instrument response obtained for the sample extract DEP E CE Calculation of the concentration of analyte in the original sample LGC VAM Traceability Guide 1 Examination of the above shows that a typical analytical procedure requires measurements to be made e g sample mass extract volume etc and fixed experimental conditions to be realised e g time temperature reagent concentration for sample extraction etc The essential task of the analyst is to ensure that all of these experimentally measured or realised values are traceable to reliable measurement standards Ideally the measurement standards selected for the purpose of establishing traceability should be internationally recognised as being fit for that purpose as emphasised in the VIM definition of traceability Property of the result of a measurement or the value of a standard whereby it can be related to stated references usually national or international standards through an unbroken chain of comparisons all having stated uncertainties It will be noted that the VIM definition refers to national
55. es shows that various options are available when selecting a burette for a particular application The table gives three examples Type of Burette Capacity Graduations Cost Class A borosilicate glass BS846 10 mL 0 02 mL 58 Class A borosilicate glass BS846 10 mL 0 05 mL 32 Class B Schellbach glass BS846 10 mL 0 1 mL 19 Any of these burettes will provide the necessary degree of control as they will all enable an expected 10 mL titre to be measured to about 1 or better although the Schellbach glass burette is exactly at this limit The only task for the analyst is to check what 12 LGC VAM Traceability Guide specification of volumetric glassware is provided by the laboratory s QA system If the specification provided by the QA system does not give the necessary degree of control required for a particular SOP the analyst will have to make special arrangements to obtain the necessary stated reference i e it will fall in the red category and not the amber category The stated reference for the molarity of the sodium thiosulphate solution could in principle be provided by a commercially produced volumetric standard solution with a stated molarity value For this purpose the analyst will need to identify a suitable source of the volumetric reagent For example 1 litre of a 0 1 mol L sodium thiosulphate solution with a tolerance factor of 0 001 mol L i e 1 may be purchased from recognised and reputable laboratory reagent supp
56. etric solution It is reasonable for the analyst to presume that such values may be realised in practice with an appropriate degree of control by using chemicals of the prescribed specification that have been obtained from reputable manufacturers Additionally such chemicals should be properly stored once received in the laboratory and assigned an expiry date after which they should not be used For certain reagents it may also be appropriate for the laboratory policy to stipulate say that the last 10 or 5 of reagent remaining in a bottle should not be used but discarded The foregoing approach to sourcing and using common chemical reagents with a commercial specification would normally be documented in a laboratory s QA system Such values are therefore allocated to the amber category Some of the reagents in the above list do not have a stated value attached to them for example bromine is just specified as reagent grade In such cases the analyst will need to judge whether a grade suitable for general laboratory work or analytical work is required In either case the sourcing and use of such chemicals should be covered by the QA system and therefore the corresponding traceability requirements are allocated to the amber category The reagent list also specifies purified water but gives no further details of the required purity level In such circumstances the analyst s experience might suggest that water of a purit
57. fied concentration purity conc nitric acid acetonitrile HPLC grade Also a 930 7911119 but one which requires the analyst to select the gi needed to carry out a particular SOP E g special stated im references needed such as materials with specified values concentration purity used for instrument calibration matrix reference materials used for QC physical properties molecular weights individually calibrated glassware N1 Does not affect the result containers only N2 Specified equipment with no impact on traceability N3 Important with respect to the accuracy of the result but no impact on traceability G1 Approximate temperature do not need specially calibrated thermometer G2 G3 G4 G5 Approximate concentrations prepared from specified reagents G6 outine laboratory equipment No significant effect on final resul G7 Al Purity important but not a calibrant therefore not red category A2 Specified reagents covered by Lab QA procedure A3 Specified equipment covered by Lab procedure LGC VAM Traceability Guide AS A6 A7 8 9 10 11 12 A13 urity reagent used for standardisation reagent with required purity and uncertainty R
58. igh a cleaned labelled silica ashing dish to 0 1 mg le or m fresh sample into the dish If the sample is mostly liquid it must be dried down gradually on a hot plate before transferring to the muffle furnace Samples containing lots of sugar or fat are liable to spit and must be charred over a Bunsen flame or under an infra red lamp before placing in the muffle furnace Transfer approximately 2g of freeze dried samp spread the sample into a thin layer and reweigh to Place into a muffle furnace whilst still cold the sample dishes at least one empty dish to act as a sample blank and the appropriate quality control material s to act as quality control standard s Reset and ensure the programme is as specified in section 5 Press the RUN button to start the programme After at 500 10 C open the furnace door and leave to cool to 200 C according to the digital muffle readout Heating will stop automatically as soon as the door is opened If the ash contains black carbonaceous material allow the dishes to cool to A7 A7 G2 A7 A7 G2 G2 G2 G1 Gl A4 10 A10 A4 G2 A7 A7 GI 7 3 5 7 4 1 7 5 1 1 5 2 temperaturel Add sufficient purified water 3 4 to dampen the ash dry down on a hot plate and place back in the muffle furnace for a further at 7 3 Preparation of solutions Allow the dishes to cool to less than 100 C according to the digital muffle and remove using long tongs 2 4
59. imum sensitivity to noise ratio according to the instrument makers instructions INSTRUMENT CALIBRATION AND SAMPLE ANALYSIS Working standard iron solution Dilute the standard solution 5 1 1 9 with water 4 1 Working standard copper solution Dilute the standard solution 5 2 1 9 with water 4 1 and then dilute the resulting solution 1 9 with water 4 1 Working standard manganese solution 797218 Dilute the standard solution 5 3 1 9 with water 4 1 and then dilute the resulting solution 1 9 with water 4 1 Working standard zinc solution TED Dilute the standard solution 5 4 1 9 with water 4 1 and then dilute the resulting solution 1 9 with water 4 1 Mix by inversion each standard solution in the calibration line and aspirate in turn beginning with the highest concentration standard and working down to lower concentrations Wait for before recording the absorbance reading When all the standard solutions in the range have been run begin aspirating the sample solutions in the same way After every 10 sample solutions aspirate the highest concentration standard in the range and check for instrument drift If the absorbance reading for a sample solution is above the highest concentration standard in the range then dilute the sample with 0 5 mol L hydrochloric acid 4 3 If the reading for a sample solution is lower than that for the lowest standard in the range run the sample solution on a
