Anal. Chem. 1980, 5 2 , 1833-1836
traces of pyrene and fluoranthene or t h a t none were detected at the detection limit of their method. These results indicate t h e need for improvement of routine monitoring capabilities and for interlaboratory comparison data for trace level PAHs, many of which may be the most ecologically important of the fossil fuel hydrocarbons.
ACKNOWLEDGMENT T h e following laboratories and scientists participated with N B S in t h e intercomparison study: Andrew Benson, University of California, San Diego: Paul Boehm, Energy Resources Company, IT. (ERCO); J o h n Farrington, Woods Hole Oceanographic Institution; William MacLeod, NOAA, National Analytical Facility, Seattle; Patrick Parker, University of Texas; Robert Riley, Battelle-Pacific Northwest Laboratories; a n d David Shaw, University of Alaska. S u p p l e m e n t a r y Material Available: Tables IV and \.' containing data for the amounts of individual hydrocarbons in the Alaskan and Santa Barbara mussel homogenates, respectively, and Table VI containing the most abundant aromatic hydrocarbons ( 5 pages) will appear following these pages in the microfilrri edition of this volume of the journal. Photocopies of the supplementary material from this paper or microfiche (105 X 148 mm, 24X reduction, negatives) may be obtained from Business Operations, Books and Journals Division, American Chemical Society, 1155 16th St., N.W., Washington, D.C. 20036. Full bibliographic citation (journal, title of article, author) and prepayment, check or money order for $5.50 for photocopy ($7.00 foreign) or $3.00 for microfiche ($4.00 foreign), are required.
LITERATURE CITED (1) Chesier. S. N.; Gump, B. H.; Hertz, H. S.; May, W. E.; Wise, S. A. Ana/. Chem. 1978, 50, 805-810.
(3) 14)
(5j (6) (7) (8)
(9) (10)
(1 1) (12) (13j (14) (15) (16)
1833
Mediros, G. C.; Farrington, J. W. "Marine Pollution Monitoring (Petroleum)", Natl. Bur. Stand. (U.S.), Spec. Pub/. 1974, 409, 167-169. Warner, J. S. Anal. Chem. 1976, 48 578-583. Shaw, D. G.; Baker, B. A. Environ. Sci. Techno/.1978, 12, 1200-1205. MacLeod. W. D.; Brown, D. W.; Jenkins, R. G.; Ramos, S.L.; Henry, V. D. NOAA Technical Memorandum ERL. MESA-8 1976, 52 pp. DiSalvo, L. H.; Guard, H. E.; Hunter, L. .Environ. Sci. Technoi. 1975, 9 , -347-351 . . -- . . Goldberg, E. D.; Bowen, V. T.; Farrington, J. W.; Harvey, G.; Martin, J. H.; Parker, P. L.; Rlsebrough, R . W.; Robertson, W.; Schneider, E.; Gamble, E. Environ. Conserv. 1978, .5, 101-125. Farrington. J. W.; Teal, J. M.; Medeiror;, G. C.; Burns, K . A,; Robinson, E. A.; Quinn, J. G., Jr.; Wade, T. L. Anal. Chem. 1976, 48, 1711-1716. Hilpert, L. R.; May, W. E.; Wise, S. A.; Chesler, S. N.; Hertz, H. S. Anal. Chem. 1978, 50, 458-463. Wise, S. A.; Chesler, S. N.; Hertz, H. !3.; May, W. E.; Guenther, F. R.; Hilpert, L. R. "Proceedings of the International Congress on Analytical Techniaues in Environmental Chemistry"; Peraamon Press, New York. 1980; pp 41-52. Farrington, J. W.; Meyer, P. A. "Specialist Periodical Reports in Environmental Chemistry"; The Chemical Society: London; pp 109- 136. Dunn. B. P. fnviron. Sci. Techno/. 1976. 10. 1018-1021. Lee, R. F.; Sauerheber, R.; Benson, A. A. Science 1972, 177, 344-346. Dunn, B. P.; Stich, H. F. Proc. Soc. fxptl. Bid. Med. 1975, 150,49-51. Dunn, B. P . ; Young, D. R. Mar. Pollut. Bull. 1976, 7 , 231-234. Pancirov, R. J.; Brown, R. A. fnviron. Sci. Techno/.1977, 7 1 , 989-992.
