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Contents
1. Figure 26 GUI for the automated spectrophotometry measurement Figure 27 shows the GUI for the photometric mode Above the graph output is the array function where user is need to enter the values of absorbance that they ve obtained and also the value of concentration that they ve fixed earlier For each concentration absorbance reading is taken and keyed in the space given Both value of absorbance and concentrations need to be placed in parallel for the box given 31 Figure 27 GUI for the photometric mode In this GUI also will have the indicator for slope of the graph which user didn t have to calculate as the system can do the operation by itself Besides that the GUI will also display the interception point of a linear graph which will in the end user can obtain the graph equation automatically However Figure 28 shows the GUI for the spectrum mode where graph plotted in this mode will be in spectrum wave In this GUI there are few features firstly is enter the absorbance value obtained In the GUI the box is placed on the left This is the array function calling on user to key in the absorbance value obtained from a fixed wavelength On the right side of the GUI is the box for plotting the spectrum graph It is the graph of absorbance versus the wavelength There are several modes which user can use such as line fixing and dotted value 32 Figure 28 GUI for the spectrum mode The spectrum mode allows sam2. 3v is considered a transition region for which a signal state is not assigned 22 Yotage oo SPACE PAE Logi 0 Transtian Region Tre Legic 1 2 Sy Figure 16 Logic state of data from RS232 There are two types of cable or connector for RS232 which is the DB 9 DTE and 25 pin DTE Figure 17 below show the DB 9 DTE figure of RS232 Data carrier detect Data set ready Receive data Request to send Transmit data Llear to send Data terminal ready Ring indicator Signal ground Protective ground Figure 17Pin out DB 9 DTE Next figure shows the 25 pin DTE Compared to DB 9 DTE it has 25 pins Protective ground Transmit data 2 Transmit data Clear to send Data set ready Request to send 2 Signal ground Data terminal read Data carrier dete Signal quality detector Test pin Ring indicator Test pin Data signal rate detector Transmitter clock DTE Data carrier detect 2 Clear to send 2 Figure 18 Pin out 25 pin DTE 23 24 3 6 Flow chart of the automated spectrophotometry measurement Sample input Tartrazine Early wavelength is set to 300nm Wavelength Display absorption Count wavelength 20 Wavelength 700 Figure 19 Flow chart for automated measurement system CHAPTER 4 RESULT AND DISCUSSION In this chapter the result of the project is presented Calculation graphs block diagram program and GUI will also be presented Firstly the res
3. 2 2 Transmissivity Curve Determination of Transparent Materials Execute repeatedly the point to point operation of steps 1 8 in 5 2 1 with fixed interval within the required wavelength range and mark the transmittance of each point in coordination with corresponding wavelength on the graph paper to prepare the transmittance curve of the material 5 2 3 Absorbance Determination of Transparent Solutions 5 1 4 4 Setscaleas Absorbance 5 1 6 Put sample in light path 5 1 5 Read outdata 5 2 4 Quantitative Determination of Materials by Standard Curve Method Take standard sample with known contents CO 2 Prepare sample and background solution according to related analysis protocol Set wavelength place blank adj zero set scale as steps 1 6 in absorbance and read out the sample 5 2 3 absorbante Repeat above steps to read out absorbances of steps 2 6 in each standard solution 5 2 3 5 Plot on graph paper with known contents and absorbance readings in each sample and draw out related best fitting curve Read out absorbance of unknown sample and find Step 3 in out corresponding conc in curve on the graph paper 5 2 4 5 2 5 Direct Use of Concentration Factor Function After execution the 3 step in the above section figures appeared in the display window is the concentration factor of this standard sample if the scale is setat concentration factor and record this factor This facto
4. 3 Unscrew two M4 screws at the front of instrument base Turn up the upper cover to inspect each part of instrument Please take care not to touch the high voltage assembly situated at the left rear of instrument base if the inspector is carrying electricity 6 1 3 Light Source Replacement Pre adjusted long life precisely assembled light source is installed in this instrument Please observe the following procedure when the damaged light source should be replaced 6 1 3 1 Open the upper cover refer to the illustration in 6 1 2 6 1 3 2 Dismount the old light source assembly Take off the light source connecting cord and unscrew two M3x10 screws Remove carefully the light source 6 1 3 3 Install the new light source in accordance with the reverse order of 6 1 3 2 Connecting order of the light source wires is blue red blue 6 1 3 4 Turn on the instrument power switch and take off a black round cover on the monochromator Turn the wavelength to 550nm to check the light source lamp if it is aligned to the center of the slit 6 2 Instrument Functions Checking Following items can be used for inspection and calibration to confirm that the main unit of instrument had already reached the pre determined standards after ex factory inspection and troubleshooting 6 2 1 Wavelength Checking 52 6 2 1 1 Start up as regular the main unit of instrument and preheat for 30 minutes set the mode as transmittance 6 2 1 2 Turn the w
5. at the correct position Please push the rod lightly when the rod is situated at the correct position in order to ensure the exact position 5 1 6 Changing of scale There are 4 kinds of scales in the instrument Transmittance For transmittance determination of transparent liquid and solid Absorbance For quantitative analysis using standard curve method or absolute absorption method This system can also be used in the dynamic testing Concentration factor For concentration factor setting in the direct read out by the method of concentration factor Concentration direct read out Used for direct read out the concentration in the standard sample method This scale is used for setting and read out and also used for concentration direct read out after the concentration factor had been set Use button to convert the scale and the status of scales are separately indicated by transmittance absorbance concentration factor and concentration direct read out indicating lamps The initial status after start up the instrument is transmittance The sequence is cycled by one step after each pushing 47 5 1 7 RS232C Serial Data Transmission A RS 232C serial communication port is attached in the instrument It can be used for connection with serial printer or with personal computer The RS232C output port definition and data format of this instrument is as follows The data format is Baud rate 9600bps Data bit