60. in EB of water 3 2 and add of Triton X 100 10 3 1 CALIBRATION STANDARDS Sodium chloride 99 999 Sigma Aldrich Cat No 20443 9 LGC VAM Traceability Guide All A3 A2 A2 NI NI A3 A2 A2 R5 A2 4 10 G4 G4 R6 XXVII 5 CERTIFIED REFERENCE MATERIALS 5 1 Certified Reference Material NIST 909b R7 R9 6 PRINCIPLES OF OPERATION All stock standards and control material must be prepared according to the relevant procedure prior to analysis Serum test samples are accurately diluted to an intermediate concentration range using the Hamilton Microlab 500 and then again accurately diluted to the optimal concentration range using the Hamilton Microlab 500 All The aqueous diluent contains cesium chloride which acts as an ionic suppresser Diluted efer ENCES samples are then quantitatively analysed by atomic absorption spectrometry in this section Three separate aliquots of each test sample are analysed in triplet defined elsewhere The mean standard deviation and coefficient of variation are reported for tests and control material Control material is run immediately following each batch of samples N B The major source of error for sodium analysis comes from operator contamination wear gloves when handling all material used for this procedure including during labelling of tubes 7 PREPARATION OF SOLUTIONS Thaw three aliquots of each test sample Also allow one set of contr
61. interlaboratory exercise to determine iron in river water at the level of 280 ug L each laboratory sourced its own measurement standard for iron and the between laboratory coefficient of variation of the results was 41 When the traceability of each laboratory s result to a common high quality iron standard was established the coefficient of variation was reduced to 11 Whilst it is generally not practicable to ensure the use of common standards for all of the measurements involved in a chemical analysis steps should be taken by analysts to ensure that the measurement standards they are using are of an appropriate quality This effectively requires the analyst to check that the stated values of the standards have been established by valid procedures and are accompanied by an uncertainty estimate that is appropriate to the particular analyses being carried out This guide provides practical advice and guidance to analysts on how to establish the traceability of their measurements to reliable measurement standards It is based upon the principles described in the Eurachem CITAC document entitled Traceability in Chemical Measurement March 2003 The latter document may be viewed on the Eurachem website www eurachem ul pt 1 2 Traceability in Chemical Measurements A typical chemical analysis usually involves a number of individual operations such as the following 1 Measurement of the amount e g mass of sample taken for analysis 2 Pr
62. is aspect of reliable measurements by the accreditation bodies and others It does appear as well that there is growing recognition of the real benefits of applying the concept of traceability to aspects of chemical measurement beyond the calibration of physical parameters such as mass or volume Recognition of the benefits has lead to a desire to apply traceability fully in the chemical measurement laboratory and this has not always proved to be straightforward A major problem brought to our attention is simply recognising which of the many facets of a measurement need to be traceable Beyond that it is often even more difficult for those inexperienced in the concepts to identify the relative importance of each of the parameters they have identified with respect to establishing traceability of the end result Many analysts also find it difficult to judge how much time and expense is justifiable either for any given parameter or in establishing the traceability of the overall measurement In other words it is not clear how they can apply the same concepts of fitness for purpose that they adopt in developing and validating other aspects of their measurement methods This situation has become clear both from ad hoc comments and also from discussion at a further series of training workshops which we have organised since publication of the second edition These were intended to achieve two main aims Firstly to explain the concepts of traceability and
63. ixture Overlay with an additional 10 g of 44 potassium carbonate and again compact the mixture thoroughly by tapping Ignite the mixture for at 675 to 700 C in a muffle furnace preheated to that G2 412 47 temperature 6 4 Cool add of water or more if necessary heat gently to boiling and decant G4 through a filter 3 2 into a conical flask of suitable size for example 500 mL NI 6 5 Repeat the extraction by boiling with of water then wash the crucible and the G4 char on the filter with hot water until the filtrate measures approximately mm G4 6 6 Add of freshly prepared bromine water 4 3 1 then slowly add of dilute G4 G4 phosphoric acid 4 6 1 and boil until starch iodide paper is no longer coloured blue by the vapours During the boiling add water from time to time as necessary to maintain a volume of at least G4 6 7 Wash down the walls of the flask with water and continue the boiling for BENNE G2 6 8 Cool add of phenol solution 4 2 1 again rinse the walls of the flask and allow G4 to stand for t G2 6 9 Add of dilute phosphoric acid 4 6 1 and of potassium iodide 4 5 1 and G4 G4 titrate immediately with 0 01M sodium thiosulphate 4 9 1 adding thyodene 4 7 as the end point is neared LGC VAM Traceability Guide V 7 VI CALCULATION OF RESULTS Essentially the above procedure is based on the following reaction 6Na 5 03 T B x MxMWrt x 106 xA 6x1000x W Iodide
64. knowledge the analyst with responsibility for applying the SOP should control the acid concentration to 10 0 5 This recommendation is made because the acid concentration in the SOP is specified as 10 v v that is to the nearest whole number which carries the implication that it should lie between 9 5 and 10 5 2 3 3 Uncertainty Data It will be appreciated from preceding discussions that the issue of traceability is closely linked to measurement uncertainty Information on the uncertainty budget for an SOP and the individual sources of uncertainty will therefore be of value when considering the traceability requirements for the SOP Comprehensive guidance on measurement uncertainty has been published by Eurachem and further information may be found in the following document Quantifying Uncertainty in Analytical Measurement 2 edition www eurachem ul pt 2 3 4 Analysts Experience In addition to the above more formal sources of information the analysts general experience will often provide useful guidance as to those parts of an analytical procedure where a greater degree of control is required and those parts where lesser control is acceptable LGC VAM Traceability Guide 7 2 4 Obtaining the Appropriate Degree of Control Once the appropriate degree of control has been identified for a particular step in an SOP consideration must be given as to how this degree of control will be obtained in practice This effectively mea