RECEIVED for review December 26, 1979. Accepted June 11, 1980. The authors acknowledge partial financial support from the Bureau of Land Management through an interagency agreement with t h e National Oceanic and Atmospheric Administration, under which a multi-year program responding to needs of petroleum development in the Alaskan continental shelf is managed by the Outer Continental Shelf Environmental Assessment Program (OCSEAP) Office. Identification of any commercial product does not imply recommendation or endorsement by the National Bureau of Standards, nor does it imply t h a t t h e material or equipment identified is necessarily t h e best available for the purpose.
Determination of N-Nitrosamines from Diesel Engine Crankcase Emissions E. Ulku Goff," James R. Coombs, and David H. Fine New England Institute for Life Sciences, 125 Second A venue, Waltham, Massachusetts
02 154
Thomas M. Baines Environmental Protection Agency, 2565 Plymouth Road, Ann Arbor, Michigan 48 105
An artifact-free method for the analysis of nitrosamines in diesel engine crankcase emissions was developed. The method involved trapping volatile nitrosamines in either a pH 4 phosphate-citrate buffer solution or ThermoSorb/N cartridge, followed by extraction of the traps with appropriate solvents, concentration, and analysis of the concentrate on a gas chromatograph and/or high-pressure liquid chromatograph interfaced to a TEA Analyzer. Validation of the reliability of the method included the intentional addltlon of amines and/or nitrogen oxides. Confirmation of the i d e n t i of the nitrosamines was by high-resolution mass spectrometry. Detection limlts, based on a 60-L sample, were 0.1 pg/m3 for N-nitrosodimethylamine and 0.16 pg/m3 for N-nitrosomorpholine,
Amine-type compounds are often present in lubricating oils as friction modifiers, metal deactivators, and corrosion and rust inhibitors ( I ) . Oxides of nitrogen (NO,) are generated in situ during the combustion process in the cylinder head. Since N-nitrosation of amines via oxides of nitrogen has been shown t o be rapid, especially in nonaqueous solvents ( 2 ) . nitrosamines are to be considered likely contaminants in diesel 0003-2700/80/0352-1833$01 OO/O
engine crankcase emissions. Although N-nitrosodimethylamine (NDMA) has not been observed in automobile exhaust, it has been detected in Colorado's Eisenhower Road Tunnel ( 3 ) . Previous research on diesel engine crankcase emissions as a source of nitrosamine emissions has been inconclusive. In a recent study, NDMA was detected by using a gas chromatograph ((32)interfaced t o a nitrogen-selective Hall detect or; confirmation of the finding by GC-mass spectrometry (MS) was complicated by coeluting compounds ( 3 ) . An ana1,ysis of Tedlar bags containing diesel crankcase emissions did not indicate t h a t NDMA was present (3). When positive results were obtained, little effort was addressed to the possibility t h a t t h e nitrosamines were being formed as analytical artifacts, either during trapping or during analysis. In this work we developed analytical methods for volatile nitrosamines which were sensitive at the 0.1 wg/m3 level for NDMA and also demonstrated t h a t the methods were artifact free.
EXPERIMENTAL SECTION Materials. Organic solvents (Distilled in Glass) were obtained from Burdick and Jackson (Muskegon. MI). Morpholine (MOR) (Reagent ACS), pyrrolidine (PYR) (practical),piperidine (PIP) C 1980 American Chemical Society
1834
ANALYTICAL CHEMISTRY, VOL. 52, NO. 12, OCTOBER 1980 Sulfamic Acid Cartridge
Sample
>I
ThemoqarblS
Cartridge
Figure 2. T"er713Sorb Cartridee
'Y
Sample collection from crankcase emissions: sampling time, 0.5-1 h; flow rate, 2 L/min
Figure 1.
