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Contents
1. 2004 John Wiley amp Sons Inc 61 62 MONITORING THE PRESENCE OF HYDROCARBONS IN AIR TABLE 6 1 Composition of Unleaded Gasoline Percent Range Exposure Limits Component by Weight ppm Benzene 0 3 1 5 Butane 4 6 800 Cyclohexane 0 1 300 Ethylbenzene 0 2 100 125 Heptane 6 8 400 500 Hexane 6 8 50 500 Pentane 9 11 600 1000 Toluene 10 12 100 200 Trimethylbenzene 0 3 25 Xylene 8 10 100 Source http www bpdirect com But what exactly are the risks of exposure Laboratory animals rats and mice exposed to high concentrations of gasoline vapors at 67 262 and 2056 ppm showed kidney damage and cancer of the liver n Heptane and cyclohexane can cause narcosis and irritation of the eyes and mucous membranes In studies using rabbits cyclohexane caused liver and kidney changes Benzene a known human carcinogen has an eight hour exposure limit of 0 5 ppm Studies have shown that exposure to benzene vapor induce leukemia at concentrations as low as 1 ppm Trimethylbenzene isooctane has an eight hour exposure limit of 25 ppm and above this limit can cause nervousness tension and anxiety as well as asthmatic bronchitis n Hexane has been shown to cause peripheral nerve damage and hexanes show narcotic effects at 1000 ppm Toluene can cause impairment of coordination and momentary memory loss at 200 to 500 ppm Palpations extreme weakness and pronounced loss of coordination can occur at 500 to 1500 ppm The eight hour expos2. BR lt gt to tA gt 300 0 500 1000 1500 2000 Depth in Ice Core m a Figure 5 4 CH4 b and c temperature data from the Vostok ice core study Data from http ingrid ldgo columbia edu 54 GLOBAL WARMING DETERMINING IF A GAS IS INFRARED ACTIVE 310 J e e 230 210 190 CO Concentration ppmv 170 150 0 500 1000 1500 2000 Depth in Ice Core m b 5 4 o o g 2 2 ey 0 2 2 4 g amp 6 jg o 8 c s 6 10 0 20000 40000 60000 80000 100000 120000 140000 160000 Age years c Figure 5 4 Continued returning to Figures 5 1 and 5 2 and noting which gases absorb or trap energy in Earth s atmosphere Now we combine the CO data from the Vostok ice core and the Mauna Loa data set to create Figure 5 5 Note in the figure that the direction of time changes going back in time from left to right This figure contains data going back 160 000 years and we notice two distinct spikes in CO concentration and in temperature if we look again at Figure 5 4 The important point to note in Figure 5 5 is the rate at which the CO and temperature has changed over time The natural BACKGROUND 55 400 Mauna Loa Data Set PS 350 300 250 200 150 CO Concentration ppmv 100 Vostok Core Data 150 0 150000 100000 50000 0 Years in the Past
3. Figure 5 5 Combined data from the Vostok ice core and the Mauna Loa studies Note the rapid change in CO levels during the present time The Mauna Loa data are from Keeling 1995 1996 the Vostok ice core data are from Barnola et al 1987 Genthon et al 1987 and Jouzel et al 1987 Data from http ingrid ldgo columbia edu change in CO around 130 000 years ago took more than 30 000 years to go from the lowest to the highest concentration Similarly the recent climb in temperature took approximately 20 000 years to reach its current level This is in contrast to the drastic rate of change that is present in the Mauna Loa data set This 50 ppm change in CO concentration has occurred in only 50 years and most predictions of future atmospheric CO concentrations if we continue to consume petroleum products at current rates are in the range 700 to 800 ppm by the year 2100 locate this point in Figure 5 5 This is the global warming that concerns us directly Some people call for more study of the problem and wish to maintain our use of fossil fuels to preserve our economic status but based on the data presented here this is one experiment that we may not wish to conduct Although many scientists accept that global temperatures are rising they are less in agreement about the effects of global warming Most however agree on the following predictions e Warmer temperatures averaging 5 to 10 by the year 2100 e Loss of coastal
4. 10 C min to 200 C Hold for 5 minutes or less e Column DB 1 or DB 5 e Injection volume 1 uL e Integrator settings Attenuation 3 Threshold 3 e Retention times Table 6 4 Equipment and Glassware 10 mL Teflon septum capped vials for extracting sample charcoal Needle nosed pliers for breaking the sample containers Capillary column gas chromatograph 1 2 and 5 mL volumetric pipets PROCEDURE 67 PROCEDURE Week 1 1 Your instructor will assign you times and dates to sample at a local gasoline filling station Each group will take one sample Use a piece of plastic tubing to position the sample point at shoulder level If you are using carbon disulfide as your extraction solvent take a sample over a 5 to 10 minute period It typically takes 0 75 to 1 5 minutes to fill an empty tank so you will have to take a composite sample while filling several cars Remember to turn the pump off between cars If you are using pentane as your extraction solvent you will need to sample for 10 minutes Cap the ends of the sampling tube with the caps included in your kit when you are finished Week 2 4 Start the GC and run your calibration standards while you prepare your samples Extract desorb your sample tubes as illustrated by your laboratory instructor You will need to place the charcoal from the front and back in two separate vials Add 1 00 mL of your extraction solvent containing decane your int
5. and then your unknown samples making duplicate injections as time permits Remember to record any instrument problems in the logbook as you sign out 5 Use the linear least squares Excel program to analyze your data FAAS Analysis 1 First turn on the FAAS unit and lamp This will allow the system to warm up while you prepare your calibration standards and sample dilutions 80 DETERMINATION OF AN ION BALANCE FOR WATER SAMPLE 2 Note that all solutions dilutions should be made in 1 HNO to preserve your samples and standards 3 Prepare your FAAS calibration standards as described earlier 4 Dilute your water sample 1 500 1 250 1 100 and 1 1 and analyze each sample from low to high concentration until you determine which dilution is appropriate for analysis Analyze each sample twice as time permits and determine the most appropriate dilution based on your calibration curve 5 Analyze each metal separately 6 Use the linear least squares Excel program to analyze your data Waste Disposal After neutralization all solutions can be disposed of down the drain with water ASSIGNMENT 81 ASSIGNMENT Calculate the ion balance for your water sample based on the undiluted solution 82 DETERMINATION OF AN ION BALANCE FOR WATER SAMPLE ADVANCED STUDY ASSIGNMENT 1 Why is the electroneutrality of a water sample important to document 2 How do the anion and cation content affect toxicity 3 Using your library s
6. areas to flooding e Damage to coral reefs bleaching e Increased incidence of violent weather Increased outbreaks of diseases new and old Changing regional climates wetter or drier depending on where you live 56 GLOBAL WARMING DETERMINING IF A GAS IS INFRARED ACTIVE Figure 5 6 Vibrational structures for THEORY In the background section we saw which greenhouse gases absorb IR radiation and at what wavelengths But what actually makes a gas IR active There are two prerequisites for a gas to be IR active First the gas must have a permanent or temporary dipole Second the vibration of the portion of the molecule having the dipole must be at the same frequency as the IR radiation that is absorbed When these two criteria are met the gas molecule will absorb the radiation increase its molecular vibrations and thus retain the heat in the atmosphere This is why gases such as O and are not IR active they do not have permanent or sufficiently temporary dipoles Molecules such as chlorofluorocarbons CFCs on the other hand have permanent dipoles and are very IR active actually this is the only connection between global warming and ozone depletion CFCs are active in both cases However what about symmetrical molecules such as CO and To understand how these molecules are IR active we must draw their molecular structures Figure 5 6 shows several possible vibrational structures for CO The arrows indica