6. if structure but more than 2 alternatives are possible In this project we will be using the while loop function as in Figure 14 It also have a stop function as controller for user stop Figure 14 While loop function 3 4 The experiment on Tartrazine concentration Graph for Tartrazine will be created as reference This can aid in the identification of concentration for some unknown sample of solution by measure it 20 from reference graph To record the absorption of Tartrazine this project uses the sample with concentration of 4 5 However it is needed to dilute the sample from 0 045 to 0 0045 so that the absorption does not exceed 2 0 Figure 15 Sample of Tartrazine in different concentration As the spectrophotometer warming up for 15 minutes the dilute solution is put in the cuvette in order to measure the absorption value After that the cuvette closed into the spectrophotometer During the experiment it 1s a must to make sure that the light passes through the optical window and not the sides of the cuvette intended for our finger to control Wavelength for all the sample is all fixed at different concentration of Tartrazine Using spectrophotometer it is necessary to establish a known series of dilution containing known quantities of a solute One of these will contain no solute and is known as the blank water It is used to adjust the instrument to read 100 transmittance or 0 absorbance value The bl
7. intensity of the light and the signal is being amplified and 17 displayed on the monitor Usually an auto zero is made with a blank sample before measurements to get the sample intensity to be measured in reference to the blank That makes it possible to measure only the absorbance of the hydrogen peroxide by first doing an auto zero on a pure sample of the buffer that it 1s diluted in Adjustable aperture Light sensor Output Light source Monochromator Cuvette Figure 11 Structure of the single beam spectrophotometer 3 3 Programming Language For this project the software that going to be developedto communicate between 752s and PC is the LabVIEW The program should control the sample holder s position be able to set the parameters of the UV 752s and retrieve the data via data acquisition LabVIEW is the most adapted software to this kind of case the language which is a graphical programming language Graphical programming language is the language that programmer use to construct the program by manipulating graphical components rather than specifying everything in text Generally it is the most basic in the idea of creating boxes wires and arrows Boxes are like functions in a normal programming language but the different is that it is connected with wires and arrows that represent the relation between the functions 18 From the wires the boxes will indicate the input and output parameters to be measured
8. needed for customizing software for a preferred measurement to suit what measurement parameters the users need The process of software interfacing for the measurement instrument via the PC is called a Virtual Instrument A Virtual Instrument is created to extend the functionality of the measurement equipment By programming any possibilities can be achieved the possibility of allowing measurements that could not be obtained before To develop in creating these Virtual Instrument measurements there are many graphical programming packages for example is the LabVIEW which has been chosen to be used in this project Spectrophotometry is the analysis technique using the electromagnetic spectrum The instrument that is used for this spectrophotometry analysis is the spectrophotometer A spectrophotometer is employed to measure the amount of light that a sample absorbs The instrument operates by passing a beam of light through a sample to measure the intensity of light which reach its detector Tartrazine is used in this project Tartrazine or known as the E102 or even FD amp C Yellow 5 us a synthetic lemon yellow azo dye used as food colouring It is water soluble and has maximum light absorbance in an aqueous solution at 427 2 nm 1 2 Problem Statement Most of spectrophotometry experiment that being done take a longer time to complete by students By implementing this LabVIEW software to have a proper GUI for them could be useful as their
9. of the light shuttle 3 Re position the rack 4 Receiver is damaged and need be replaced or not connect the plug or connection is poor 1 Correctly select the gain or check the light from the lamp to see if it is not entering into the slit adequately elevate the lamp voltage if it is too low 2 Put to correct position 1 Treat correctly 2 Cancel out the matching error 3 Check with Pr Nd filter and adjust the wavelength 1 Contact the Service Dept of our Company position and cuvettes position and cuvettes figures energy It is not the trouble 100 54 Appendix B FYP1 and FYP2 Gantt Chart a 1 2 7 3 9 42 7 d d d l d i eee pesos TT I P Analyze Topic i KI i 98 8888998118 mee H Sanne Li 9 Seer Learn About Spectrophotometer TRG VEL TE nit ieee WW NW EEEN A me RRR RR RRRRRRR K ERRER ERRER S TT L OO O O el dd d d l d d v sls Preparing LabVIEW blocks Creating GUI Observe the Output
10. reference in completing their task As what obtained in the GUI is what they need to perform their experiment Compared to what the students did for the past time is what is called as manually But with this LabVIEW interface this experiment can be done automated Most of spectrophotometer out there can do experiments but with program codded it can do multiple task such as it can stored data which could be useful for researcher or physicians to do their research in the future 13 Objectives The main objective of this project is to design of spectrophotometry measurement system based on LabVIEW environment The second objective in this project is to improve on handling and acquiring data from samples in this case is the Tartrazine sample effectively and efficiently Other than that this project can become as reference for the spectrophotometry experiment to measure the light intensity for Tartrazine 1 4 Scope of the Project This project consists of two activities The first activity is the experiment part followed by the second activity which is the software part which will be implemented later in the experiment The total duration needed to complete the project is 8 months It is done in the Medical Electronics Laboratory MEP The first part is the experiment part is where experiment about spectrophotometry is being done manually The concentrate that is being used in this experiment is the Tartrazine The second part
11. that going to be examined Tartrazine and other sample such as glucose and enzyme can also be used as it will shows a similar straight line but with different characteristics CHAPTER 3 METHODOLOGY 3 1 Introduction This chapter discusses how the project is done by using certain methods After that this chapter will discuss how the software is implemented in the experiment Figure 8 below shows the flow method of this project UV Spectrophotometer Display LabVIEW gu Figure 8 Project Flow 15 Identify problems ale Experimental Plannin RUF Programming dl E A f Data aar a gt m Automated Measurement Figure 9 Methodology Flow of the Project The first step is to identify problem statement for the project All data and information was gained to perform this project The second step is experimental planning this is where experiments for determining concentration of a Tartrazine are done The third step is the data collecting this is where all the data receive by the RS 232 from the 752s is analyze The data obtained is received and read by port A of the computer The forth step is programming using LabVIEW to read all data that received by the port A The data was transferred by 752s via RS 232 to the computer Lastly is doing the optimization for the prototype of the spectrophotometry measurement system based on LabVIEW environment that has been designed 16 3 2