65. l arrangements The central provision of laboratory services such as demineralised water and piped gases to a particular specification should also be covered by the QA system It is important for the analyst to be aware of exactly what is covered by the laboratory s QA system and that the specifications involved meet the analyst s requirements for a particular SOP If they do not the analyst will have to make special arrangements over and above that provided by the QA system and the amber category Such arrangements will fall into the red category 2 4 3 Red Category This also represents a significant degree of control but one which requires the analyst to select the special stated references needed to carry out a particular SOP It is important to note that these special stated references are not necessarily difficult to obtain nor do they necessarily provide a greater degree of control than those in the amber category However their selection does require the analyst to give some special consideration as to what will be appropriate since it cannot be automatically assumed that the laboratory s QA system will cover the requirements of the SOP Examples of stated references that would be allocated to the red category include the following e Materials with specified values e g purity concentration physical properties that are used for instrument calibration purposes LGC VAM Traceability Guide 9 10 Materials with sp
66. le is shaken with 5 parts by volume of water for 16 hours The sulphate content of the water extract after filtration is determined gravimetrically following precipitation as barium sulphate 3 APPARATUS In addition to normal laboratory equipment the following is required Mechanical shaker capable of keeping 10 g of soil sample in continuous suspension in 50 mL of water Filter papers ashless medium grade porosity 8 Filter papers fine grade porosity 3 un 4 REAGENTS XX The following reagents are required Hydrochloric acid mmu Carefully mix SU of conc hydrochloric acid 4 2 with water 4 1 and dilute to Transfer the solution to a polythene bottle Barium chloride solution 015 Dissolve 100 1g of barium chloride hydrate 4 3 in about GU Me eyes 4 1 Warm the solution on a hot plate to aid dissolution Soa vnl susc dilute to and transfer to a glass or polythene bottle Sodium hydroxide solution Dissolve 20 g of sodium hydroxide pellets 4 4 in 8 of water 4 1 with stirring to aid dissolution Transfer to a glass or polythene bottle Methyl orange indicator solution 3 09 Dissolve 100 mg of methyl orange 4 5 in about 4 1 Warm the solution on a hot plate to aid dissolution EISE and dilute to Transfer to a G6 G6 A8 A2 A2 A2 A2 A2 A2 G7 G4 G4 G
67. liers for about 7 Alternatively and as actually specified in the SOP the molarity value of the sodium thiosulphate solution could be established experimentally by standardisation against potassium iodate For this purpose the analyst will need to understand the principle underlying the standardisation and the way the molarity value is calculated The standardisation is based on the following equivalence 6Na S O The calculation of the molarity is based on the equation below oe MWh x volume of Na S O In terms of establishing traceability the principal task of the analyst is to identify and obtain an appropriate source of potassium iodate as this is now the stated reference on which the molarity of the sodium thiosulphate is based and to which it is traceable The important property of the potassium iodate is its purity and the uncertainty of the purity value Examination of catalogues from various suppliers shows that a number of options are available Type of Potassium Iodate Purity Cost General purpose grade GPR 299 595 15 100 g Analytical grade AR gt 99 9 18 100 g Certified reference material CRM 99 96 0 03 30 50 g The uncertainty degree of control provided by the different potassium iodate materials improves progressively from the general purpose grade chemical through to the certified reference material with a formally certified purity value For the pre
68. lity Guide A5 A5 R9 G2 A9 G4 N3 R6 A6 A6 A5 XXV R7 The result for the QC material should lie within the set limits for the particular QC material concerned XXVI LGC VAM Traceability Guide 7 7 SOP CLIN 2 ANALYSIS OF TOTAL SODIUM FROM SERUM BY 1 2 ATOMIC EMMISSION SPECTROMETRY INTRODUCTION Purpose and scope To enable the analysis of total sodium from serum by atomic emission spectrometry for the generation of reference targeted results Reference values produced will conform with the acceptable analytical criteria of a Reference Method The method is applicable to serum sodium levels in the range 100 to 180 mMol L Responsibility Procedures will only be undertaken by appropriately trained personnel The operator is responsible for preparing the samples standards and QC materials in the prescribed manner and in completing and or collating the required documentation correctly The Reference Laboratory Manager will be responsible for final authorisation of Reference values APPARATUS In addition to normal laboratory apparatus the following is required 2 1 Varian FS220 Atomic Absorption Spectrometer with Varian SPS 5 Autosampler 2 4 Jun Air Compressor 2 9 Rotamixer 2 8 Sarstedt 13 mL polypropylene tubes 2 9 25 mL Universal containers a REAGENTS ies Internal Quality Control Solutions Aqueous Cesium Chloride Diluent Dissolve 12 7 g of cesium chloride 3 4
69. ll have a direct effect on the accuracy of the final analytical result An appropriate degree of control would be provided by using volumetric glassware volumetric flasks pipettes etc These volume measuring devices typically have measurement tolerances of 0 596 This degree of control will be more than adequate for many chemical analyses The anhydrous sodium sulphate is used to dry the extract and therefore the exact mass is not critical to the accuracy of the final result A sufficient degree of control in realising the 2g quantity would be obtained by use of a top pan balance or even by simply filling the column to an appropriate depth The rinsing of the column specifies using about 5 mL of iso octane This volume could be realised with sufficient accuracy by use of a 10 mL measuring cylinder The temperature of the water bath of the rotary evaporator is specified not to exceed 50 C If the water bath is actually operated at a temperature significantly lower than this say 40 C a sufficient degree of control of the bath temperature would be provided by an ordinary laboratory mercury in glass thermometer since any uncertainty in the temperature reading of the thermometer would be expected to be much less than 10 However if it was decided to operate the water bath at 49 C although a mercury in glass thermometer would still be suitable the accuracy of the graduations would require checking against a properly calibrated thermo
70. meter Thus a greater degree of control of the water bath temperature is required when it is close to the specified upper permissible limit 2 3 Choosing the Appropriate Degree of Control When deciding what degree of control is appropriate when a particular value or experimental parameter has to be measured or realised in practice the analyst may find the following sources of guidance helpful 2 3 1 Fitness for Purpose Criteria Whenever an analysis is carried out the analyst should be aware of the ultimate end use to which the results will be put This will determine the uncertainty in the final result that is acceptable and fit for purpose For example if a contaminated land site is being surveyed to assess the distribution pattern of hot spots measurements with an uncertainty of 50 might be acceptable Conversely if a sample of blood is to be analysed to determine whether the ethanol content exceeds that permitted in drink driving legislation a much smaller uncertainty perhaps 5 or less might be required The degree of analytical control that must be applied in these two situations therefore differs markedly Clearly the individual steps in the analytical procedure that make a significant contribution to the overall uncertainty must be controlled to a smaller degree of uncertainty than that required in the final analytical result Ideally experimental values having a significant effect on the final result should be measured or