7. by dissolving 1 4282 g of NaHCO and 1 9078 g of Na CO in 100 mL of deionized water This 100 fold concentrated eluent solution is then diluted with 10 0 mL diluted to 1 00 L of deionized water and filtered it through a 0 2 mm Whatman nylon membrane filter for use as the eluent Store the concentrated solution at 4 C Deionized water is also a reagent for washing the system after completion of the experiment For each run set the flow rate at 1 5 mL min The total cell value while running should be approximately 14 mS Inject one or two blanks of deionized water before any standards or water samples in order to achieve a flat baseline with a negative water peak at the beginning of the chromatogram The composition of these solutions will vary depending on your instrument Consult the user s manual IC Standards Prepare a stock solution of the anions present in the synthetic water chloride nitrate and sulfate for each anion For chloride 0 208 g of NaCl should be dissolved in 100 0 mL of deionized water yielding 1 26 g of CI L Dilute this stock solution 1 10 to give 0 126 g or 126 mg of CI per litre of working standard For nitrate dissolve 0 155 g of Ca NO3 in 100 0 mL of IN THE LABORATORY 77 deionized water to yield 1172 mg NOj L For the sulfate stock solution dissolve 15 113 g of MgSO in 100 0 mL of deionized water to yield 120 600 mg of SOT L An additional 1 1 100 mL dilution of the sulfate stock may aid in the prepa
8. dichlorodiphenyltrichloroethane Methoxychlor Endosulfan I not added to purge system but used as a GC internal standard You will need in addition e Tenax resin chromatography grade e Deionized water 40 DETERMINATION OF HENRY S LAW CONSTANTS Equipment and Glassware e Sherer impingers one per student group available from Ace Glassware use the frit that allows gas to exit at the bottom of the impinger e Pasteur pipets filled with Tenax resin e 15 mL glass vials equipped with a Teflon lined septum 12 per Sherer impinger setup or student group e Tygon tubing e Brass or stainless steel fine metering valves e Brass or stainless steel tees PROCEDURE 41 PROCEDURE In the lab the Sherer impinger will already be set up and the purge solutions prepared Your instructor will go over the setup and show its proper operation Figure 4 4 Before you start the experiment you will need to prepare Tenax resin sampling tubes Tenax is a resin that has a high affinity for hydrophobic compounds and will absorb them when water or gas containing analytes is passed through the resin Prepare the tubes by taking a glass Pasteur pipet and filling the narrow end with a small amount of glass wool Next place the Tenax resin tube in the pipet leaving enough room for more glass wool at the constriction This will leave about 1 to 2 cm of empty space at the top of the pipet we will need this to add solvent to the pipet to desorb the analytes
9. flow rate and if needed adjust it to 0 500 L min Sample at the following times to obtain a complete purge profile 20 minutes 40 minutes 1 00 hour 1 50 hours 2 00 hours 3 00 hours 4 00 hours 5 00 hours 7 00 hours 17 0 hours 29 0 hours Desorbing the Tenax Resin Tubes 7 10 11 12 Place the Tenax resin tube in small clamp attached to a ring stand Lower the tube so that it just fits into a 15 mL glass vial Pipet 5 00 mL of pesticide grade acetone onto the top of the Tenax resin trap Allow the acetone to reach the top of the resin with gravity You may have to apply pressure with a pipet bulb to break the pressure lock caused by bubbles in the tube but be careful not to blow more air into the tube After the second or third application with a bulb the acetone should flow with gravity The reason for adding acetone is to remove any water from the resin tube that will not mix or be removed by the hydrophobic isooctane Pipet 5 00 mL of pesticide grade isooctane onto the resin trap After the isooctane has passed through the resin trap force the remainder of the isooctane out of the pipet with a bulb Remove the vial from below the tube being careful not to spill any of the contents Add 10 0 mL of deionized water to the extraction vial and 0 25 g of NaCl NaCl will break any emulsion that forms in the solvent extraction step Add 8 0 uL of a 32 70 ppm Endosulfan I in isooctane that your instructor will ha
10. online search engine find an example in the literature describing the toxicity of a complexed metal ion The two important jeurnals Environmental Science and Technology and Environmental Toxi cology and Chemistry Journal should be included in your search 4 Complete Table 7 2 to determine the net electroneutrality of the water sample Is the solution balanced with respect to cations and anions TABLE 7 2 Calculation of the Electroneutrality of Seawater Concentration Molar Concentration Charge Total Ion mg L mol L Balance Ion Balance Cations 4 208 Mg 1 320 Na 11 012 K 407 Total cations Anions HCO 122 19 780 SO 2 776 Total anions Net difference Source Based on data in Berner and Berner 1996 8 MEASURING THE CONCENTRATION OF CHLORINATED PESTICIDES IN WATER SAMPLES Purpose To determine the concentration of chlorinated pesticides in a water sample To use a capillary column gas chromatograph equipped with an electron capture detector BACKGROUND Chlorinated pesticides are considered to be ubiquitous in the environment due to their refractory behavior very slow chemical and biochemical degradation and widespread use For example chemicals such as DDT and PCBs have been observed in water soil ocean and sediment samples from around the world Although the production and use of these chemicals has been banned in the United States since the 1970s many countries with the h
11. s surface but this time the satellite is pointed at Earth instead of the Sun Note the strong absorbance by atmospheric constituents primarily water methane and carbon dioxide By absorbing the IR radiation instead of letting it pass freely into space the gases heat Earth s atmosphere The amount of global warming resulting from the reflected IR radiation is related directly to the concentration of atmo spheric gases that can absorb the emitted IR radiation Before we can evaluate the cause of the bad global warming we must look at historical data on concentrations of greenhouse gases IR active gases in the atmosphere In the 1950s the U S government initiated a project to collect baseline data on planet Earth One of the most important studies was to monitor the concentration of CO in a remote clean environment The site selected for this monitoring program was the observatory on Mauna Loa in Hawaii This site was selected for its location in the middle of the Pacific away from major pollution sources and for its high altitude about 14 000 feet Data from this monitoring program are shown in Figure 5 3 and are available from the LDEO Climate Data Catalog which is maintained by the International Research Institute at Columbia Uni versity http www ingrid ldgo columbia edu Data from 1958 to the year 2000 not shown consistently show an increase in atmospheric CO concentrations In addition for the first time we can actual