12. 1 671 017ZM 1copy Fuses 2A 2 pcs 1cm rectangular cuvette glass 2 boxes 4 pcs 1cm rectangular cuvette quartz 1 box 2 pcs 1cm optical path cuvette rack LG5 084 001 1 pair Packing list 1 copy Optional Accessories and Spare Parts 1 2 hermetical 3 4 5 6 7 8 Fuse 2A 3A Rectangular cuvette 1cm 2cm 3cm 5cm glass 1 cm quartz 5cm optical path cuvette rack LG5 084 005 S22PC data processing software package set RS 232C serial port cord Optional serial printer Praseodymium neodymium optical filter LG5 401 009 Holmium oxide optical filter LG5 401 008 39 3 Instrument Appearance and Operation Keys 1 button Itis used to automatically adjust 100 T when the transmittance indicating lamp is lit It can be pushed once more as the end position is not reached yet Display is appeared to indicate the adjustment is undergoing This button is used to automatically adjust O absorbance when the absorbance indicating lamp is lit It can be pushed once more as the end position is not reached yet Display is appeared to indicate the adjustment is undergoing It is used to increase concentration factor setting when conc factor indicating lamp is lit One action for one push The concentration factor increases rapidly when the button is kept pressing for more than 1 second Setting value is automatically confirmed after entered into rapid increasing by pressing
13. 1s added 5 If development of color is link to the concentration of the substance in solution then that concentration can measured by determining the extend of absorption of light at the appropriate wavelength 1 Beer Lambert s Law is between the solution concentration and the intensity of the transmitted light l lox 10 1 Where intensity of the transmitted light when the colored compound is added lo incident light c concentration of the colored compound distance of the light passes through the solution k Constance 2 3 The Virtual Spectrophotometer Interface The first step to do an automation for the spectrophotometry measurement is to connect the spectrophotometer to an external computer that is programmable The communication protocols is also important so that communication process can be conducted with the spectrophotometer is a way that it can understand the commands that are being sent 3 To control the UV spectrophotometer 752s by an external computer a RS 232 is needed It s method for wiring the RS 232 that connects the UV 752s to the PC is shown in Figure 1 D sub 9 pin male D sub 9 pin male connector on PC connector on RxD TAD Signal GND Figure 1 Specification for connection with RS 232 The part number of the RS 232 cable that is being used 1s 200 86408 3 wires is used 2 for input and output while the other remaining 1 is for grounding The configuration of the RS 232
14. 3 1 Introduction 3 2 Spectrophotometer 3 3 Programming Language 3 3 1 LabVIEW The experiment on Tartrazine 3 4concentration 3 5 RS 232 Electrical equivalent circuit Flow chart of the automated 3 6spectrophotometry measurement RESULTS AND DISCUSSION 4 1 Experimental result for Tartrazine Automated spectrophotometry 4 2 measurement 4 2 1 The GUI CONCLUSION AND RECOMMENDATIONS 5 1 Conclusion 5 2 Future Recommendations REFERENCES APPENDICES 13 14 16 17 18 19 21 24 25 29 30 33 34 35 36 vill FIGURE NO 1 2 LAA 10 11 12 13 14 15 16 17 18 19 20 21 ZZ 23 LIST OF FIGURES TITLE Specification for connection with RS 232 The spectro BASIC output waves Light scattered from a molecule Tartrazine light absorbance measurement Absorbance of different color at different wavelength LabVIEW data monitoring Graph absorption versus glucose concentration Project Flow Methodology Flow of the Project Spectrophotometer 752s Structure of the single beam spectrophotometer The front panel of a small LabVIEW program Sample block diagram in LabVIEW While loop function Sample of Tartrazine in different concentration Logic state of data from RS232 Pin out DB 9 DTE Pin out 25 pin DTE Flow chart for automated measurement system Absorbance value for Tartrazine at concentration Graph of absorbance vs concentration different Absorbance value for Tart
15. Indicating that the window is displaying absorbance data 9 Concentration factor indicating lamp Indicating that the window is displaying concentration factor data 10 Conc direct read out indicating lamp Indicating that the window is displaying concentration direct read out data 11 Power source socket For connecting power cord 12 Fuse socket For setting fuses 13 Main switch ON OFF power source 14 RS232C serial port For connecting RS232C serial cord 15 Sample compartment For sample testing 16 Wavelength display window For wavelength display 42 4 Installation 4 1 Installation Environment This instrument is suitable for analysis in lab Environment The following condition is required for working together with personal computer 4 1 1 Room temperature 5 C 35 C In door relative humidity is less than 85 4 1 2 Place the instrument on a sturdy working bench to avoid vibration and protect from direct sunlight and strong electromagnetic disturbance avoid dusting and corrosive gases 4 1 3 Power source voltage 220V 22V frequency 50Hz 1Hz 4 1 4 Please use warm water to clean the instrument surface do not use solvents such like alcohol and acetone to clean the instrument If the instrument is used in the site please use the original package while moving The environmental condition in the site should meet the above mentioned requirements Any special requirements should be ord
16. PSZ 19 16 Pind 1 07 UNIVERSITI TEKNOLOGI MALAYSIA DECLARATION OF THESIS UNDERGRADUATE PROJECT PAPER AND COPYRIGHT Author s full name AHMAD MUZAMMIL ZULKARNAIN AHMAD RAZALI Date of birth JUNE 15th 1988 Title SPECTROPHOTOMETRY MEASUREMENT BASED ON LABVIEW ENVIRONMENT Academic Session 2011 2012 Il declare that this thesis is classified as CONFIDENTIAL Contains confidential information under the Official Secret Act 1972 RESTRICTED Contains restricted information as specified by the organisation where research was done OPEN ACCESS agree that my thesis to be published as online open access full text acknowledged that Universiti Teknologi Malaysia reserves the right as follows e The thesis is the property of Universiti Teknologi Malaysia 2 The Library of Universiti Teknologi Malaysia has the right to make copies for the purpose of research only 3 The Library has the right fo make copies of the thesis for academic exchange Certified by a sin ma ZA _ SIGNATURE SIGNATURE OF SUPERVISOR 8806 15 56 6309 DR AKRAM GASMELSEED NEW IC NO PASSPORT NO NAME OF SUPERVISOR Date JUNE 2012 Date JUNE 2012 NOTES If the thesis is CONFIDENTIAL or RESTRICTED please attach with the letter from the organisation with period and reasons for confidentiality or restriction I acknowledge that I have studied this piece of work and in my opinion it is in accordance with the scope requ