71. ns identifying appropriate stated references that may be used to realise the experimental values concerned with an appropriate uncertainty Because there are many different degrees of control and various ways to obtain them it 1s helpful to allocate the degree of control required for a particular experimental value to one of three categories This will help the analyst to identify traceability requirements for an SOP in a focused and systematic manner The three categories colour coded green amber and red are discussed in detail below There are also features of an SOP which although important in successfully executing the procedure have no impact on the traceability of the method and consequently do not require categorisation Examples of features which fall into this grey category include tongs desiccators and containers required to hold a volume 2 4 1 Green Category This represents a minimal or basic degree of control in which normal routine laboratory equipment reagents etc are able to provide appropriate stated references This degree of control would be readily obtainable even in a laboratory with a basic level of analytical equipment and would not require the analyst to make any special arrangements It is applicable to those steps in an analytical procedure that do not have a significant effect on the uncertainty of the final analytical result By way of example it would be applicable where the following situations ar
72. of interest Major suppression or enhancement effects are compensated for by use of an internal standard rhodium APPARATUS Perkin Elmer Elan 5000A inductively coupled mass spectrometer operating under the following typical conditions e Note the sample uptake rate affects the sampling position in the plasma 1on intensities and the formation of oxides and doubly charged ions Once set all standards and samples shall be analysed using the same sample uptake rate REAGENTS 5 CALIBRATION STANDARDS 5 1 Certified plasma emission standards nominal 10000 pg mL covering the elements of interest 6 SAMPLE PREPARATION LGC VAM Traceability Guide A7 A7 A7 A7 A7 A2 A2 R6 AI XI If necessary sample extracts must be diluted immediately prior to analysis using 196 v v nitric acid or another acid as appropriate to bring the elemental concentration into the calibration range of the instrument 1 pg mL To achieve this an accurately measured aliquot is diluted to a known volume A suitable internal standard e g rhodium is also added at a concentration of 5 ng mL which is appropriate for most situations 7 VALIDATION OF INSTRUMENT PERFORMANCE The instrument must be set up and its performance validated as described in the manufacturer s user manual 8 INSTRUMENT CALIBRATION 8 1 Multi Element Stock Solutions of the Elements to be Determined A multi element stock solution c
73. ols and one set of G1 standard solutions to reach All samples controls and standards must be allowed to reach prior to Gl dilution Place samples and controls on a roller bed or spiramix for at least prior to G2 dilution to ensure complete mixing Standard stock solutions must be vortex mixed placed on spiramix prior to diluting Standards include an S sample diluent only and an additional S4 required for instrument optimisation prior to sample analysis see 7 1 Label two sets of polypropylene tubes Set one to be used for the intermediate dilution of each thawed test control and standard set two sufficient for the analysis of each test in triplet and controls Label a set of universal containers for the standards 7 1 Preparation of Stock Calibration Standards Standard 0 sample diluent Standard 1 100 0 mMol L Weigh to 4 decimal places 0 5 g of sodium chloride 4 1 into a 4 10 volumetric flask and make up to the mark with de ionised water 3 2 AS Standard 2 120 0 mMol L Weigh to 4 decimal places 0 7g of sodium chloride 4 1 into a A4 A10 volumetric flask and make up to the mark with de ionised water 3 2 AS Standard 3 140 0 mMol L Weigh to 4 decimal places 0 8 g of sodium chloride 4 1 into a Qe A4 A410 volumetric flask and make up to the mark with de ionised water 3 2 AS XXVIII LGC VAM Traceability Guide Standard 4 180 0 mMol L Weigh to 4 decimal places
74. ontaining each of the elements of interest at is prepared in 196 v v nitric acid by volumetric dilution using individual concentrated solutions purchased from a commercial supplier 5 1 8 2 Internal Standard Rhodium Stock Solution A stock solution of rhodium at 10 ug mL in 1 viv nitric acid is prepared by volumetric dilution of the concentrated solution purchased from a commercial supplier 5 2 8 3 Calibration Standards Standard solutions for calibrating the instrument are prepared by volumetric dilution from the multi element stock solution 8 1 in a matrix that matches as closely as possible that of the samples to be analysed At least two calibration solutions are prepared covering the expected concentrations in the samples plus a blank e g ol 100 ng mL The multi element calibration standard solutions must also contain the internal standard 8 2 at a concentration of 8 4 Calibration Procedure Calibration is performed according to the procedures detailed in the instrument user s manual and before any test samples are analysed Where possible at least two isotopes of each element are to be measured The calibration solutions are aspirated into the instrument and between 3 and 5 replicate measurements are obtained per calibration solution A parameter file is created for the elements of interest for the purposes of data acquisition Acquisition is performed in the peak hop mode using one point pe
75. ormally provide the appropriate stated references via a defined policy for ensuring the quality of common measurements For example the regular maintenance and calibration of balances by a service engineer should ensure that measurements of mass are traceable to the national international standard kilogram The purchase of volumetric glassware with a stated specification from a reputable supplier combined with procedures for regular maintenance and checking of the glassware should provide appropriate stated references for volume measurements The availability of a calibrated thermometer for checking the accuracy of working thermometers will provide traceability for temperature measurements A laboratory s QA system should also include a policy for the purchase of common chemical reagents e g conc nitric acid SG 1 42 phenol 80 w w potassium iodate 799 595 acetonitrile HPLC grade from recognised producers and suppliers Where such producers suppliers are certified to ISO9001 the purchasing laboratory has the added assurance that the quality systems used in the production and supply of common laboratory chemicals have been the subject of a third party audit The purchase of laboratory chemicals from a reputable supplier combined with a policy for their storage and setting a shelf life once they are received in the laboratory should ensure that reagents of the specified grade may be realised by the analyst without the need for further specia
76. ovided for the set of SOPs where we noted two problems related to the colour coding system which is a key feature of the guide It was apparent that many users had tried unnecessarily to establish traceability for every artefact used in an analysis including items such as crucibles or tongs and were surprised that we had not included them in our model answers They were frequently confused as to the distinction between such items and those in the green category This represents a minimal or basic degree of control in which normal routine laboratory equipment reagents etc are able to provide appropriate stated references To avoid confusion we have introduced a new grey category for those items which need not be considered for traceability The second problem arises because for any given item in an SOP the category may depend on the circumstances in which it is used As a result we were frequently asked why we had chosen one category whilst the user had quite rightly identified a different category as being more appropriate in their own laboratory This has been addressed by cross referencing every colour coded entry in the answers to a short explanation of why we chose that category We hope you find these improvements to the guide of value and that it is easier to use as an aid to evaluating your own laboratory s methods as well as a basis for training courses Any further comments or suggestions about the guide and its use are welcome