12. temperature 25 Total mass of Dieldrin in flask 725 ng Volume in Sherer impinger 300 mL Mass in each purge interval is in measured in nanograms Express your answer atm m mol Compare your answer to the value from a reference text or a value from the Internet 9 CLL LI6TO 9 9 807 0 8 69 708 L999 0 SYS 6 98 Scro 0L 6 69 5580 0 TSL STL c90 0 6IL EL 9 0 0 SYL 9L LL SLLCO O 799 9p e9 68510 0 TA 09 0 69 9 TA 00 2 TA PAJU Ie 1oju TA PAHU PAW say sep ur SSEW asing sse UI ssePY omg ursse oun eA1oju WIL LARW asing PS vq Z t d IS VL 47 DATA COLLECTION SHEET GLOBAL WARMING DETERMINING IF A GAS IS INFRARED ACTIVE Purpose learn to use an infrared spectrophotometer To determine if a gas is infrared active BACKGROUND Although global warming has drawn growing political attention in recent decades relatively few people understand its causes and implications Global warming has two faces one that benefits us and another that may cause serious environmental and economic damage to the planet Conditions on Earth would be very different without the greenhouse effect of atmospheric warming Natural atmospheric gases including carbon dioxi
13. 38 DETERMINATION OF HENRY S LAW CONSTANTS Linear Regression Rep 1 0 879t Rep2 o Linear Fit Ln in water 0 1 2 3 4 5 6 Time hours Figure 4 3 Linear transformation of data to obtain the depletion rate constant Dr 2 15 x 10 4 atm m mol which is in good agreement with literature values 2 19 x 10 4 to 5 48 x 1074 ACKNOWLEDGMENT I would like to thank Josh Wnuk Whitman College Class of 2003 for data collection and analysis REFERENCES Bamford A Ko and J E Baker Environ Sci Technol 36 20 4245 4252 2002 Charizopoulos E and E Papadopoulou Mourkidou Environ Sci Technol 33 14 2363 2368 1999 Cooter E J W T Hutzell W T Foreman and S Majewski Environ Sci Technol 36 21 4593 4599 2002 Harmon Fetcho J A L L McConnell C R Rice and J E Baker Environ Sci Technol 34 8 1462 1468 2000 Mackay D W Y Shiu and R P Sutherland Envion Sci Technol 13 3 333 337 1979 Mamontov A A Mamontova E A and E N Tarasova Environ Sci Technol 34 5 741 747 2000 Subhash S R E Honrath and J D W Kahl Environ Sci Technol 33 9 1509 1515 1999 Thurman E M and E Cromwell Environ Sci Technol 34 15 3079 3085 2000 IN THE LABORATORY 39 IN THE LABORATORY During the first laboratory period you will prepare your purge apparatus Sherer imp
14. ate and sulfate is shown in Figure 7 1 Your retention times may differ from those shown below but the elution order should be the same Adjust the elution times to have a total run time of less than 15 minutes FAAS Standards The cations in the synthetic water are Mg Na and K Unlike the IC solution preparation you must figure out how to make the calibration solutions Stock solution concentrations should be 1000 ppm mg L for each cation made from the dried and desiccated salts Standards should be made for each cation using the approximate solution concentrations shown in the list that follows Note that you will have to make serial dilutions of the 1000 mg L stock solution to obtain the concentration shown below using standard class A pipets The exact range and approximate concentrations of standards and detec tion limits may vary depending on the FAAS unit that you use You may have to lower or raise the standard concentrations e 1 ppm 5 ppm 10 ppm 15 ppm 20 ppm 25 ppm and 50 ppm e Mg 0 05 ppm 0 1 ppm 0 2 ppm 0 5 ppm 1 ppm 1 5 ppm and 2 ppm e Na 0 2 ppm 0 5 ppm 1 ppm 3 ppm 5 ppm 10 ppm and 12 ppm e K 0 5 ppm 1 ppm 2 ppm 3 ppm 4 ppm and 5 ppm Each element will be analyzed using FAAS to create a linear calibration curve for each cation The data can be analyzed using the linear least squares Excel sheet described in Chapter 2 You will be given a water sample by your instructor tha
15. avelengths and intensity of light coming from the surface of the Sun at 5900 K The upper dashed line represents the wavelengths and intensity of light as predicted by physicists for a blackbody residing at the temperature of the sun This line predicts fairly accurately the spectrum of wavelengths observed just outside the Earth s atmosphere by satellites represented by the upper solid line The remaining line the lower solid line shows the spectrum of wavelengths detected at the Earth s sea surface using similar satellites As you can see some of the intensity is reduced and a few of the wavelengths are removed completely by atmospheric gases The wavelengths in Figure 5 1 are given in micrometers with ultraviolet UV radiation between 0 and 0 3 on the x axis visible light from 0 3 to about 0 8 and near infrared IR from about 0 8 to the far right side of the plot As you see most of the solar radiation entering Earth s atmosphere is in the form of visible light and near IR radiation Next notice the difference between the UV radiation intensity outside the atmosphere and at sea level These wavelengths which cause damage to skin and other materials are removed in the stratosphere during the formation of ozone shown below diatomic oxygen absorbs these wavelengths splits into free oxygen 0 25 Y T T T T T T T t T T T T T T T T T T T T T T T T T T 0 20 4 t Solar Irradiation Curve Outside Atmosphe
16. chniques are beyond the scope of this manual In this laboratory experiment you will be using a separatory funnel extraction procedure to measure the concentration of chlorinated pesticides in a water sample This water sample is relatively pure and does not contain appreciable amounts of a second phase This technique has been used for decades to monitor the presence of pesticides in water samples THEORY If you consider only one contact time in the separatory funnel we can define a distribution ratio D which describes the equilibrium analyte concentration Corganic between the methylene chloride and the water phases D C methylene chloride C water The extraction efficiency is given by 100D V methylene amp V water REFERENCES 85 When D is greater than 100 which it is for most hydrophobic analytes a single equilibrium extraction will quantitatively extract virtually all of the analyte into the methylene chloride phase However as you will note during the experiment some of the methylene chloride will stick to the sides of the separatory funnel and not pass into the collection flask a 100 mL volumetric flask To achieve complete recovery of the methylene chloride as well as complete extraction you will extract the sample three times and combine the extractions in a 100 mL collection flask We can also estimate how many extractions are necessary to remove a specified quantity of th
17. dard IV 2 52 ppm 11 3 ppm NO and 12 06 ppm 5027 Make by a 2 100 dilution of chloride stock 1 100 dilution of nitrate stock and a 1 100 dilution of the 1206 ppm sulfate solution Fill to the 100 mL mark with deionized water Calibration Standard V 5 04 ppm 22 6 ppm NO and 24 12 ppm 5027 Make by a 4 100 dilution of chloride stock a 2 100 dilution of nitrate stock and a 2 100 dilution of the 1206 ppm sulfate solution Fill to the 100 mL mark with deionized water Calibration Standard VI 11 34 ppm 50 85 ppm NO and 54 45 ppm SOL Make by a 1 10 dilution of chloride stock a 0 5 10 dilution of nitrate stock using a 500 0 uL syringe and 0 5 10 dilution of the 1206 ppm sulfate solution using a 500 0 uL syringe Fill to the 100 mL mark with deionized water 78 DETERMINATION OF AN ION BALANCE FOR WATER SAMPLE 4 D e lt eo t 0 00060 mg L 0 0050 mg L 0 0060 mg L chloride nitrate sulfate 11 491 14 296 STOP START Figure 7 1 IC output for chloride nitrate and sulftate Each calibration standard solution should be filtered through a 0 45 um Whatman HPLC filter cartridge and injected into the ion chromatograph system twice Average peak areas should be taken based on the two injections and used to produce linear calibration graphs using the linear least squares Excel program described in Chapter 2 To aid in your analysis a typical ion chromatogram of chloride nitr