(practical), and dipropylamine (DPA) (practical) were obtained from Eastman Kodak Co. (Rochester, NY). Dimethylamine (DMA) (40% Aldrich analyzed) was obtained from Aldrich Chemical Co. (Milwaukee, WI). Standard nitrosamine solutions and ThermoSorb/N cartridges were obtained from the Analytical Services Laboratory of Thermo Electron Corp. (Waltham, MA). The pH 4 phosphate-citrate buffer, sulfamic acid (certified), and sodium sulfate (anhydrous, certified ACS) were obtained from Fisher Scientific Corp. (Fair Lawn, NJ). Gas mixtures of NO + NOPprepared in NPwere obtained from Scientific Gas Products (South Plainfield, NJ). The GC packing material, 10% Carbowax 20M, 0.5% KOH on Chromosorb WHP, 80-100, was obtained from Analabs, Inc. (North Haven, CT). A p p a r a t u s . The gas chromatography (GC) analyses were carried out with a Therm0 Electron GC-661 interfaced to a TEA-502 TEA Analyzer (Thermo Electron Corp., Waltham, MA). The GC column was packed with 10% Carbowax 20M and 0.5% KOH on Chromosorb WHP, 80-100 in a 2 mm 0.d. X 4 m long stainless steel tube. NDMA analyses were carried out a t 110 "C; the other volatile nitrosamines were analyzed a t 175 OC. The high-pressure liquid chromatograph (HPLC) analyses were carried out with a Varian 8500 LC pump (Varian Instrument Division, Palo Alto, CA) interfaced to a TEA-502 analyzer. The liquid chromatography (LC) column was a p-Porasil l o p (3.9 mm X 300 mm) column (Waters Associates, Milford, MA), used with a solvent system that contained 4-8% acetone in isooctane. The LC injector was a Model U6K (Waters Associates). Bendix Mesa C-115 air pumps (Bendix Corp., Rochester, NY) were used for sample collection. Air flow rates of the pumps were calibrated against a Hastings ALL 10L mass flow meter (Teledyne Hastings-Raydist, Hampton, VA). The method development and validation for crankcase emission analyses were carried out with a Mack ENDT 676 engine located at Thermo Electron Corp. The nitrosamine measurements of crankcase emissions were made on Mack ETAY(B) 670A, Detroit Diesel 6V-71N, and Caterpillar 3406 heavy duty diesel engines and a Mercedes Benz 240D light duty diesel vehicle. The engines and vehicles were tested a t Southwest Research Institute, San Antonio, TX. P r o c e d u r e . T r a p p i n g Techniques. The following two trapping techniques were developed: (1)dry traps consisting of a ThermoSorb/N cartridge in series with a sulfamic acid cartridge and (2) a liquid trap consisting of a phosphate citrate buffer a t p H 4 in a glass impinger tube. Emissions from the engines were collected by using a toggle valve (i.d. 3.9 mm) or manual rotary valve (i.d. 3.9 mm) situated on the road-draft tube connector housing on the engine valve cover. The valve and the traps were connected by 0.34.6 m of Teflon tubing (0.d. 3.9 mm; i.d. 2 mm). The sample collection apparatus is illustrated in Figure 1. The sampling was carried out for 0.5-1 h with a pump air flow of about 2 L/min. Precise time and flow data were used to compute sample collection volume. TherrnoSorblN Cartridge i n Series with a Sulfamic Acid Cartridge. According to the supplier, ThermoSorb/N cartridges were developed for artifact-free collection of N-nitrosamines from ambient air ( 4 ) ;for sampling diesel engine crankcase emissions, the relatively high oxides of nitrogen (NO,) levels necessitated placing a sulfamic acid cartridge in front of the ThermoSorb/N cartridge. Sulfamic acid reacts with the incoming amines, thus preventing possible artifactual nitrosation on the ThermoSorb/N
Extraction of nitrosamines from ThermoSorbIN cartridge:
(1) 10 mL of pentane wash from B to A; (2) 2 mL 5/95 dichloromethanelpentane wash from B to A; (3) dry the cartridge by blowing carrier gas through it; (4) 1.5-2 mL of acetone wash from A to B