77. ow 14 4 L min A7 Acetylene Flow 2 20 L min A7 Calibration Mode Concentration Measurement Mode PROMT Measurement Time G2 Read Delay 5 05 G2 Minimum Reading Disabled Smoothing 5 point Wavelength 589 nm AII Slit Width 1 0nm A7 Lamp Current N A Lamp Position N A Background Correction Off Concentration Dec Places 4 Burner Height 2 75 mm A7 Probe Height 0 mm A7 Rinse Rate 1 Rinse Time G2 DATA ANALYSIS The FS 220 plots its own calibration curve as described in the FS 220 operating procedure The resulting data are transferred to a Microsoft Excel spreadsheet and the mean standard deviation and coefficient of variation are calculated for the test and control samples If the control values fall within the following acceptable limits the data can be reported Results are reported to 3 decimal places units are mMol L Assay acceptance limits The long term precision is typically 1 Bias is checked using NIST SRM909b and should not exceed 0 5 Sodium Certified Value Level 1 mMol L WOM R9I R7 Sodium Certified Value Level 2 mMol L KIKU R9I R7 Check the current SRM target values for this QC preparation The current certificate can be obtained from the Internet www nist gov srm Calculation of Results The concentration of sodium in the original serum sample is calculated from the following equation Na serum T 1 x D where Na serum concentration of sodium in serum polynomial fit to the calibration curve from instrument R10
78. owed by thorough rising with purified water 3 REAGENTS Introductory comments For preparation of the reagents and analytical solutions use water free from the cations to be determined obtained either by double distilling water in a borosilicate glass or quartz still or by double treatment on iron exchange resin The reagents must be of at least analytical grade Freedom from the element to be determined must be checked in a blank experiment If necessary the reagents must be LGC VAM Traceability Guide A3 G6 G6 G6 A5 A5 XXXI further purified In determining trace elements it is important to be alert to the risks of contamination particularly by zinc copper and iron For this reason the equipment used in preparing the samples must be free of these metals To reduce the general risk of contamination work in a dust free atmosphere with scrupulously clean equipment and carefully washed glassware The determination of zinc is particularly sensitive to many types of contamination e g from glassware reagents dust etc Hydrochloric acid 6 mol L ydrochloric acid 0 5 mol L Nitric acid 5 v v aq prepared by diluting 4 3 with 4 1 and stored in a plastic vessel 4 7 4 8 Lanthanum chloride solution prepared as follows dissolve 12g of lanthanum oxide 4 7 m of water add of 6 N hydrochloric acid 4 4 and make up to with water 4 1 using a volumetric flask 4 QUALITY
79. r peak The blank solution is also measured and blank readings are subtracted from all subsequent measurements of standards A calibration line is constructed that is linear thru zero 9 SAMPLE ANALYSIS The test samples are analysed in the same manner as the calibration solutions using the same parameter file for the acquisition of data A wash step using nitric acid is included between each sample and standard of at least at uptake rate Some elements are prone to memory effects in the sample introduction system and A2 A5 R6 A2 AS A2 AS R6 A5 G5 G2 G7 XII LGC VAM Traceability Guide may require the wash time to be and a subsequent blank analysis to check such G7 effects have been eliminated One calibration standard is analysed every sixth sample to check for instrument drift If significant drift is observed the instrument is re calibrated and all samples since the last check standard are compensated for the observed drift or re analysed Drift is deemed significant at twice the quoted precision of the measurements 10 CALCULATION AND REPORTING RESULTS The instrument software automatically calculates the concentration of the elements present in the aqueous sample extract Csample by comparison to the relevant calibration data The software uses an equation of the following type R sample R ISin calib C sample x x xF R calib R ISin sample concentr
80. realised with an uncertainty that 1s one fifth or less of the overall target uncertainty for the final result When this condition is met the individual step concerned will make a negligible contribution to the overall uncertainty 6 LGC VAM Traceability Guide 2 3 2 Method Validation Data It has already been emphasised Section 2 1 that the use of a properly validated method operated within its scope 1s essential if reliable results are to be obtained Information from the method validation studies will often assist in identifying the degree of control that 1s required for particular steps in the SOP For example information may be available on the effect that variations in extraction conditions e g time temperature extractant composition have on the final analytical result If changing the extraction temperature by 5 C has no significant effect on the final analytical result then it will be adequate to control the extraction temperature to 5 C This could be achieved using an ordinary laboratory mercury in glass thermometer If changing the extractant composition from say a specified value of 1096 v v nitric acid to 1596 v v has a significant effect on the final result then the acid concentration would have to be controlled to better than 10 5 How much closer the control would have to be depends upon the magnitude of the variation of the final result with variations in acid concentration In the immediate absence of such
81. ric flask and made up to the mark with 0 5 mol L hydrochloric acid 4 5 For the determination of iron manganese and zinc pipette an aliquot portion of the solution prepared above into a 100 mL volumetric flask add of lanthanum chloride solution 4 7 and make up to the mark with 0 5 mol L hydrochloric acid 4 5 CALCULATION OF RESULTS Method of Calculation and Formula The ash content of the sample expressed as a percentage by mass is equal to M Mo x100 Mi Mo where Mo mass g of the empty crucible M mass g of crucible containing the test sample mass g of crucible and residue after ashing Repeatability The difference between the results of two determinations carried out in rapid succession by the same analyst should not be greater than 0 1 g of ash per 100 g of sample LGC VAM Traceability Guide A12 A7 G2 G1 A4 G4 G4 G4 GI G4 G4 A4 A4 A4 XXXIII 7 9 SOP INS 2 DETERMINATION OF THE TRACE ELEMENTS IRON COPPER MANGANESE AND ZINC IN SOLUTION BY ATOMIC ABSORPTION SPECTROSCOPY PURPOSE AND SCOPE The method is for the determination of the trace elements iron copper manganese and zinc in feeding stuffs by atomic absorption spectroscopy The lower limits of determination in the sample based on the preparation by an ashing technique SOP FDS 4 are Iron Fe 20 mg kg Copper Cu 10 mg kg Manganese Mn 20 mg kg Zinc Zn 20 mg kg