18. de and water vapor are responsible for adjusting and warming our planet s atmosphere to more livable conditions In fact there is one popular theory that the Earth is actually a living organism and that under normal conditions without human interference the Earth will maintain the life sustaining environment that it has acquired over the last 100 million years or so This theory is the Gaia hypothesis proposed by James Lovelock and there are several short books on the subject The bad side the anthropogenic side of global warming is still strongly debated between some politicians and scientists but it is generally well accepted among scientists that humans are contributing exponentially to the warming of the planet Unfortunately some governments and political parties side with the Environmental Laboratory Exercises for Instrumental Analysis and Environmental Chemistry By Frank M Dunnivant ISBN 0 471 48856 9 Copyright C 2004 John Wiley amp Sons Inc 49 50 GLOBAL WARMING DETERMINING IF A GAS IS INFRARED ACTIVE economists who often have little knowledge of the science behind the argument but are concerned primarily with constant economic growth rather than sustained growth This bad side to global warming has been studied for several decades and data from these studies is presented below First it is important to understand the nature of the light coming from our Sun to the Earth Figure 5 1 shows three representations of the w
19. e analyte for a series of extractions This effectiveness can be evaluated by having an estimate of D and calculating the amount of solute remaining in the aqueous phase water after n extractions where Vwater i Cy Cy id Vorganic zs e ACKNOWLEDGMENT I would like to thank Josh Wnuk for the experimental design data collection and analysis REFERENCES Fifield F W and P J Haines Environmental Analytical Chemistry 2nd ed Blackwell Science London 2000 Perez Bendito D and S Rubio Environmental Analytical Chemistry Elsevier New York 2001 86 CONCENTRATION OF CHLORINATED PESTICIDES IN WATER SAMPLES IN THE LABORATORY Your laboratory procedure involves the extraction of very low concentrations of chlorinated pesticide PCB in water You will accomplish this by performing three extractions in a separatory funnel combining these extracts and concentrating the extract for analysis on a GC Finally you will analyze your samples on a capillary column GC equipped with an electron capture detector Safety Precautions Safety glasses must be worn at all times during this laboratory experiment Most if not all of the compounds that you will use are carcinogens Your instructor will prepare the aqueous solution of these compounds so that you will not be handling high concentrations The purge solution you will be given contains ppb levels and is relatively safe You should still use caution when usin
20. e atmosphere at the time the snow fell on the Earth An example of these data for the Vostok ice core is shown in Figure 5 4 This data set goes back in time 160 000 years from left to right from the present and gives us a long term idea of the composition of the atmosphere The three figures show the concentration of CH with time Fig 5 4a the concentration of CO with time Fig 5 45 and the estimated temperature with time Fig 5 4c The CH4 and CO data are self explanatory and are simply the gases trapped in the glacier but the temperature data are a bit more complicated To estimate the temperature as a function of time scientists look at the abundance of the oxygen 18 isotope in glacial water Water on Earth contains mostly oxygen 16 but a small amount of oxygen 18 is present During warmer geologic times on Earth more water containing is evaporated from the oceans and falls as snow over cold regions In contrast cooler geologic times will have less O in the atmospheric and snow By conducting experiments we can estimate how much is present at a given temperature and estimate what the temperature was when each layer of the glacial water was deposited This allows Figure 5 4c to be created When the three figures are compared a strong correlation between high CH concentrations high CO concentrations and high temperature is noticed This can be understood by 750 Cc oc 600 CH Concentration ppmv
21. ee metal THEORY When the concentration of all ions in solution is known it is relatively easy to calculate an ion balance An example is shown in Table 7 1 for a river water TABLE 7 1 Example Calculation of the Electroneutrality of a Hypothetical River Water Sample Molar Concentration Total Ion mol L Charge Balance Ion Balance Cations 3 8 x 107 7 6 x 107 34 x 1074 6 8 x 107 Na 2 7 x 107 2 7 x 10 4 Kt 5 9 x 1075 5 9 x 10 Total cations 1 77 x 1073 Anions HCO 9 6 x 10 4 9 6 x 10 4 22 x 1074 2 2 x 1074 5 3 x 10 6 5 3 x 1076 SO 1 2 x 107 2 4 x 1074 NO 3 4 x 1074 3 4 x 10 4 Total anions 1 77 x 10 Net difference 0 00 x 10 3 Source Adapted from Baird 1995 REFERENCES 75 sample In the data analysis for this laboratory report you must first convert from mg L to molar concentration Cations and anions in Table 7 1 are separated into two columns and each molar ion concentration is multiplied by the charge on the ion For calcium the molar concentration of 3 8 x 1074 is multiplied by 2 because calcium has a 2 charge The molar charges are summarized and if all of the predominant ions have been accounted for the difference between the cations and anions should be small typically less than a few percent of the total concentration A sample calculation is included in the Advanced Study Assignment Note that an important step in going from your analyses to your final ion bala
22. elp of American owned companies continue to produce and use these chemicals on a routine basis Chlorinated hydrocarbons can be detected at incredibly low concentrations by a gas chromatograph detector the electron capture detector ECD developed by James Lovelock also the originator of the Gaia hypothesis described in the background section of Chapter 5 In fact the first version of this detector was so sensitive that the company reviewing Lovelock s proposal did not believe his results and rejected his findings Lovelock persisted and today is responsible for one of the most important and most sensitive GC detectors The ECD can detect less than a picogram of a chlorinated compound But with this sensitive detection Environmental Laboratory Exercises for Instrumental Analysis and Environmental Chemistry By Frank M Dunnivant ISBN 0 471 48856 9 Copyright 2004 John Wiley amp Sons Inc 83 84 CONCENTRATION OF CHLORINATED PESTICIDES IN WATER SAMPLES limit comes a dilemma How sensitive should our environmental monitoring be Although the wisdom behind this policy is questionable we set many exposure limits for pesticides based on how little of it we can measure with our expensive instruments As we develop better and better instruments we push the detection limits lower and consequently we set our exposure limits lower Given the long term presence of these compounds we seem to be chasing a never ending lowering of the exposure