a t high NO, levels ( 5 ) . At the end of the sampling period, the ThermoSorb/N and sulfamic acid cartridges were removed as a unit and separated. The ThermoSorb/N cartridge was washed t o remove nonpolar oily materials by reverse elution (see Figure 2) with 10 mL of pentane followed by 2 mL of a mixture of dichloromethane and pentane (5/95). The cartridge was then dried by blowing argon gas through it. The N-nitrosamines were finally eluted from the cartridge with 1.5-2.0 mL of acetone. A 10-25-pL aliquot of the acetone fraction was introduced in the GC-TEA or HPLC-TEA. Phosphate-Citrate p H 4 B u f f e r Traps. These traps consisted of two glass impingers (240 X 30 mm) in series, each containing 40 mL of a phosphate-citrate solution buffered at pH 4 together with 0.5-1 g of sulfamic acid. The traps were immersed in an ice bath to obtain better retention of nitrosamines. The sulfamic acid was used because it inhibits nitrosation (6)by competing with amines for the nitrosating agent. At the end of the sampling time, the trap contents were transferred to separatory funnels and extracted with 2 x 10 mL of pentane to remove the nonpolar oily materials from the aqueous phase. The pentane fraction was discarded. The trap contents were then extracted with 3 X 10 mL of dichloromethane (DCM), which contained the nitrosamines. The DCM fraction was dried over sodium sulfate and then concentrated on a Kuderna Danish evaporator to 1 mL. A 10-25 yL aliquot of the DCM concentrate was introduced into GC-TEA and/or HPLC-TEA for analysis. Artifact Control Experiments. A series of experiments were carried out to ensure that if nitrosamines were detected, they were present in the engine crankcase emissions a t the calculated amounts and were not being formed during sampling and/or analysis. Tests with Phosphate-Citrate Aqueous Traps. Recovery studies were carried out by adding 500 ng each of NDMA, Nnitrosodiethylamine (NDEA),N-nitrosodipropylamine (NDPA), N-nitrosodibutylamine (NDBA), N-nitrosopiperidine (NPIP), N-nitrosopyrrolidine (NPYR),and N-nitrosomorpholine (NMOR) to the traps and passing 200 L of air through the traps a t a flow rate of 2 L/min. The recovery efficiency for NDPA and NDBA was inadequate (see Table I), and the liquid traps were thus judged to be unusable for these two nitrosamines. For the two nitrosamines of interest, NDMA and NMOR, however, the recovery was 77 and 82%, respectively. The overall efficiency of the aqueous buffered traps was tested by introducing nitrosamines into the incoming air stream prior to two traps (in series). In all cases, 96% of the recovered nitrosamines were found in the first trap. The secondary amine precursors (MOR and DMA) of the two nitrosamines actually found to be present in crankcase emissions (NMOR and NDMA) were added (50 pg each) to an aqueous trap operated in parallel with a control trap. Even during sampling from a test engine, excess NMOR and NDMA were not found in the trap with added amines. In one case, an additional 14 mg of NO and 1 mg of NO2 gas mixture (100 ppm NO and 7 ppm NOz in the gas stream) were also introduced into one of the parallel sample lines over the course of sampline time. In no case was there any detectable nitrosation of the added amine (detection limit per trap was 0.007 pg for NDMA and 0.011 pg for NMOR). The Teflon tubing connecting the crankcase to the traps was checked for the artifactual formation of nitrosamines. During engine sampling two liquid traps were operated in parallel by using different lengths of tubing between the crankcase and traps (0.3
ANALYTICAL CHEMISTRY, VOL 52, NO 12, OCTOBER 1980
Table I. Extraction Efficiency of Various Nitrosamines ( 5 0 0 ng each) from pH 4 Phospate-Citrate Buffer Traps (40 m L ) recovery,” nitrosamine
%
recovery,Q nitrosamine
%
NDMA 17 NPIP 66 NDEA 66 NPYR 88 NDPA~ 9 NMOR 82 NDBA~ N.D.C (I The recovery is the average of two measurements. These nitrosamines were extracted into the pentane layer. N o t detected. Table 11. Recoveries of Various Nitrosamines ( 5 0 0 ng Each) from Sulfamic Acid and TherinoSorb/K Cartridges rC recoveryY
nitrosamine
a
ThermoSorb/N
empty cartridge and ThermoSorb/N
NDMA 77 NDEA 78 NDPA 79 NDBA 75 NPIP 81 NPYR 86 NMOR 83 Recovery is the average of two
sulfamic acidand ThermoSorbJN
57 61 55 51 56 44 54 42 58 53 55 57 53 58 measurements.