82. rried out to check whether a specific test sample complied with a legislative limit and it was suspected that the sample value was close to the limit the smaller uncertainty provided by the certified calibration material would be required Thus the degree of control that is exercised in the calibration of the instrument depends on the ultimate purpose of the analysis there is no one single degree of control that is applicable to all instrument calibration procedures b Degree of Control and Sample Preparation The following is a typical set of operations that might be involved in the preparation of a sample extract prior to measurement by some classical or instrumental technique muss make the sample extract to 50 mL take a 10 mL aliquot and pass it through a column containing approx 2 g granular anhydrous sodium sulphate Collect the eluate in a rotary evaporator flask and rinse the column with about 5 mL of iso octane collecting the rinsings in the flask Evaporate the extract to dryness at a temperature not exceeding The analyst must review this aspect of the SOP in terms of the degree of control that should be applied when each of the values and quantities specified are measured or realised in practice LGC VAM Traceability Guide 5 When making the sample extract to 50 mL and subsequently taking a 10 mL aliquot a significant degree of control must be exercised in the measurement of these volumes since the actual volumes concerned wi
83. rucible appears black carbon return it to the furnace and ash again at 450 to 475 C This ashing which only requires about three to five hours is complete when the ash appears white or nearly white Using tongs transfer the crucible to a desiccator Allow to cool to and weigh M2 to PREPARATION SOLUTION FOR ANALYSIS Wash the crucible out with a total of about of hydrochloric acid 4 2 and add the latter slowly and carefully to a beaker there may be a vigorous reaction due to CO formation Add hydrochloric acid 4 2 dropwise with agitation until all effervescence has stopped Evaporate to dryness occasionally stirring with a glass rod Add of 6 mol L hydrochloric acid 4 4 to the residue followed by about of water Stir with the glass rod which should be left in the beaker and cover the beaker with a watchglass Bring gently to the boil and until no more ash can be seen to dissolve 8 5 Filter on ash free filter paper and collect the filtrate in a 250 mL volumetric flask Wash the beaker and filter with of hot 6 mol L hydrochloric acid 4 4 and twice with boiling water Fill the volumetric flask up to the mark with water final HCl concentration about 0 5 mol L For the determination of copper the solution prepared above can normally be used directly If necessary to bring its concentration within the range of the calibration solutions an aliquot portion may be pipetted into a 100 mL volumet
84. s omitted 9 INSTRUMENT SET UP Measure the atomic absorption of the calibration solutions and of the solution to be analysed using an oxidising air acetylene flame at the following wavelengths Fe 248 3 nm All Cu 324 8 nm All Mn 279 5 nm All Zn 213 8 nm 9 1 Switch on power to the instrument and turn on the fume extraction fan Ensure that the 100mm multi slot burner is securely in place and that it is clean 9 2 Select and fit the appropriate hollow cathode lamp 3 3 Adjust the current of the lamp to the appropriate value Select the required slit width Lamp current Wavelength PM voltage Slit width mA nm Copper 5 324 7 530 0 32 A7 Iron 10 2483 620 0 16 A7 Manganese 5 279 5 530 0 32 A7 Zinc 5 213 0 530 0 32 A7 9 3 Select the appropriate range control UV or VIS and allow 15 minutes for the lamp to G2 stabilise before adjusting the wavelength control to the correct value 9 4 Turn on the air and acetylene and ignite Allow the burner to stabilise for G2 For the IL 453 spectrophotometer the optimal conditions for fuel and oxidant are 4 8 and A9 XXXVI LGC VAM Traceability Guide 9 5 9 6 10 10 1 10 3 10 5 10 6 10 7 11 4 5 L minute respectively and the burner height must be 30 mm Aspirate the highest concentration standard of the range and the one that is designated for instrument set up The take up rate is Adjust the instrument conditions tuning each emission source to give max
85. sent example any of these materials could be used to standardise the sodium thiosulphate since even the GPR material would contribute lt 1 to the uncertainty of the experimentally determined molarity of the sodium thiosulphate solution However in view of the small cost difference selection of the AR grade chemical might be considered the preferred choice LGC VAM Traceability Guide 13 14 The CRM issued by the National Institute of Technology and Evaluation Japan has been certified in accordance with international guidelines e g ISO Guide 35 Certification of reference materials general and statistical principles Consequently this material would provide traceability to a value established by internationally recognised procedures which additionally has full documentation and a stated uncertainty In certain critical applications e g where an analysis may be part of a legal dispute the use of a formally certified material might be preferable since there is less scope for criticism of a result on the grounds that an inappropriate standard has been used Finally if the cost of using the CRM on a frequent basis is considered prohibitive an option may be to use the CRM occasionally to verify the purity of a large batch of the AR grade material The latter may then be used on a daily basis for the routine analysis purposes The above considerations show that the analyst must give some special thought to identifying an appropri
86. sing experimentally specified temperatures It would then be allocated to the red category The addition of 20 mL of water to the residue from the ignition stage when reviewed in the context of the entire method is seen to require only a basic degree of control The 20 mL could be reasonably dispensed using a measuring cylinder or even a graduated beaker The degree of control required of this experimental value is therefore allocated to the green category Equipment and Reagents with Specified Values with no impact on the Traceability Sections 4 5 1 and 6 4 of the example in Appendix 2 refer to containers with specified volumes These volumes do not affect the result but are included to assist the analyst in procuring equipment large enough to contain the amount of material being handled As discussed in section 2 4 these are features of the SOP which although important in successfully executing the procedure have no impact on the traceability of the method and consequently do not require categorisation These are assigned to the grey category Step 6 Traceability Statement The outcome of the above evaluation of the traceability requirements for the SOP for determining potassium iodide in vitamin tablets is summarised by the colour coding of the relevant text as given in Appendix 2 Having completed the traceability evaluation the analyst must then include a traceability statement for those stated references assigned to the red categor
87. software D dilution factor 2025 A3 LGC VAM Traceability Guide 7 8 SOP FDS 4 DETERMINATION OF ASH IN ORGANIC MATTER AND THE PREPARATION OF AQUEOUS SOLUTIONS FOR QUANTITATIVE ANALYSIS PURPOSE AND SCOPE The method is applicable to foodstuffs and biological materials that can be ashed in a muffle furnace at 475 C to produce a white or grey white ash It does not apply to feeding stuffs with high levels of vegetable silica The method is applicable to a range of elements but has been validated for iron copper manganese and zinc PRINCIPLE A representative portion of the sample is ignited under controlled conditions and allowed to incinerate The residue resulting from ashing is treated with hydrochloric acid and solutions prepared for subsequent analysis The elements iron copper manganese and zinc are determined after appropriate dilution by atomic absorption spectrometry APPARATUS In addition to normal laboratory apparatus the following is required 32 Platinum or quartz crucible 33 3 4 Desiccator containing an effective desiccant 3 5 3 6 Watch glass petri dish or similar 3 7 Tongs heat resistant 3 8 Temperature controlled hot plate 3 9 3 10 Glassware must be of resistant borosilicate type and it is recommended to use apparatus which is reserved exclusively for trace element determination All glassware and plastic vessels should be cleaned before use by rinsing with 5 nitric acid 4 6 foll