23. ernal standard 7 Cap the vial and allow it to stand for 5 minutes 8 Analyze each sample on the GC Waste Disposal All extraction solvents calibration standards and liquid waste should be collected in an organic waste container and disposed of by your chemistry stockroom Your sample tubes can be disposed of in the broken glass container 68 MONITORING THE PRESENCE OF HYDROCARBONS IN AIR ASSIGNMENT 1 Calculate the concentration of each analyte in an extract and the total mass of each analyte in your extraction vial 2 Use the flow rate and sample period to convert the total mass collected to the average concentration in the air ug m or ng m 3 Does your dose exceed the limit mentioned in the background material ADVANCED STUDY ASSIGNMENT 69 ADVANCED STUDY ASSIGNMENT 1 Draw and label a basic capillary column gas chromatograph 2 Describe each major component in one to three sentences DATA COLLECTION SHEET 3 EXPERIMENTS FOR WATER SAMPLES DETERMINATION OF AN ION BALANCE FOR A WATER SAMPLE Purpose determine the ion balance of a water sample and learn to perform the associated calculations To learn the use of flame atomic absorption spectroscopy unit To learn the use of an ion chromatograph unit BACKGROUND A favorite cartoon from my childhood shows Bugs Bunny preparing water fro
24. g these solutions since the pesticides and PCBs are very volatile when placed in water Avoid breathing the vapors from this solution Most of the solvents used in this experiment are flammable Avoid their use near open flames Chemicals and Solutions Neat solutions of the following compounds will be used by your instructor to prepare the aqueous solution Lindane Aldrin 2 2 4 4 6 6 Hexachlorobiphenyl Dieldrin not added to the solution to be extracted but to be used as a analyte recovery check standard Endosulfan I not added to the purge solution but to be used as a GC internal standard You will need in addition 80 0 ppm solution of Endosulfan I 80 0 ppm solution of Dieldrin Solid NaCl ACS grade Anhydrous 804 dried at 104 C IN THE LABORATORY 87 Glassware For each student group e 1 L separatory funnel e 10cm by 2 0 cm drying column e 100 0 mL volumetric flask e Pasteur pipets e Two 5 10 uL microsyringes Send 2 1 22 414AHCR rr Sa Tie 2 4 git 1000 12 00 14 08 1608 270 20 FAM ORM WEN 3200 Figure 8 1 Standard chromatograph of pesticide mix GC ECD column HP 1
25. ich nation has the largest emissions 6 MONITORING THE PRESENCE OF HYDROCARBONS IN AIR AROUND GASOLINE STATIONS Purpose determine the exposure of citizens to gasoline vapors To learn to use a personal sampling pump To learn to analyze gasoline components on a gas chromatograph BACKGROUND Each day we are exposed to a variety of organic vapors Yet we experience perhaps the greatest level of exposure when we fill our automobiles with gasoline Gasoline contains a variety of alkanes alkenes and aromatics In California alone it has been estimated that 6 100 000 Ib of gasoline vapors per year are released into the atmosphere http www arb ca gov It is also interesting to note that at least 23 of the 1430 National Priorities List sites compiled by the U S Environmental Protection Agency contain automotive gasoline http www atsdr cdc gov Table 6 1 shows the approximate composition of unleaded gasoline You should note several carcinogens in this list The right hand column shows data on exposure limits http www bpdirect com the allowed concentrations shown are relatively high compared to some pollutant exposures but if you consider how often you or the gas station attendant are exposed to these vapors you may start to appreciate the problem and potential cancer risk Environmental Laboratory Exercises for Instrumental Analysis and Environmental Chemistry By Frank M Dunnivant ISBN 0 471 48856 9 Copyright C
26. in designing a sampling procedure is to determine how long to sample to trap enough vapors to analyze on the gas chromatograph Your instructor will specify how long you should sample but typically a 5 to 10 minute sample will suffice You will also be using decane as an internal standard for the GC Your instructor will review the use of this approach at the beginning of the laboratory REFERENCES http www arb ca gov accessed Oct 5 2003 http www atsdr cdc gov accessed Oct 5 2003 http www bpdirect com accessed Oct 5 2003 http www brownoil com accessed Oct 5 2003 http www cdc gov niosh homepage html accessed Oct 5 2003 64 MONITORING THE PRESENCE OF HYDROCARBONS IN AIR IN THE LABORATORY You will be divided into groups and sent to a local gasoline station to take samples Your instructor will have already contacted the owner of the station and asked for permission You may actually fill cars with gasoline or you may simply stand beside car owners or station attendants as they operate the pumps Next you will extract the samples and analyze them on the GC There are many compounds present in gasoline but we will only be analyzing selected com pounds Safety Precautions e Safety glasses must be worn when in the laboratory e of these vapors have exposure limits and many are carcinogens Avoid exposure to these vapors in the laboratory by working in fume hoods Your instructor may choose to use carbo
27. inger and during the following 24 hours take samples to determine the Henry s law constant for selected pesticides and PCBs Your samples Tenax resin tubes can be extracted as you take them or during the beginning of the next laboratory period In the second laboratory period you will analyze the sample extracts on the gas chromatograph and process your data Safety Precautions e Safety glasses must be worn at all times during this laboratory experiment e Most if not all of the compounds you will use are carcinogens Your instructor will prepare the aqueous solution of these compounds so that you will not be handling high concentrations The purge solution you will be given contains parts per billion ppb level concentrations and is relatively safe to work with You should still use caution when using these solutions since the pesticides and PCBs are very volatile when placed in water Avoid breathing the vapors from this solution Extracts of the Tenax tubes should be conducted in the hood since you will be using acetone and isooctane two highly flammable liquids Chemicals and Solutions Neat solutions of the following compounds will be used by your instructor to prepare your aqueous solution e 2 2 Dichlorobiphenyl e Lindane e 4 4 Dichlorobiphenyl e 2 2 6 6 Tetrachlorobiphenyl e Aldrin e 2 2 4 4 6 6 Hexachlorobiphenyl e 3 3 4 4 Tetrachlorobiphenyl Dieldrin 4 4 DDD dichlorodiphenyldichloroethane 4 4 DDT
28. later Clean the Tenax resin traps by passing at least 5 mL of pesticide grade acetone through it followed by 5 mL of pesticide grade isooctane Dry the tubes by placing them in the gas stream of the Sherer impinger with no analyte present You will need 14 tubes per Sherer impinger unless you desorb the tubes as you collect them If this is the case you need only two tubes but you must still dry the tubes between samples Tenax resin tubes should be wrapped and stored in aluminum foil 1 Set up the impinger as shown by your instructor and set the gas flow rate while the flask is filled with deionized water no analyte solution this will be a good time to purge the solvent from the Tenax purge tubes Leave the final tube on the setup 2 Leave the gas flow set as adjusted in step 1 but disassemble the apparatus and empty the flask Tenax Pasteur tube pipet Secondary lt ppt regulator Cu tubing and m set at 50 psi T connectors Tenax tube Fine Sherer metering impinger Y Tenax tube Ultrapure or He Tenax ll tube Figure 4 4 Multiple Sherer impinger setup 42 DETERMINATION OF HENRY S LAW CONSTANTS Hill the flask with 300 mL of analyte containing water Have a stopwatch or clock ready assemble the Sherer flask turn the ground glass joint tightly to ensure a seal and note the time This is t 0 Check the