m vs. 2 m). There was no change in the levels of NDMA or NMOR with the longer sampling line. Checking for the formation of nitrosamines in the first few centimeters of sampling line was deemed unnecessary since heavy duty diesel engines normally release emissions through 0.6-1 m of road-draft tube. The identity of NDMA and NMOR from the liquid traps was established by equal quantitation a t the appropriate chromatographic retention time on both GC and HPLC-TEA. Further confirmation was obtained by combining the trap extracts from a single engine, concentrating to 1 mL, and examining the concentrate by GC-high-resolution MS, using peak matching (7). At the appropriate GC retention time, a molecular ion fitting the exact mass of NDMA was observed (resolution 9000). Quantitation by GC-TEA was also identical to quantitation by GChigh-resolution MS. Tests with ThermoSorblN and Sulfamic Acid Cartridges. As with the aqueous traps, recovery studies were conducted by using a mixture containing 500 ng each of NDMA, NDEA, NDPA, NDBA, NPIP. NPYR, and NMOR. These seDarate exDeriments were conducted first with the ThermoSorb/N-alone, second with an empty cartridge followed by a ThermoSorb/N cartridge, and third with a cartridge filled with sulfamic acid followed by a ThermoSorb/N cartridge. The results, shown in Table 11, show that despite the pentane and DCM/pentane wash, 77-86% of the nitrosamines of interest are recovered in the acetone fraction. By comparison, if acetone alone had hen wed, the recovery would have been 98-100% ( 4 ) . The “dead space” in an empty cartridge
led to another 20-30% loss in recoLery. Recovery with and without sulfamic acid in the cartridge was virtually identical (see Table 11). Fifty micrograms each of DMA and MOR were added to a sulfamic acid-Thermosorb,” cartridge system and operated in parallel with control cartridges. In one experiment an additional 5.4 mg of NO and 0.4 mg of NO2gas (80 ppm NO and 6 ppm NOz in the gas stream were also introduced into one of the parallel sampling lines. In every case, the traps with the added amine or amine plus NO and NO2 contained the same NDMA and NMOR levels (if any) as in the control cartridges. The detection limit per cartridge system was 0.007 for NDMA and 0.011 pg for NMOR. ThermoSorb/N cartridges have been tested for breakthrough, using the seven test nitrosamines ( 4 ) . Even after passing 2000 L of air at 2 L/min and 25 “C through the cartridges, breakthrough was not observed. RESULTS AND DISCUSSION Using the analytical methods described here, we measured the emissions from t h e crankcases of three heavy duty and one light duty diesel engines. For t h e three heavy duty engines, the nitrosamine levels reported in Table I11 were composited over seven operating modes, using a modification of the EPA’s 13-mode Federal test procedure weighing method. According t o the modification, nitrosamine amounts were cornposited by taking 12% of first mode, 16% of second mode, 12% of third mode, 20% of fourth mode, 12% of fifth mode, 16% of sixth mode, and 12% of seventh mode nitrosamine amounts. For t h e light d u t y engine, t h e nitrosamine levels were averaged over two modes, 20 m p h and 50 m p h steadystate operation NDMA was found t o be present with four different lubricating oils in four different engines. Typical NDMA emissions varied from 4.4 to 136 ~ g / h .NMOR was found to be present in only two of t h e engines, with three of the lubricating oils. NMOR emissions were