17. Spectrophotometer A Spectrophotometer is employed to measure the amount of light that a sample absorbs From this experiment we are going to indicate reference graph for Tartrazine which is represent normal urine If development of color is linked to the concentration of the substance in solution then that concentration can be measured by determine the extent of absorption of light at the appropriate wavelength Figure 10 below shows the 752s Spectrophotometer that is used in this project Figure 10 Spectrophotometer 752s Spectrophotometers use a light source to shine an array of wavelengths through a monochromator This device then transmits a narrow band of light and the spectrophotometer compares the light intensity passing through the sample to that passing through a reference compound Different molecules or inorganic compounds absorb energy at different wavelengths Those with maximum absorption in the visible range are seen as colored by the human eye In the single beam spectrophotometer there is one or more light sources that produce a range of wavelengths The general structure of a single beam spectrophotometer is shown Depending on the desired wavelength a suitable lamp is chosen The light hits the monochromator and gets diffracted into a spectrum of wavelengths There is an adjustable aperture that only lets the desired wavelength through the glitch so that it can pass through the sample The light sensor then measures the
18. There is many other graphical programming language and they are specialized in specific areas 3 3 1 LabVIEW LabVIEW has been developed by the company called National Instruments It is basically designed for scientists and engineers Mostly the LabVIEW is used for data acquisition industrial automation and instrument control As mentioned earlier LabVIEW is based on boxes that are connected with arrows and wires and it act like a function or basically as a piece of code that has an input and output LabVIEW comes with an extensive set of functions and graphical components It 19 based on the idea of having a front panel and a block diagram There are two panels one of them is the graphical interface which on LabVIEW is very easy to create as all the components are easily placed where the user desire The components in the front panel that represent or visualize a value are also shown in the block diagram It is in the block diagram all the coding is done and where manipulation of the front panel components is done Numeric E Peas AA Kepala ee i Figure 12The front panel of a small LabVIEW program 19 Figure 13Sample block diagram in LabVIEW In LabVIEW it has standard programming functions it is to enable in creating dynamic programs The three blocks are the while loop for loop and case structure Graphically it is presented by a frame where the code to be run with such cases is placed inside Case structure is like an
19. ank sample is inserted the cover and the meter readjusted to read 100 transmittance Each absorption value needs to be correct with the blank All other measures are then made by merely inserting the samples into light path and measuring the transmittance Most spectrophotometers 21 have a build in means of direct conversion of this reading to absorbance After recording the absorbance a plot is made of the absorbance value y axis versus the concentration x axis Once calculated it can subsequently be used to determine an unknown concentration for unknown sample 3 5 RS 232 Electrical equivalent circuit The electrical equivalent circuit can determine all signal lines regardless of whether it providing data timing or control of information This is the equivalent circuit for an EIA232 signal line and applies to signals originating at either the DTE or DCE side of the connection Co is not specified in the standard but is assumed to be small and to consist of parasitic elements only Ro and Vo are chosen so that the short circuit current does not exceed 500ma The cable length is not specified in the standard acceptable operation is experienced with cables that are less than 8 meters in length Voltages of 3v to 25v with respect to signal ground pin 7 are considered logic 1 the marking condition whereas voltages of 3v to 25v are considered logic O the spacing condition The range of voltages between 3v and
20. avelength knob to both terminals of wavelength scope and press The 100 T can normally be adjusted Press while opening the sample compartment cover The 0 T can normally be adjusted 6 2 2 Checking of Transmittance repeatability 6 2 2 1 Set the wavelength to 550nm and adjust 0 T and 100 T 6 2 2 2 Put in sample with transmittance at about 40 T and with smooth absorption at nearby wavelengths e g neutral optical filter and measure sequentially for 3 times to examine the displayed values The maximum difference of values should within 0 3 T 6 2 3 Checking of Noise Level at Fixed Point 6 2 3 1 Set the wavelength at 550nm and adjust 0 T and 100 T 6 2 3 2 Set the scale as absorbance 6 2 3 3 Observe the fluctuation of figures in the display window The figures fluctuation should be within 0 002A 6 2 4 Wavelength Repeatability Checking 6 2 4 1 Set the scale as transmittance 6 2 4 2 Use Praseodymium neodymium optical filter optional accessory can be purchased from common Scientific Apparatus Co as sample which is commonly used in spectrophotometer 6 2 4 3 Use air as blank and adjust 0 T and 100 T Place the sample into the light path and read out the wavelength value corresponding to the standard peak value of sample within the range of 520 540nm 6 2 4 4 Repeat the operation in 6 2 4 3 for 3 times The wavelength deviation should not more than 1Inm 53 6 3 Recognition of Commonly Occurred Troubles and Their Treat
21. button 2 button It is used for automatically adjusting O T adjusting range lt 10 T when transmittance indicating lamp is lit This button is not used when absorbance indicating lamp is lit Overload will be occurred if this button is pressing at that time This button is used for decreasing the concentration factor setting when the concentration factor indicating lamp is lit Operation of this button is same as button 3 button For extending the predetermined function The present display value will be transmitted via RS232C port This value can be received by personal computer or by printer 40 10 9 8 7 6 Spectrumlab 752s UV VIS Spectrophotometer MODE FUNC 0 ADJ 100 ADJ A Figure 1 14 11 12 13 Figure 2 41 4 button It is used for selecting display scale The indicating lamps are ignited on the following sequence transmittance absorbance and concentration factor The sequence is advanced one step by pressing the button once a time and is cycled by pressing operation 5 Sample rack push pull rod For changing sample trough position four positions 6 Four digit LED display window For display readings and error message 7 Transmittance indicating lamp Indicating that the window is displaying transmittance data 8 Absorbance indicating lamp
22. ce and hardware such as the spectrophotometer 752s have made possible the use of the rs232 device for communication between the 752s and also computer as well as humans Rs232 19 a port for interfacing the port usually installed in devices that were meant to be interfaced and have capability of doing so This project will show that every reading from the 752s will be display directly thru computers by using the LABVIEW environment LabVIEW is a software that were used by many people especially engineers researchers and also scientist Besides that the project will also help in improving the manual reading that have in the 752s the project include designing GUI for users to plot two graph which is the photometric graph and also spectrum graph CHAPTER TABLE OF CONTENTS TITLE DECLARATION DEDICATION ACKNOWLEDGEMENTS ABSTRAK ABSTRACT TABLE OF CONTENTS LIST OF FIGURES LIST OF SYMBOLS LIST OF APPENDICES INTRODUCTION 1 1 Background 1 2 Problem Statement 1 3 Objective 1 4 Scopes of Project THEORY AND LITERATURE REVIEW 2 1 Introduction 2 2 Spectrophotometry 2 3 The Virtual Spectrophotometer Interface 2 4 Automating Spectral Measurements Raman Spectrometer Automation on 2 5 PSoC 2 6 Tartrazine light absorbance measurement 2 7 LabVIEW 2 8 Glucose Concentration Evaluation PAGE 1i U 1V vi vii 1X Xi xii OO N NO me NI DB a A OO 10 11 vii 2 9 Conclusion of Literature Review METHODOLOGY