29. limits Thus we often turn to toxicology studies to determine exactly what level of exposure 15 acceptable The determination of the solubility of a specific compound is a relatively straightforward process in pure distilled water and solubility values can be found in the literature But how relevant are these published values to real world samples Literature values are available for the maximum solubility of com pounds in water In general solubilities of hydrophobic compounds increase with temperature But if you take a lake water sample and measure the concentration of DDT is the DDT present only in the dissolved phase One highly complicating factor in solubility measurements is the presence of a second phase in natural water samples that is usually described as colloidal in nature Colloids can take the form of inorganic particles that are too small to filter from the sample or as natural organic matter NOM that is present in most water samples Hydrophobic pollutants in water greatly partition to these additional particles in water and result in an apparent increase in water solubility So if you measure the pesticide concentration of a water sample and your data indicate that you are above the water solubility the solution may not actually be supersaturated but rather may contain a second phase that contains additional analyte Scientists have developed ways to detect the presence of colloid and colloid bound pollutants but these te
30. ly see the Earth breath as indicated in the inset in Figure 5 3 In the summer when plant growth is highest in the northern hemisphere CO levels are at a minimum This is followed by fall when plant growth is subsiding and dying and levels start to increase The concentration reaches a maximum in winter followed by a decrease in spring as plants start growing again to repeat the cycle 370 Note Seasonal Fluctuations 360 350 340 330 CO Concentration ppm 320 310 OO OC xx OC QN t wt OF WON x ders Sepe Ope 0 30D De EDO Dem oc oq Cot o C CoD f cL 1 c o C cL oT GO UO GO CO C CO CO TF C CO UOS C303 V3 DS c3 3 v3 723 Year Figure 5 3 CO measurements from Mauna Loa Data from http ingrid ldgo columbia edu BACKGROUND 53 One problem with the data set from Mauna Loa is that it represents only a small snapshot in time with issues such as global warming we must look at long term geological time scales To do this scientists have collected ice cores from a variety of places across the Earth Ice cores represent a long history of atmo spheric data As snow falls over cold areas and accumulates as snow packs and glaciers it encapsulates tiny amounts of atmospheric gases with it When ice cores are taken and analyzed carefully they can give information on the composition of th
31. m two flasks one containing H ions and another containing ions Although this is correct in theory only Bugs could have a flask containing individual ions In reality counterions must be present For example in highly acidic solutions the H ions are in high concentration but must be balanced with base ions usually chloride nitrate or sulfate In high pH solutions the OH ions are balanced by cations such as Na or Ca The combined charge balance of the anions and cations must add up to zero in every solution This is the principle behind the laboratory exercise presented here You will analyze a water solution for anions by ion chromatography IC and for cations by flame atomic absorption spectro scopy FAAS and use these data to determine the ion balance of your solution Of course this exercise is easier than in real life where you would have no idea which ions are present and you would have to analyze for every possible cation and anion In this exercise we tell you which anions and cations are present Environmental Laboratory Exercises for Instrumental Analysis and Environmental Chemistry By Frank M Dunnivant ISBN 0 471 48856 9 Copyright C 2004 John Wiley amp Sons Inc 73 74 DETERMINATION OF AN ION BALANCE FOR WATER SAMPLE The presence of a variety of cations and anions in solution is very important to organisms living in or consuming the water For example we could not live by drinking distilled o
32. n disulfide a highly toxic and cancer causing agent Always work in the fume hood with this solvent even when filling the syringe for injection into the GC Chemicals and Solutions We will analyze for the compounds shown in Table 6 2 Decane will be used as the internal standard that will be added to your desorption extraction solvent pentane or carbon disulfide as well as the GC calibration standards at a concentration of 29 2 ppm You will use the density to calculate the concentration in your calibration standards volume added times density equals mass added to volumetric Use the data shown in Table 6 3 to prepare your GC calibration standards if these standards are not provided from the stockroom The solvent used for your samples and standards will be pentane or carbon disulfide containing the same concentration of decane as used in the calibration standards You will also need approximately 50 mL of internal standard solution for extraction of your samples from the charcoal Your instructor may also have this solution prepared TABLE 6 2 Density of Compounds to Be Used in Calibration Standards Density Density Compound g mL or mg mL Compound g mL or mg mL Benzene 0 8787 m Xylene 0 8684 Ethyl benzene 0 866 o Xylene 0 8801 n Heptane 0 684 Isooctane 0 6919 Decane 0 73 internal standard Toluene 0 866 pue sprepuejs ur 6 eures ou oq p nous oue oq suonemuoeouoo
33. nce number is to account for all dilutions that you made in the lab REFERENCES Baird C Environmental Chemistry W H Freeman New York 1995 Berner E K and R A Berner Global Environment Water Air and Geochemical Cycles Prentice Hall Upper Saddle River NJ 1996 Dionex DX 300 Instrument Manual 76 DETERMINATION OF AN ION BALANCE FOR WATER SAMPLE IN THE LABORATORY Safety Precautions e As in all laboratory exercises safety glasses must be worn at all times e Use concentrated HNO in the fume hood and avoid breathing its vapor For contact rinse your hands and or flush your eyes for several minutes Seek immediate medical advice for eye contact Glassware e Standard laboratory glassware class A volumetric flasks and pipets Chemicals and Solutions e ACS or reagent grade NaCl KCl MgSO4 and Ca NO3 salts should be dried in an oven at 104 C and stored in a desiccator e 1 HNO for making metal standards e Deionized water e 0 2 um Whatman HPLC filter cartridges e 0 2 um nylon filters Following are examples of preparation of IC regenerate solutions and eluents consult the user s manual for specific compositions IC Regenerate Solution 0 025 N 5 4 Prepare by combining 1 00 mL of concentrated H2SO4 with 1 00 L of deionized water The composition of this solution will vary depending on your instrument Consult the user s manual IC Eluent 1 7 mM NaHCO 1 8mM Na CO Prepare
34. nd calculate the HLC for all the compounds in your samples 44 DETERMINATION OF HENRY S LAW CONSTANTS Response Signal STD3 DAECD1BJCH 1 556407 1 5e407 1 456407 140407 1 356407 1 36407 1 256407 1 20407 1 156407 1 16407 1 056407 1 07 9500000 9000000 8500000 8000000 7500000 7000000 6500000 6000000 5500000 5000000 4500000 4000000 3500000 3000000 2500000 Dolshin ODD 2 2 4 4 6 6 HCB 2 2 4 4 TCB Munic Yellow 2000000 7 Time 2 00 4 00 6 00 8 00 10 00 12 00 14 00 16 0018 00 20 00 22 0024 00 26 0028 00 30 00 32 00 Figure 4 5 Output from the GC Waste Disposal The water remaining in your Sherer impinger has been purged of all analytes and can be disposed of down the drain Your sample extracts must be treated as hazardous waste since they contain acetone isooctane and chlorinated hydro carbons These should be placed in a glass storage container and disposed of in accordance with federal guidelines ASSIGNMENT 45 ASSIGNMENT 1 Turn in a diagram of your purge setup 2 Turn in a spreadsheet showing the HLC calculation 3 Compare the HLC values calculated to values from the literature 46 DETERMINATION OF HENRY S LAW CONSTANTS ADVANCED STUDY ASSIGNMENT Iz 2 Draw and describe each major component of a basic capillary column gas chromatograph Calculate the Henry s law constant with the data set in Table 4 2 for Dieldrin Purge gas flow rate 0 500 L min System