less t h a n for NDMA, with the largest emission being 12 pg/h. Sampling was generally carried out with the sulfamic acid-Thermosorb,” cartridges in parallel with the aqueous trap buffered at p H 4. Quantitation between t h e two traps was the same, within experimental t,> n o r . T h e identity of NDMA and NMOR was confirmed by obtaining similar quantitation a t the appropriate chromatographic retention time on both GC-TEA and HPLC-TEA. Further identification was obtained from GC-high-resolution MS evidence on samples for each engine. ACKNOWLEDGMENT We are very grateful to Karl Springer of Southwest Research Institute (Emissions Research Department) for use of their engine test facility and operation of the engines. We thank E d Doyle and J i m Barton of Thermo Electron Corp. for valuable assistance. We also thank our co-workers a t the New England Institute for Life Sciences for their valuable discussions and support.
Table 111. N-Nitrosamine Levels in the Crankcase Emissions of Four Diesel Engines seven-mode composite NDMA diesel engine
lubricating oil
1 1 1 1 2 3
1 2 3
46 Not detected.
4 4 4 4 Light weight
ah3
1835
Hg/h pg/m3 0.5 4.4 N.D.Q 3.7 58.4 0.1 12.3 89.6 1.1 1.4 17.2 136 3.7 11.0 N.D. 4.2 35.8 0.2 3.8 6.8 N.D. vehicle-data are the arithmatic average of two modes.
NMOR llgth N.D.“ 0.8 10.8 11.8 N.D. 2.0 N.D.
Anal. Chem. 1980, 52, 1836-1841
1836
LITERATURE CITED (1) Schilling, G. J.: Bright, G. S. Lubrication 1977, 63, 2, 13. (2) Challis, B. C.; Kyrtopoulos, S. A. J . Chem. SOC.,Perkin Trans 7 1979, 299. (3) Hare. C. T.; Montalvo, D. A. Diesel Crankcase Emissions Characterization, EPA Contract No. 68-03-2196: Ann Arbor, MI, 1977. (4) Rounbehler, D. p.; Reisch, J. w.; Coombs, J. R.; Fine, D. H. Anal. Chem. *a70 me.“,
69
I C ,
91-
L,”.
(5) Goff, E. U., unpublished data.
(6) Douglas, M. L.; Kabacoff, B. L.; Anderson, G.A. J . SOC.Cosmet. Chem. 1978, 29, 581-606 (7) Gough, T. A.; Webb, K. S.; Pringuer, M. A.: Wood, B. J. J . Agric. Food Chem. 1977, 25. 663.
RECEIVED for review May 22, 1980. Accepted July 7, 1980. This work was supported by the U S . Environmental Protection Agency under Contract No. 68-03-2719.
Volatile Environmental Pollutants in Biological Matrices with a Headspace Purge Technique Larry C. Michael,* Mitchell
D. Erickson,
Sandra P. Parks,’ and Edo D. Pellizzari
Chemistry and Life Sciences Group, Research Triangle Institute, P.O. Box 12 194, Research Triangle Park, North Carolina 27709
Gas stripping and dynamic headspace anatysis were evaluated as methods for purging volatile halogenated organics from human biological samples (urine, blood, milk, and adipose tissue). I n gas stripping, volatile compounds are purged by bubbling an inert gas through a liquid sample at elevated temperature. The purged organic materials are trapped on the polymeric sorbent Tenax GC for subsequent gas chromatographic analysis. In dynamic headspace analysis, the gas passes over rather than through the solution. This procedure is particularly applicable to samples which foam, such as biological samples. Validation experiments involved recovery studies on fortified samples by both gas chromatography and mass balance experiments with I4C-labeled compounds. Recoveries were generally 60-95 % The procedure was developed to accommodate a high sample throughput by using a simple apparatus and was intended for purging of the sample followed by analysis of the Tenax GC cartridge by thermal desorption/gas chromatography/mass spectrometry/computer.