23. centration value The data obtained is then listed down in Microsoft Excel and later graph absorbance versus concentration 1s plotted The graph is shown as in Figure 7 below 12 Abs J U 0 40 GO BD 100 120 140 160 3b Glucose concentration mg 100mL Figure 7 Graph absorption versus glucose concentration A calibration graph plotting absorbance against concentration of Glucose in the range 10 Ilmg 100mL to 140 1mg 100mL was determined and linear fitted by polynomial regression The characteristics of the calibration graph and the statistical parameters for determination of glucose under optimum conditions are summarized The concentration calibration scale resulted in Figure 7 was fitted linear by polynomial regression with the corresponding equation y 5 72111 E 3 x 3 6226E 5 2 Which x represents the value of Glucose sample concentration and y is the absorbance value at 267 nm for the same sample 12 2 0 Conclusion of Literature Review For this project LabVIEW will be used to interface the 752s This is because using LabVIEW environment is easier and commonly used by scientist and also using LabVIEW is used to create GUI for user to use to measure the light intensity for Tartrazine in this project The 752s is used in this project as it is the instrument that is available in the MEP laboratory 752s is easy to use and its manual is attached in the appendices This project uses Tartrazine as sample
24. ent is widely used in medical science and hygiene clinical analysis biochemistry petroleum chemical industry environmental monitoring and quality control department for qualitative and quantitative analyses The features of the instrument are Four digits LED display e Non spherical optical path of light source CT grating monochromator 6 Large sample compartment 4 positions sample cuvette rack optional 5cm optical length rectangular cuvettes e Auto zero and auto 100 T adjustment e Concentration factor setting and direct read out ability RS 232C serial port interface attached 2 Instrument Specificatios and Standard Accessories Optical system Diffraction grating C T monochromator e Wavelength range 200 960nm e Light source Penson L2D gt long life high stable deuterium lamp and RoYal long life tungsten lamp e Receiver Penson 1226 UV receiver 6 Wavelength accuracy 2nm e Wavelength repeatability 0 5 nm e Transmittance accuracy 0 5 t NBS SRM930D 6 Transmittance repeatability 0 3 T 6 Spectrum bandwidth 2nm e Stray light lt 0 2 t 360nm NaNO gt 220nm Nal 38 e Display scales T 0 0 199 9 A 0 3 2 999 F 19999 C 0 9999 Power source 220V 22V 50Hz 1Hz 6 Dimension 370 X 320 X 240 e Weight Net 7 5kg Gross 10kg 6 Standard Parts List Main instrument 1 set Power cable 1 pc Instruction manual 1 copy por ees ek 0 SDE ee ES 5 Quality certificate of product LG
25. ered at time of purchasing as product for special purposes 4 2 Unpacking and Inspection Note The instrument and computer are packed in carton outer wooden case can be requested for distance transportation 43 4 2 1 Please check the integrity of outer package before unpacking Please contact transportation insurance agency when the package is found not intact or left some indications of collision or water immersion 4 2 2 Tear off the sealing tapes and take out the instrument and computer carefully Please keep the outer package in place for re use Check the standard configuration and optional accessories and spare parts according the attached packing list Please contact transportation insurance agency when the package is found not intact or left some indications of collision or water immersion 4 3 Installation Remove various fixing tapes used during transportation and clean the surface Check the power source conversion switch situated on the instrument base to see if the position indicated is the same as the local voltage Place the instrument on a sturdy working bench The distance of the bench from the wall is about 10 cm Connect the attached power cord to the electric power socket in the lab 5 Operations 5 1 Routine Basic Operations 5 1 1 Preheating Turn on the power switch on the instrument The lamp and the electronic parts need be waiting to reach heat balance the operation of the instrument should theref
26. how the program suit to gives automated measurement with GUI friendly for user maik aten hanifi INPUT port of SPECTROPHETOMETE E zal E vis SERIAL Figure 24The block diagram to call data form RS 232 PSMvi Block Diagram Ze Edit View Project Operate Tools Window Hep 2 1 gt HIS Ragi S gt et Application Font Tas lR gt nad e Searct 4 PF ABSOR vah H Enter your value here INTERCEPT POINT r L x G By Enter your Absorbance value for Absorbance vs Wavelength graph here ii l 0 BS Absorbance Vs Wavelength Graph mil S l Figure 25 The full block diagram for the automated spectrophotometry measurement 30 4 2 1 The GUI Figure 26 shows the full GUI image of the automated spectrophotometry measurement system It consists of the input port part which allows the user to choose which input port they desire to obtained data Next is the plotting absorbance versus concentration graph where user have to enter their data of absorbance and concentration by their own to obtain a straight line graph or can be said as the photometric mode Lastly is the plotting the absorbance versus wavelength data The wavelength is fixed User need to key in their data of absorption to obtain its graph or can be said as the spectrum mode Other than that this GUI also shows the slope and interception line of the graph Wy NATIONAL P7 INSTRUMENTS HF LabVIEW Evaluation Software
27. irement and quality for the purpose of awarding the Bachelor of Engineering Electrical Medical Electronics 7 Signature l LAA Name of Supervisor DR AKRAM GASMELSEED Date JUNE 2012 SPECTROPHOTOMETRY MEASUREMENT BASED ON LABVIEW ENVIRONMENT AHMAD MUZAMMIL ZULKARNAIN BIN AHMAD RAZALI A report submitted in partial fulfillment of the requirements for the award of the degree of Bachelor of Engineering Electrical Medical Electronics Faculty of Electrical Engineering Universiti Teknologi Malaysia JUNE 2012 I declare that this thesis entitled Spectrophotometry Measurement Based on LabVIEW Environment is the result of my own research except as cited in the references The thesis has not been accepted for any degree and is not concurrently submitted in candidature of any other degree Signature Ha TT Name Ea Date a TE Aisi Nesta ce ee This thesis is specially dedicated to my beloved mother and father brothers and friends ACKNOWLEDGEMENT Alhamdulillah Thank you to Allah SWT whom with HIS willing has given me the opportunity to complete my final year project The preparation of this thesis would not have been possible without the support and endless efforts of a large number of individuals Firstly I would like to express my deepest thanks to my supervisors Dr Akram Gasmelseed His supervision and support has been valuable towards the progression and smoothness of my final year project W