88. ssel with 0 3 0 5 mol L nitric acid 3 4 and filter the rinsing through the same filter paper into the conical flask 7 10 Quantitatively transfer the combined filtrate and rinsings to a 100 mL volumetric flask Rinse the Buchner flask with of 0 5 moL L nitric acid 3 4 and add the rinsing to the volumetric flask Make up to the mark with 0 5 mol L nitric acid 3 4 Stopper the flask and mix ANALYSIS OF THE EXTRACT Determine the metal concentration in the prepared extract 7 12 using inductively coupled plasma mass spectrometry SOP INS 1 CALCULATION OF RESULT The concentration C in mg kg of the element in the soil is calculated using the following equation v C C mg kg W RTT Cex element concentration ug L in the extract determined by ICP MS The result obtained for the QC sample is plotted on the QC chart The result should lie within the control limits If it does not the matter should be investigated and if necessary the analyses on the test samples repeated LGC VAM Traceability Guide A4 G4 AS G4 G4 GI G4 G2 G7 G4 G4 A5 G4 RIO AS A4 XIX 7 5 SOP ENV 3 DETERMINATION OF WATER SOLUBLE SULPHATE IN SOIL 1 SCOPE The method is applicable to the determination of the concentration of water soluble sulphate in soils and soil like matrices at concentrations in the range 50 to 25000 mg kg 2 PRINCIPLE 1 part by mass of the soil samp
89. tain physical constants may be combined into a single numerical value Equation 3 is an example of this in which the unit LGC VAM Traceability Guide 15 3 2 3 16 conversion factors 10 and 10 the volumetric equivalence factor 6 and the molecular weight value for KI 166 002 of equation 1 have been combined to give a single numerical factor 27667 Iodide Content as KI g tablet SECO eq 3 When an equation of this type is encountered the analyst must identify all of individual component parts making up the numerical factor in this case MW x10 6x10 The traceability and corresponding degree of control requirements for each component may then be properly considered 27667 SOPs may be encountered that do not present an equation in any form Instead they may simply include a statement to the effect that the calculations are carried out using software and a data processing system In such instances the analyst must establish the exact form of the equation that has been programmed into the data system and use this to assess the traceability requirements Finally if the data processing software performs additional data manipulations to those involving the equation the analyst must take due account of this For example if the software also carries out automatic corrections for interferences or non linear calibration plots the validity of these procedures must be established as part of the requirement to
90. tassium iodate that could be used to provide traceability for results obtained using this SOP 3 2 4 Step 5 Identify the Fixed Experimental Conditions used in the SOP 18 Section 5 of the SOP refers to fixed experimental conditions at various stages of the sample preparation procedure for example e Add 7 g of potassium carbonate ignite the mixture for 25 minutes in a muffle furnace at 675 C to 700 C e Cool add 20 mL of water The analyst must obtain or realise values such as these experimentally with an appropriate degree of control The sample preparation requires 7 g of potassium carbonate to be mixed with the ground tablet sample Reviewing this step in the context of the entire method shows that the value of 7 g does not contribute significantly to the final analytical result As the SOP does not specify a tolerance for the specified 7 g a reasonable assumption on the part of the analyst is that it could be controlled to an appropriate degree by weighing on a top pan balance to 1 decimal place The calibration of the balance used is expected to be covered by the laboratory s QA system therefore the required degree of control for the 7 g measurement is allocated to the amber category The practical realisation of a time of 25 minutes is a very simple task Almost any clock or watch will provide the necessary degree of control time intervals easily being measured to within 1 minute The required degree of control is
91. the sulphate content Determination of Sulphate in the Extract Accurately transfer a measured volume V4 of the extract using a pipette to a 250mL beaker The volume V4 of the extract taken for analysis shall be between 10mL and 50mL and shall not contain more than 50 mg of sulphate ions A preliminary analysis may be required to establish the appropriate volume required Add of methyl orange indicator 4 10 to the solution and neutralise pinke orange yellow the test portion with dilute hydrochloric acid 4 7 or sodium hydroxide 4 9 according to the initial pH Add 18 dilute hydrochloric acid 4 7 and if necessary add water to bring the total volume to Zteswi e Boil the solution on a hot plate for at TEE If the solution is clear after boiling proceed to step 6 3 8 If insoluble matter is present filter the hot mixture through a filter paper LGC VAM Traceability Guide GI G7 4 G4 G4 R8 R9 Al2 A4 G4 G2 A5 A5 NI A5 G7 G4 G4 G2 G6 XXI 6 3 9 6 3 10 6 3 11 6 3 12 6 3 13 6 3 14 6 3 15 XXII 3 3 and wash the paper with a small quantity of hot water 4 1 combining the washings with the filtrate Transfer the solution quantitatively to a 500 mL beaker and boil the solution on a hot plate slowly add using a pipette 359 of hot 2008 barium chloride solution 4 8 Heat the solution for and then allow to cool and stand NEUEN
92. tion can be kept for up to 1 month if stored in an amber container and refrigerated at END 3 15 Intermediate Standard 50 ug mLJ Pipette 2 5 mL of the stock standard solution 3 14 into a 50 mL graduated flask Make up to the mark with mobile phase 3 13 and mix thoroughly This solution can be kept for up to 1 week if stored in an amber container and refrigerated at Calibration Standards Prepare standards at by diluting the intermediate standard solution 3 15 with mobile phase 3 13 These must be prepared fresh daily 3 17 Spiking Standard Solution of the standard Pipette 5 mL of the stock standard 3 14 into a 25 mL graduated flask make up to the mark with methanol and mix thoroughly This solution can be kept for up to 1 week if stored in an amber container and refrigerated at QUALITY CONTROL MATERIAL A 10g is spiked with 200 uL of the spiking standard 3 17 to give a QC material with a dimetridazole concentration of 4 mg kg APPARATUS In addition to normal laboratory apparatus the following is required 5 1 Soe utes Whatman Part No WAT051900 5 2 HPLC system consisting of the following items Data acquisition system HPLC Column pH Meter The pH meter should be BET JST GNU and used according to the manufacturers instructions LGC VAM Traceability Guide G4 G4 R6 A4 12 R6 A5 12 R6