.
Investigation of volatile organic compounds in human tissues has received recent attention due to the occurrence of such compounds in t h e environment (1-3). Many of these compounds, particularly halogenated species, are known or suspected carcinogens, and an assessment of body burden is essential to an understanding of their potential health effects. A number of techniques developed for t h e determination of volatile organic compounds in water, particularly drinking water, were considered for application to human tissue samples. T h e methods fall into six basic categories: (1)solution purge (gas stripping) (4-6); (2) dynamic headspace purge ( 7 , 8); (3) solvent extraction (9, 1 0 ) ; (4) liquid-phase adsorption on polymeric sorbents (11-13); (5) direct aqueous injection (14-16); (6) static headspace analysis ( 1 7 , 1 8 ) . Solvent extraction, using high- or low-boiling solvents, generally suffers from poor efficiency even when multiple extractions are employed (19). Direct aqueous injection lacks adequate sensitivity for tissue analysis due to injection volume limitations and, in addition, would present large matrix interferences. Adsorption of volatile organics from a biological matrix directly Present Address: Northrop Environmental Technology Center, Research Triangle P a r k , NC 27709. 0003-2700/80/0352-1836$01 .OO/O
onto polymeric sorbents is highly susceptible to clogging which may result in significant flow alterations (20). Static headspace analysis requires knowledge of t h e equilibrium coefficients between gas and liquid phases, as well as rigid control of the sample temperature, headspace volume, and other parameters. In addition, except for compounds which strongly favor the gas phase (e.g., highly volatile, water-insoluble substances), static headspace analysis lacks sufficient sensitivity. In light of these difficulties, actual experimental investigations were performed only for gas stripping and dynamic headspace techniques in combination with vapor collection on Tenax GC. Gas stripping analysis involves bubbling an inert gas through the solution t o purge t h e volatile organic materials from the sample, followed by collection of the entrained vapor on a polymeric sorbent. This technique has been shown t o be extremely sensitive for water insoluble organics with boiling points less t h a n approximately 150 “C ( 2 1 ) . Dynamic headspace analysis is similar to gas stripping except the inert gas passes over, rather than through, t h e solution. T h e purpose of this research was t o develop and validate analytical procedures for determining volatile halogenated organic compounds in human blood, urine, milk, and adipose tissue. The approach to the problem involved complementary, parallel studies; (1)recovery studies with radiolabeled compounds and (2) recovery studies with nonradiolabeled substances. T h e experiments with radiolabeled compounds measured recoveries both as the percentage of fortified material detected on the sorbent cartridge and as the percentage remaining in the sample following gas stripping or dynamic headspace analysis. This experimental approach permitted construction of a “mass balance” for the entire procedure. Experiments with nonradiolabeled compounds provided recoveries of compounds with a broad range of volatilities t o permit quantitation of compounds detected in actual samples. T h e use of two independent validation procedures not only assures the precision and accuracy of the analytical results b u t also guards against systematic errors.
EXPERIMENTAL SECTION Apparatus. The apparatus used in gas stripping and dynamic headspace analyses are shown in Figure 1. Two biological media, blood and urine, were used for analytical method development. Gas stripping, because of its inherent sensitivity advantage, was studied first. The apparatus (Figure l A ) , consisted of a roundbottom flask containing a gas dispersion tube for purge gas inlet, a thermometer, and a Teflon-coated, magnetic stir bar. The flask was topped with a short glass tube containing a small plug of glass G 1980 American Chemical Society