28. is where program coded using LabVIEW is being used to obtain result from the same experiment but the different is that the data obtained is automated CHAPTER 2 THEORY AND LITERATURE REVIEW This chapter includes the study on previous students work relevant information from technical paper and published journal In this chapter spectrometer 752s 1s explained while other method of automation using varies of spectrometers is explained Other than that this chapter will also explain how RS 232 helps in interfacing in this project Tartrazine and application of LabVIEW environment will also be explained briefly in this chapter 2 1 Introduction Spectrophotometers use a light source to shine an array of wavelengths through a monochromator This device then transmits a narrow band of light and the spectrophotometer compares the light intensity passing through the sample to that passing through a reference compound Different molecules or inorganic compounds absorb energy at different wavelengths Those with maximum absorption in the visible range are seen as colored by the human eye 6 2 2 Spectrophotometry There are two types of UV Vis spectrophotometer machines single beam and double beam These differ in how they measure the light intensity between the reference and test sample Double beam machines measure the reference and test compound simultaneously while single beam machines measure before and after the test compound
29. ithout his continued support and interest this thesis would not have been the same as presented here Thus his cooperation is greatly appreciated Also deepest appreciation goes to my family for their encouragement and support throughout my final year project In addition my fellow course mates also deserved to be recognized for their support My sincere appreciation also extends to my friends and others who have provided guidance at various occasions Thank you very much ABSTRAK Kemajuan terkini dalam perisian komputer keupayaan peranti komputer dan perkakasan seperti 752s spektrofotometer telah dibuat mungkin penggunaan peranti RS232 untuk komunikasi antara komputer manusia serta 752s dan juga RS232 adalah sebuah pelabuhan untuk pengantaramukaan pelabuhan yang biasanya dipasang di peranti yang dimaksudkan untuk diantaramukakan dan mempunyai keupayaan untuk berbuat demikian Projek ini akan menunjukkan bahawa setiap bacaan dari 752s akan memaparkan secara langsung melalui komputer dengan menggunakan persekitaran LabVIEW LabVIEW adalah perisian yang telah digunakan oleh orang ramai terutamanya jurutera penyelidik dan juga saintis Selain itu projek ini juga akan membantu dalam meningkatkan bacaan manual yang mempunyai dalam 752s projek termasuk merekabentuk GUI bagi pengguna untuk memplot dua graf iaitu graf fotometri dan juga graf spektrum vi ABSTRACT Recent advances in computer software capability of the computer devi
30. ment Troubleshooting 1 Turn on the power 1 Power source has not been switch and the connected instrument no response 2 Power fuse broken 3 Inserters in the instrument are loosen 2 Display unstable 1 Preheating time is not enough 2 AC power source unstable 3 Too large environmental vibration 4 Poor contact of inserters 3 Energy cannot be detected 1 Light source lamp is not lit 2 Light shuttle is not opened 3 Light is completely blocked by cuvette rack 4 No signal output from the receiver 4 100 T can not be adjusted 1 Light energy insufficient 2 Wrong position of cuvette rack 5 Abnormal light measurement 1 Wrong treatment of sample 2 Not match of the cuvettes 3 Too large wavelength deviation 1 Serial communication circuit occurs trouble 6 Data cannot enter into the upper order software 1 A check the power plug It should be securely connected to 198 240V B Voltage on the base of the instrument should be at adaptive switch position C Check the power cord if it is not broken D Check the instrument power switch if it is not damaged 2 Replace fuse 3 Re insert the inserters 1 Preheat the instrument for 30 minutes 2 Keep the power source at 220V 22V and without fluctuation 3 Change working environmental condition 4 Open instrument cover and re insert each inserter 1 Light source lamp is damaged and should be replaced or no voltage output from power source PCB 2 Check flexibility
31. o take samples of the absorbance over a range of wavelength that has been fixed As the program reads the data form the spectrophotometer s data buffer user has to key in the value to a given space to produce a graph of absorbance versus wavelength It is also gives user a good overview of the parameter set with the user friendly graphical user interface 34 5 2 Future Recommendation In order to further improve this automated system there are some recommendation may be applied Firstly is to implement an automated data capture where all the data transmitted from the spectrophotometer to the controller PC is automated captured an automatically saved in a storage data This will help in reducing time rather than inserting the reading manually in the GUI Secondly is to improve in the photometric and spectrum mode so that it will be able to add post process data analysis and also capable to open and show old measurements in the program The post processing have been use in MATLAB with the data is stored to the PC Lastly is improving the range of measurement rather than just Tartrazine maybe the automated system may also be measuring other concentration such as glucose or enzyme instead 35 REFERENCES 1 Karolina Elisabeth Nilson 2010 Spectrophotometric Measurement for the Analysis of Enzymatic Processes 2 Syamsul Rizal AbdShukor Reza Barzin and Abdul Latif Ahmad 2008 Computer Based Control For Chemical System
32. ore be started after preheating for 30 minutes Please adjust 0 T and 100 T at all time when the instrument need be operated immediately after start up 5 1 2 Zero Adjustment Purpose To calibrate the both terminals of basic scale readings in cooperation with the adjustment of 100 T in order to enter into accurate measuring status 44 Adjusting stage After preheating when change the measuring wavelength or after some operation or before performing high precise measurement Operation Open the sample compartment cover shut off the light shuttle or block the optical path in the sample compartment with opaque materials and then press button to adjust zero automatically 45 5 1 3 100 T Adjustment Purpose To calibrate the both terminals of basic scale readings in cooperation with the zero adjustment in order to enter into accurate measuring status Adjusting stage After preheating when change the measuring wavelength or after some operation or before performing high precise measurement Generally 100 T adjustment should be done for once before zero adjustment in order to reach the automatic gain within the instrument Operation Place a blank sample into the sample compartment optical path as background Close the sample compartment cover open the light shuttle at the same time press 100 button to adjust 100 T automatically press once more if deviation still existed after above adjustment Note Re adj