35. oq Jey NON ur sprepuejs sojKpeue jo suoneuoouo 9 e qe ur UMOYS ou FN 767 767 767 TOT 767 O9FT SOE 0 80t 0L vOC SE C091 80tO L OSE 09 1 S00 tt os ouo Ax o CLV 69 95177 895711 TLY69 9 Lt 8 O LT 0 85169 9 CE LI 8069 ZELI EEr os ouonjo TSE SS 9L9 LT 8 8 I 669 9L9L C 8 8 I S66 vt os 2112005 CL YS 9 LC 89 I 0 95 5 89 1 THE 0 euvidog u 87 69 vO t ZELI 8069 ZELI EEr os ouozuog Aug 96C 0L 8tI c vLCLI 96501 8rIC wdd 5 1 os u zu g uoma 01 5 ueur 5 T JOA Tur 6c TW SZ punoduio rd 08 1 Oc Os 1 08 1 Sur sse WON TH pis PIS PIs TPS I pis 42015 Spunoduro eng spiepuejs ZUEN suonngos 6 9 FIAVL 65 66 MONITORING THE PRESENCE OF HYDROCARBONS IN AIR TABLE 6 4 Approximate Retention Times for Analytes on a DB 1 Column Retention Time Retention Time Analyte min Analyte min Benzene 4 52 Toluene 8 05 Ethyl Benzene 10 67 m Xylene 10 88 n Heptane 6 33 o Xylene 11 43 Isooctane 5 95 GC Conditions e Splitless for the first 2 minutes split mode for the reminder of the analysis e Injector temperature 250 C e Detector temperature 310 C e Oven Initial temp 40 C Hold for 5 minutes Ramp at
36. phere is heated by IR radiation incoming from the Sun rather than reradiated from Earth s surface To fully understand the importance of these gases in global warming we must also look at the type of radiation the Earth is emitting As visible light reaches Earth s surface it is absorbed by the surface and transformed into heat This heat is reemitted back into the atmosphere and space by Earth When physicists estimate the wavelengths and intensity of wavelengths for Earth as a blackbody at 320 K the dashed line spectrum shown in Figure 5 2 results Note that the wavelengths released by Earth are much longer wavelength far far to the right of the wavelengths shown in Figure 5 1 These far infrared T A J T T T T T T T NO M 320K 7 EAM J 150F uo o atm J 5 It window X 4 EN J 100f MAE 4 S NS o x 5 50r CH J L HO 0 C 1 W 400 600 800 1000 1200 1400 1500 Wavenumber T T T T 25 15 10 7 5 Wavelength um Figure 5 2 Wavelengths and intensity of wavelengths of radiation emitted by the Earth From Hanel et al 1972 52 GLOBAL WARMING DETERMINING IF A GAS IS INFRARED ACTIVE wavelengths are very susceptible to being absorbed by atmospheric gases as indicated by the decrease in intensity shown by the solid line The solid line shows the wavelength and intensity of wavelengths measured by a satellite above Earth
37. r deionized water alone We need many of the ions in water to maintain our blood pressure and the ion balance in our cells This need for ions in solution is important even for microorganisms living in water since water is their medium of life In distilled water microbial cells try to balance the ionic strength between the internal cell and external water In doing so in distilled water the microbe cell will expand and could rupture due to the increased volume of water required to balance the osmotic pressure across the cell membrane Another important point concerning ionic strength is the toxicity of inorganic pollutants specifically metals and nonmetals In general the predominant toxic form of inorganic pollutants is their hydrated free ion However notable excep tions to this rule include organic forms of mercury and the arsenic anion Inorganic pollutants are also less toxic in high ionic strength high ion contain ing waters due to binding and association of the pollutant with counterions in solution This is called complexation and is the focus of computer models such as Mineql Mineql and Geochem For example consider the toxicity of the cadmium metal The most toxic form is the 2 ion but when this ion is dissolved in water containing chloride a significant portion of the cadmium will be present as a much less toxic form of cadmium Similar relationships occur when other anions are present to associate with the fr
38. ration of lower concentration sulfate standards Thus the working stock solution concentrations of the anions are e 126 ppm e 1172 ppm NO e 1206 ppm 504 IC standards are made from the stock solutions by dilutions using 100 mL volumetric flasks and the appropriate pipets Each calibration level shown below contains all three anions in one 100 mL volumetric flask Final solutions should be stored in plastic bottles to prevent deterioration of the standards Calibration Standard I 0 063 ppm 0 565 ppm NO and 0 603 ppm 504 Make 0 05 100 dilution of chloride stock and nitrate stock using a 50 0 or 100 0 uL syringe and 100 mL volumetric flask Make a 0 05 100 dilution of the 1206 ppm sulfate solution using 50 0 or 100 0 uL syringe and fill to the 100 mL mark with deionized water Calibration Standard 0 252 ppm 1 13 ppm NO and 1 21 ppm 504 Make 0 2 100 dilution of chloride stock using 500 0 uL syringe 0 1 100 dilution of nitrate stock using a 250 0 uL syringe and 0 1 100 dilution of the 1206 ppm sulfate solution using 100 0 uL syringe Fill to the 100 mL mark with deionized water Calibration Standard 1 26 ppm 5 65 ppm NO and 6 03 ppm SOL Make by a 1 100 dilution of chloride stock a 0 5 100 dilution of nitrate stock using a 500 0 uL syringe and a 0 5 100 1206 ppm sulfate solution using a 500 0 uL syringe Fill to the 100 mL mark with deionized water Calibration Stan
39. re z 0 15 L Solar Irradiation Curve at Sea Level CES eo Curve for Blackbody at 5900 K I i gt 2 0 HO 8 5 iP D 2 i im 0 05 r 4 O di H20 H20 z e ts 0 1 1 L L L L L 1 L L 1 L L 1 1 L 0 0 2 0 4 0 6 0 8 1 0 1 2 1 4 1 6 1 8 2 0 22 2 4 2 6 2 8 3 0 32 Wavelength um Figure 5 1 Wavelengths and intensity of wavelengths of radiation emitted by the sun and reaching Earth s sea surface From Department of the Air Force 1964 BACKGROUND 51 radicals and binds to another to form O3 This is the source of concern with chlorofluorohydrocarbons which interfere with this process and promote the destruction of thus allowing more high energy UV to reach Earth s surface O g hv 202 g O g O2 g M Os g M g heat Visible light is also attenuated significantly by Earth s atmosphere but not to the extent that it limits the growth of plant life Some of the visible light is simply absorbed and rereleased as heat in the atmosphere Other visible wavelengths are scattered and reflected back into space which is why the astronauts can see the Earth from space Several compounds in the atmosphere partially or completely absorb wavelengths in the near IR radiation on the left side of the figure Absorption of these wavelengths is represented by the shaded areas for Os H20 and CO This is one mechanism of global warming in which the atmos