93. ty Guide 21 Bibliography Traceability in Chemical Measurement A guide to achieving comparable results in chemical measurements www eurachem ul pt The Fitness for Purpose of Analytical Methods A Laboratory Guide to Method Validation and Related Topics www eurachem ul pt uantifving Uncertainty in Analytical Measurement 2 edition www eurachem ul pt IVINS 22 LGC VAM Traceability Guide 5 Appendix 1 Rationale for traceability category assignment Grey Category Control unnecessary e g tongs desiccators or no traceability issue 1 e parameter does not influence the result However in some cases any deviation from a stated equipment which has no influence on the traceability would be a change in the method e g platinum or quartz crucibles Green category A Win in which normal wein reagents etc are able to provide appropriate stated references E g approximate measurements specifications such as volume beaker measuring cylinder time wall clock length ruler concentration approx 6M HCI temperature room temperature A such as that for common measurements such as mass volume instrument response etc The QA system of a properly equipped and appointed laboratory will normally provide the appropriate stated references E g properly maintained and calibrated equipment such as volumetric flasks analytical balances common chemical reagents of speci
94. uble matter removed by filtration The copper is then deposited by addition of zinc metal filtered off and dissolved in nitric acid The copper content is determined electrolytically 3 REAGENTS During the analysis use only reagents of recognised analytical grade or better 4 Hydrochloric Acid 1 9 Add hydrochloric acid 3 3 to 18 water 3 1 Vs Du Nitric Acid 1 1 Add of nitric acid 3 6 to of water 3 1 Dissolve of potassium permanganate 3 9 in of hot water Dilute to with water 3 1 Sodium Chloride Solution 0 05 w v Dissolve 8 sodium chloride 3 11 in of water 3 1 DES Sulphuric Acid 1 1 Add of sulphuric acid 3 14 cautiously to of water 3 1 Cool LGC VAM Traceability Guide A2 A2 A2 G5 G4 G4 A2 A2 G5 G4 G4 A2 A2 G5 G5 A2 G5 G3 G4 A2 A2 G5 G4 G4 A2 XXXIX Un QUALITY CONTROL A suitable quality control standard should be included with every batch of analysis This should be a recognised international reference material however if such materials are unavailable a suitable blended synthetic standard should be used If this is not possible for certain materials then the control of quality will be demonstrated by other technical data APPARATUS In additional to normal laboratory glassware and equipment the following is required 5 Laboratory Hotplate XL A laboratory oven capable of maintaining a temperature of 105 2 C
95. ume volume temperature temperature time absorbance wavelength pH particle size particle size atomic and molecular weights density etc instrument calibration response factors molarity of volumetric reagents instrument calibration response factors molarity of volumetric reagents composition of reagents used for sample digestion extraction At the analyst s discretion see Section 2 2 2 The chosen stated reference may be a formally certified artefact item of equipment or chemical material issued by a calibration laboratory or a reference material producer and accompanied by a certificate However this is not an automatic and mandatory requirement for a stated reference For example for certain applications volumetric glassware of stated tolerance but without a certificate of calibration may be appropriate for volume measurements Likewise a reagent grade chemical of stated but not formally certified purity may be appropriate for the preparation of an instrument calibration standard It is the analyst s responsibility to decide what stated references are appropriate for a particular analytical determination such that the final results obtained and reported on the test samples are fit for their intended purpose 4 LGC VAM Traceability Guide 2 2 2 What is Appropriate The stated reference that is appropriate for a given application in a given SOP depends on the degree of control that the analyst nee
96. val of undissolved material amp sample impurities Dilute to with water 3 1 and add approximately of sulphuric acid 3 14 to precipitate any lead present Note If the sample contains more than 0 5 lead add of sulphuric acid 3 14 Boil and whilst boiling add hydrochloric acid 3 4 until any silver has been precipitated Remove from the hotplate and filter through an 11 cm Whatman No 541 filter paper 5 9 or equivalent into a 400 mL tall form beaker If a very heavy precipitate 1s present filter as described using a Whatman No 540 filter paper 5 8 or equivalent Wash the contents of the beaker into the filter paper and wash the filter paper at least 3 times with hot water Place the filter paper in the original 400 mL squat form beaker and retain Deposition by Electrolysis of Copper To the filtrate add approximately of zinc metal pellets 3 16 and allow to stand for or until all copper has deposited Filter through a 12 5 cm Whatman No 541 filter paper 5 10 or equivalent into a 1 litre volumetric flask 5 7 Wash the copper into the filter paper and wash the filter paper twice with water 3 1 Retain the 1 litre volumetric flask Open the filter paper 7 5 2 and wash the copper deposit into the beaker with water Place the filter paper with the paper from the first filtration into the original 400mL squat form beaker retained in step 7 4 4 Retain the filter paper Add a few anti
97. y which may be written into the SOP or the Validation Report This statement should indicate the principles and procedures on which the property values are based and identify where traceability can be related to stated references e g calibrated volumetric glassware calibrated weights and balances and where traceability is achieved through the use of certified reference materials In the latter case details of the material must be given which itself must contain a traceability statement Documentary evidence of the traceability chain should be kept and made available to customers on request A suitable traceability statement for those values identified as requiring the highest degree of control i e assigned to the red category in determining potassium iodide in vitamin tablets would be An evaluation of the traceability requirements for the method for determining potassium iodide in vitamin tablets identified four property values requiring a high degree of control Traceability of these values has been achieved as follows e potassium iodate e supplied by XXXXX product code YYYYY with a purity of 77 7 e molarity of standardised sodium thiosulphate e standardised using potassium iodate and calibrated volumetric glassware e vitamin tablet sample weight e all weighings carried out on calibrated balances traceable to national standards e molecular weights of potassium iodate and potassium iodide LGC VAM Traceability Guide 19 20
98. y typically provided by a properly functioning de ionisation system would be appropriate The supply of demineralised water to a specification appropriate for typical analytical work would be expected to be covered by the laboratory s QA system It would therefore be allocated to the amber category If a particular analysis posed special water purity requirements over and above that appropriate for more routine analytical work the analyst would need to address these requirements The traceability requirements for the purity specification would then be allocated to the red category Examination of the SOP as discussed in step 3 Section 3 2 2 shows that potassium iodate is used to standardise the sodium thiosulphate solution the latter being used to determine the KI content of the tablet samples Therefore sodium thiosulphate solution with the specified value 0 1M controlled to a sufficient degree may be obtained from a reputable supplier of such reagents It therefore falls into the amber category LGC VAM Traceability Guide 17 The potassium iodate is simply specified as reagent grade However in view of its function as the essential measurement standard in the SOP to which the final analytical result is ultimately traceable the analyst must consider its traceability and degree of control requirements It is therefore allocated to the red category See Section 3 2 2 for more discussion regarding the choice of the particular grade of po

2. Practical Attainment of Traceability

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