33. ple absorbance characterization in a wavelength range within 350nm 700nm This part of the program was added later in the project to be a part of the automated of the 752s It 1s possible to choose the wavelength range for the spectrum and also choose between measuring the absorbance transmittance or energy spectrum The scan resolution the number of scans and the display mode are also parameters that can be defined The graphical interface gives the user a clearer overview of the parameters that are defined for the test 33 CHAPTER 5 CONCLUSION AND RECOMMENDATION 5 1 The program This program was created to invent an interface to control the spectrophotometer 752s First the communication between the 752s and a controller PC needed to be created A user friendly GUI was formed on the controller PC with the graphical programming language of the LabVIEW Two modes the spectrum mode and the photometric mode were created to control different measurement of the spectrophotometer Besides that the GUI also has the input reading receive from the spectrophotometer The photometric mode summons user to put the value that shown in the input reading in the yellow box in the middle of the GUI Whatever value the user see they will have to put in that value in the photometric mode The graphical user interface is easy to use and gives the user a good overview of the parameters used in the measurement The spectrum mode however is created t
34. port is as follows Transmission rate 9600 bps Data bits 7 bits Stop bit 1 bit Parity bit Odd 2 4 Automating Spectral Measurements Optical coating technicians normally measure a single witness sample from each coating In many cases the witness reliability characterizes the entire batch but as spectral requirements become more critical and filters more selective it eventually become necessary to measure each part It is known that custom automation solutions can be implemented for relatively low cost if off the shelf hardware and software components are utilized 4 The design was to acquire the sufficient data with Microsoft Excel VBA Visual Basic for Applications FilmStar MEASURE OmnicSB scw File Setup Evaluate Spectra Tools Help Bi B amp amp S08 Esamle Fl 123 4 5 6 Transmission Spectrum 71700 T T TR UE D S TTT S HOS 1 9 Transmittance M Scan Redraw Color Figure 2 The spectro BASIC output waves Automation should be supportable and also as straightforward as possible By adapting a database application with millions users will eliminate numerous unforeseen problems which occur By using Windows compatibility which the FileMaker as data acquisition software is the key and therefore propose an Excel automation test Therefore it can be readily controlled and be considered as automation for obtaining data 2 5 Raman Spectrometer Automation on PSoC Raman spectroscopy use
35. r can be used in the next start up of the instrument without repeat the measurement of the known standard sample The concentration of the sample can be directly read out only by inputting this factor The procedure is as follows 50 1 Start up preheating set wavelength put in the background solution and adjust 0 and 100 T Set scale as concentration factor 5 1 6 3 Press orl to display the value as inputted factor 4 Set scale as Conc direct read out 5 1 6 Put in unknown sample solution 5 1 5 E Read out displaying value as concentration i 6 Instrument Mentenance and Troubleshooting 6 1 Routine Maintenance of Instrument 6 1 1 Operation Notices 6 1 1 1 Please observe to meet the requirements in 4 1 during daily use of the instrument 6 1 1 2 Do not use organic solvents such as ethyl alcohol and ethyl ether to clean the surface of the instrument Use dust proof cover when the instrument ts not in use 6 1 1 3 Use petroleum ether to clean the cuvette after use and gently wipe dry with lens paper Store the cuvette in the cuvette box 6 1 2 Inspection after Opening the Cover Instrument cover should be opened when it is necessary to inspect mechanics optics and electric circuit status as well as to replace light sources Procedures are as follows 6 1 2 1 Cut off the electric source 51 6 1 2 2 Uncover the upper cover of the wavelength adjusting knob and dismount the wavelength adjusting knob 6 1 2
36. razine at different wavelength Graph of absorbance versus wavelength PAGE 10 11 12 14 15 16 17 18 19 19 20 22 22 23 24 25 26 21 24 25 26 2J 28 The block diagram to call data form RS 232 The full block diagram for the automated spectrophotometry measurement GUI for the automated spectrophotometry measurement GUI for the photometric mode GUI for the spectrum mode 29 29 30 31 32 LIST OF SYMBOLS BPS Bit per second AC Alternating current LabVIEW Laboratory Virtual Instrumentation Engineering Workbench PC Personal computer mmol l milimoles per litter mg l milligram per litter ma miliampere DTE Data terminal equipment DCE Data communication epuipment Nm nanometer Xi xii LIST OF APPENDICES APPENDICES TITLE PAGE A Spectrophotometer 752s User Manual 58 B FYP1 and FYP2 Gantt Chart 60 CHAPTER 1 INTRODUCTION This chapter gives some brief explanations of the project The background which will be presented in sub 1 1 followed by the problem statements which will be presented in sub 1 2 followed by the objectives which will be presented in sub 1 3 and lastly the project scopes which will presented in sub 1 4 1 1 Background Using hardware instrumentation especially a traditional device will certainly be hard coded to work in a preferred way by user The procedure to obtain measurement is pre defined Virtual instrumentation is
37. s 8 bits Stop bits one bit 5 1 8 Data Transmittion Testing Example The function of serial port can be checked by simple Basic program if the main instrument is connected to the personal computer according to the specification defined in 5 1 8 The following program is used only as an example to illustrate the interface ability of the spectrophotometer and to demonstrate how to get data from the spectrophotometer 10 OPEN COM2 9600 N 8 1 CS DS CD AS 2 20 FOR X 1 TO 100 30 DAS INPUT 8 2 40 PRINT DAS 50 NEXT X 70 END Note This program is compiled by Gwbasic it can be adaptively modified when using Qbasic to compile the program Note An optional S22PC data processing software package specially useful for this instrument is provided by the Company at user s choice This software can be installed in Windows 98 or Windows Me operational platform to conveniently collect transform calculate tabulate and to be used in statistics large volume storage and in the treatment of spectrum data It can directly express the standard curve test the spreading points in the graph and can establish testing model by lest square method and high order curve fitting method It can provide perfect support to the storage and management 48 5 2 Operations in Application 5 2 1 Transmissivity Determination of Transparent Materials 5 1 1 5 1 5 5 1 6 4 Coarseadj of 100 T 5 1 3 5 1 2 6 Adjustioowr 5 15 8 Dataread out 5
38. s Using LabVIEW in Conjunction with MATLAB UniversitiSains Malaysia 3 Christoph Wagner Andreas Genner Georg Ramer and Benhard Lendl Advanced Total Lab Automation System ATLAS Vienna University of Technology 4 Xiang Yang LabVIEW Program for I V Measurement Department of Materials Science and Engineering University of Pennsylvania 5 J Jayapandian R Kesavamoorthy and A K Arora 2009 Raman Spectrometer Automation On a Single Programmable System On Chip PSoC Kalpakkam 603 102 Tamil Nadu India 6 FaezahMd Noor SittAsmah and SyazalinaMohdSobani 2011 UV Spectrophotometer UniversitiTeknologi Malaysia 7 Robert F Tinker John W McWane The Spectrophotometer A Module On the Spectra Properties of Light McGraw Hill 1975 8 Beers RF JrSizer I W A Spectrophotometric Method for Measuring the Breakdown of Hydrogen Peroxide by Catalase J BiolChem 195 133 140 9 Vital Buckin EugencyKudryashov and Breda O Driscoll 2002 High Resolution Ultrasonic Spectroscopy for Material Analysis Appendices Appendix A Spectrophotometer 752s User Manual Product Standard No Q SEEK3 Spectrumlab 152s UV VISIBLE SPECTROPHOTOMETER Instruction Manual 37 1 Applications and Features The 752sUV Visible soectrophotometer is a concise easy operated general use spectrophotometric instrument It can measure transmittance absorbance and direct reading within the wavelengths of 200 960 nm This instrum