40. t contains each of the cations and anions mentioned above You must determine the concentrations of each ion Alternatively the cations can be analyzed by IC Consult the user s manual for specific details PROCEDURE 79 PROCEDURE Limits of the Method These will vary depending on the instrument you use Anions e 0 0001 ppm e 0 01 ppm 504 e 0 002 ppm NO Cations e 0 4 ppm Ca e 0 02 ppm Mg e 0 002 ppm Na e 0 1 ppm K This laboratory exercise will take three 4 hour laboratory periods if you are asked to perform all experiments Alternatively your professor may divide you into three groups an IC group a Ca and Mg group and a Na and K group If you are divided into groups the entire exercise can be completed in one lab period but you will be sharing your results with the remainder of the class IC Analysis 1 First sign in the logbook turn on the IC and start the system This will allow the eluent column and detector to equilibrate while you prepare your calibration standards 2 Prepare your calibration standards as described above 3 Dilute your water sample 1 500 1 250 1 100 and 1 1 for analysis and in step 4 analyze each sample from low to high concentration until you determine the appropriate dilution to be analyzed Analyze each water sample twice as time permits and determine the most appropriate sample dilution based on your calibration curve again from step 4 4 Analyze your IC standards
41. te the direction of the stretch Figure 5 6a is the normal way we think about with each carbon oxygen bond stretching in unison and away from the central carbon atom and no dipole present in the molecule However the stretches in Figure 5 6 and d are also possible and result in a temporary dipole that can absorb IR radiation Similar observations can be made for methane Figure 5 7 The symmetrical orientation is shown in Figure 5 7a while asymmetrical molecules are shown in Figure 5 6b and c which contain temporary dipoles The latter two molecules absorb IR radiation and result in a heating of the atmosphere H H H H C H Y b Figure 5 7 Molecular vibrations for methane REFERENCES 57 ACKNOWLEDGMENT I would like to thank Dr Paul Buckley for taking the IR readings given in the instructor s version of this manual REFERENCES Barnola J M D Raynaud S Korotkevich and C Lorius Nature 329 408 414 1987 Berner E K and R A Berner Global Environment Water Air and Geochemical Cycles Prentice Hall Upper Saddle River NJ 1996 p 32 Department of the Air Force Handbook of Geophysics and Space Environmental 1965 p 16 2 Genthon C J M Barnola D Raynaud C Lorius J Jouzel N I Barkov Y S Korotkevich and V M Kotlyakov Nature 329 414 418 1987 Hanel R A B J Conrath V G Kunde C Prabhakara I Re
42. ure limit for toluene is 100 ppm Data in this paragraph were obtained from http www brownoil com As you can see from the discussion above exposure to gasoline vapors although routine should be of concern to anyone filling his or her automobile s gas tank THEORY The sampling of gasoline vapors is a relatively easy process Figure 6 1 shows a typical sampling pump and sample cartridge The pump comes calibrated from the factory with respect to airflow and the flow can be adjusted on most pumps The pump pulls the air and vapors through the sampling tube thus avoiding both contamination of the sample tube with compounds from the pump and contam ination of the sampling pump with gasoline vapors A variety of sample tubes are available with difference resins designed for efficient adsorbance of analytes of REFERENCES 63 Figure 6 1 Q Max personal sampling pump Supelco Inc interest The tube you will use is filled with fine grained charcoal Each tube contains two compartments of resin The large compartment is at the end where the vapors are drawn into the system The air then passes through a smaller compartment which is analyzed separately to see whether vapors have saturated the first compartment of resin and passed to the second compartment When this saturation occurs it is referred to as breakthrough and the sample is not usable since you do not know if vapor has also passed the second tube The only difficult task
43. vah V V Salomonson and J Wolfrod Geophys Res 77 15 2629 2641 1972 Houghton J T F J Jenkins and J J Ephraums eds Climate Change The IPCC Scientific Assessment Cambridge University Press Cambridge 1990 Houghton J T L G Meira Filho B A Callander N Harris A Katterberg and K Maskell eds Climate Change The Science of Climate Change The IPCC Scientific Assessment Cambridge University Press Cambridge 1995 Jager J and F L Ferguson eds Climate Change Science Impacts and Policy Proceedings of the 2nd World Climate Conference Cambridge University Press Cambridge 1991 Jouzel J C Lorius J R Petit C Genthon N I Barkov V M Kotlyakov and V M Petrov Nature 329 403 408 1987 Keeling C D T P Whorf M Wahlen and J van der Plicht Nature 375 666 670 1995 Keeling C D J F S Chine and T P Whorf Nature 382 146 149 1996 LDEO Climate Data Catalog maintained by International Research Institute IRI at Columbia University http www ingrid ldgo columbia edu Mintzer I M ed Stockholm Environmental Institute Confronting Climate Change Risks Implications and Responses Cambridge University Press Cambridge 1992 Skoog D A F J Holler and T A Nieman eds Principles of Instrumental Analysis 5th ed Saunder College Publishing Philadelphia 1998 World Resources Institute World Resources 1996 1997 Oxford Universit
44. ve prepared for you Endosulfan I will act as an internal standard for the gas chromatographic GC analysis Seal the vial and shake it vigorously for 30 seconds Allow the layers to separate transfer 1 to 2 mL of the top isooctane layer into a autoinjection vial and seal it PROCEDURE 43 13 Add your name to the GC logbook and analyze the samples using the 14 15 following GC conditions 1 0 uL injection Inlet temperature 270 Column HP 1 cross linked methyl silicone gum 30 0 m length by 530 um diameter by 2 65 um film thickness 4 02 psi column backpressure 3 0 mL min He flow 31 cm s average linear velocity Oven Hold at 180 C for 1 0 minute Ramp at 5 0 C min Hold at 265 C for 16 0 minutes Total time 34 0 minutes Detector Electron capture detector Temperature 275 Makeup gas with 1 to 5 CH4 Total flow 60 mL min A sample chromatogram is shown in Figure 4 5 Calibration standards will be supplied by your instructor and will range in concentrations from 1 00 to 500 ppb Approximate retention times for the given GC setting are as follows Analyte Elution Time min Analyte Elution Time min 2 2 DCB 9 63 Endosulfan I IS 19 75 Lindane 12 13 Dieldrin 20 95 4 4 DCB 12 71 DDD 22 20 2 2 6 6 TCB 13 82 DDT 24 72 Aldrin 16 86 Methoxychlor 28 33 2 2 4 4 6 6 TCB 18 86 Sign out of the GC logbook and note any problems you had with the instrument Analyze the data a
45. y Press Oxford 1996 58 GLOBAL WARMING DETERMINING IF A GAS IS INFRARED ACTIVE IN THE LABORATORY There is no exact procedure for conducting this laboratory other than consulting the users guide for your IR instrument Sign in the instrument logbook and remember to record any problems with the instrument when you finish You will be provided with a variety of gases that you will measure on your IR instrument Print out the spectrum for each gas and use the resources in your library to determine what type of vibration is occurring at each wave number where you observe absorption of IR radiation Safety Precautions e Avoid the use of methane or other flammable gases around electronic equipment or flames Chemicals e Gases a CFC a CFC substitute and CH4 Equipment e IR spectrophotometer e IR gas cell Waste Disposal The gas cells should be filled and emptied in a fume hood ASSIGNMENT 59 ASSIGNMENT Turn in your IR spectrum and label each peak with respect to the vibration that is occurring 60 GLOBAL WARMING DETERMINING IF A GAS IS INFRARED ACTIVE ADVANCED STUDY ASSIGNMENT 1 What are the requirements for a gas to be IR active 2 Look up the composition of Earth s atmosphere Which gases would you expect to be IR active 3 Draw a diagram of a basic IR instrument and explain how it works 4 Using the Internet find how much is emitted each year by the most productive nations Wh
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