39. s a light scattering technique how it actually works 19 that photon of light interacts with number of sample to produce scattered radiation energies as show in Figure 3 This Raman spectroscopy is very rich in information and it has become very important tool as analytical and research It can also be used as wide range measurement for chemical identification also Other than that characteristic of molecule structure effects of bonding and carbon nano materials can also be determined 5 Figure 3 Light scattered from a molecule Figure 4 shows how Raman spectrometer setup by using a single programmable System on Chip is interfaced with PC and it is then controlled by virtual instrument program Thus it will then provide wider range of measurement and also preset work and time under window environment on PC 5 Vionochromator Monochromator Drive Pulse Raman Spectrometer setup Personal Computer Figure 4 Block diagram of Raman spectrometer in PSoC way 2 6 Tartrazine light absorbance measurement Figure 5 shows that the absorbance Based on theory violet light is absorbed at approximate wavelength 400nm so we can see yellow color instead violet because the wavelength for violet light is from 380 to 450nm This abides the maximum absorbance for yellow color is at wavelength 430nm 6 The wavelength of the maximum of the absorption will give information regarding on the structure of the molecule of ion Molecule consis
40. ts of atom held together by balance force When impinging radiation passes through the material it absorbed only at frequencies corresponding to molecular modes of vibration Absorbance doesn t have any units because it s the ratio of the amount of light that passes through a solution compared to the amount of light that is passed into it 10 Observed Color of Color of Light Approximate Compound Absorbed Wavelength of Light Absorbed 550 530 nm 450 nm Figure 5Absorbance of different color at different wavelength 2 7 LabVIEW LabVIEW is a program produced by National Instruments used to automate testing and data gathering It is basically a graphical programming language where the user is able to set up the program to manipulate and store data 1 The thing which makes this software so unique and popular amongst scientists and engineers is that it requires no text based code such as programming It utilizes a unique method which is to play around with blocks in order to visualize data flow An example of a LabVIEW project is shown in Figure 6 11 Figure 6 LabVIEW data monitoring 2 8 Glucose Concentration Evaluation Data from the UV Spectrophotometer is extracted from several of concentration level of a glucose solution Glucose concentration is prepared earlier before the experiment starts The concentration is fixed into certain value and all the reading taken is the absorbance value based on the fixed con
41. ult obtained from the manual experiment is shown And then the result from the same experiment is Shown but this time it 19 automated using LabVIEW without manual calculation 4 1 Experimental result for Tartrazine Below is the result for absorbance versus concentration for Tartrazine This result can be used as a reference for measure concentration of unknown sample Concentration 0 0045 0 009 0 595 0 018 0 589 0 036 0 671 0 045 0 717 Figure 20 Absorbance value for Tartrazine at different concentration 26 Graph of Absorbance vs Concentration for Tartrazine 08 07 06 05 04 y 4 088x 0 528 R 0 936 03 Absorbance 0 2 4 01 0 4 0 0 005 001 0015 002 0 025 003 0 035 0 04 0045 0 05 Concentration Figure 21 Graph of absorbance vs concentration Note that y mX c where y absorbance X concentration m gradient c y intercept From the graph we obtain that y 4 088X 0 528 R 0 936 R is 0 936 This value is approaching which represents how closely the data point to match the regression line Generally wavelength for yellow color is 570 590nm We adjust the wavelength to gain the maximum absorbance of Tartrazine for different concentration From the experiment we found that the maximum absorbance is at 570nm and the absorbance turns out to be higher as the concentration of the 27 solution get higher This shows the Beer s Lambert Law is obe
42. ustment of auto gain system may influence the O T when making 100 T adjustment Please check the O T after gain re adjustment had been done The 0 button should be adjusted once again if any change is occurred 5 1 4 Wavelength Adjustment Use the only knob wavelength adjusting knob on the instrument to adjust the present testing wavelength The wavelength reading is shown on the wavelength indicating window which is situated at the left side of the adjusting knob Wavelength reading should be taken at vertical position in order to avoid reading error Note The filters are situated automatically by micro computer the display window will show to indicate the change over of filters during turning the knob This is a normal operation 46 5 1 5 Changing of sample trougth position for entering the lightpath into the sample The sample rack in the standard set of instrument provides 4 sample trough positions These positions can be changed by using sample rack push pull rod which is in front of the instrument Open the sample compartment cover to observe the position of sample in sample trough The position nearnest the operator is position 0 and then followed by positions 1 2 and 3 Correspondingly push the rod into the innermost is position 0 the positions by the order while pulling out are 1 2 and 3 The operator can sense the position while the rod is
43. yed where there is a linear relationship between absorbance and concentration 5380 CO 550 CO 60 9 6380 e 650 O a HUU 00 U Figure 22 Absorbance value for Tartrazine at different wavelength Graph of Absorbance vs wavelength for Tartrazine 0 25 0 2 0 05 0 n gt 100 200 300 400 500 600 700 800 Wavelength nm Absorbance oO G uw C3 H Figure 23 Graph of absorbance versus wavelength 28 Figure 23 shows that the maximum absorbance at wavelength 430nm Based on theory violet light is absorbed at approximate wavelength 400nm so we can see yellow color instead violet because the wavelength for violet light is from 380 to 450nm This abides the maximum absorbance for yellow color is at wavelength 430nm When the comparison between theoretically and experimentally we can see that the value from experimental approximate with theory concept The wavelength of the maximum of the absorption will give information regarding on the structure of the molecule of ion Molecule consists of atom held together by balance force When impinging radiation passes through the material it absorbed only at frequencies corresponding to molecular modes of vibration Absorbance doesn t have any units because it s the ratio of the amount of light that passes through a solution compared to the amount of light that is passed into it 29 4 2 Automated spectrophotometry measurement This part will show
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