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Anal. Chem. 1986, 58, 2022-2029
1248, 12672-29-6; Arochlor 1254, 11097-69-1; Arochlor 1260. 11096-82-5;Arochlor 1262,37324-23-5;Arochlor 1268,11100-14-4.
LITERATURE CITED Gebhart. J. E.; Hayes, T. L.; Alford-Stevens, A. L.: Budde, W. L. Anal. Chem. 1985, 5 7 , 2458-2483. Slivon, L. E.; Gebhart, J. E.: Hayes, T. L.; Alford-Stevens, A. L.; Budde. W. L. Anal. Chem. 1985, 5 7 , 2464-2469. Webb, R. W.; McCall, A. C. J . Assoc. Off. Anal. Chem. 1972, 5 5 , 746-752. Webb, R. W.; McCall, A. C. J . Chromatogr. Sci. 1973, 1 1 , 366-373. Albro, P. W.; Haseman, J. K.: Clemmer, T. A,; Corbett, 6 . J. J . Chromatogr. 1977, 136, 147-153. Sawyer, L. D. J . Assoc. Off. Anal. Chem. 1978, 61, 272. Albro, P. W.; Parker, C. E. J . Chromatogr. 1979, 169, 161-166. Krupcik, J.; Leclercq. P. A.; Garaj, J.; Simova, A. J . Chromatogr. 1980, 791, 207-220. Albro, P. W.; Corbett, J. T.; Schroeder, J. L. J . Chromatoor. 1981. 205, 103-111. Mullin, M.; Sawka, G.; Safe, L.; McCrindle, S.:Safe, S. J . Anal. Toxicol. 1981, 5 , 138-142. Steichen, R. J.; Tucker, R. G.:Mechon, E. J . Chromatogr. 1982, 236, 113-128. Bagley, G. E.; Reichel, W. L.; Cromartie, E. J . Assoc. Off. Anal. Chem. 1970, 5 3 , 251-261.
(13) . . Stalling, D. L.; Huckins, J. N. J . Assoc. Off. Anal. Chem. 1971, 5 4 , 801-807. Elchelbecger, J. W.; Harris, L. E.; Budde, W. L. Anal. Chem. 1974, 46, 227-232. (151 Martelli. G. P.; Castelli, M. G.; Fanelli, R. 6iomed. Mass Specfrom. 1981, 8, 347-350. (16) Dunn, W. J., 111; Stalling, D. L.; Schwartz, T. R.; Hogan, J. W.: Petty, J. D.; Johansson, E.; Wold, S. Anal. Chem. 1984, 5 6 , 1306-1313. (17) Safe, S.;Hutzinger, 0. Nature (London) 1971, 232, 641. (18) Steichen, R. J.: Tucker, R. G.; Mechon, E. J . Chromatogr. 1982, 236, 113-126. (19) Picker, J. E.; Colby. B. N. Presented at the Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Atlantic City, NJ, March 11, 1983. (20) Schwartz, T. R.; Campbell, R. D.; Stalling, D. L.; Little, R. L.; Petty, J. D.; Hogan, J. W.: Kaiser, E. M. Anal. Chem. 1984, 5 6 , 1303-1308. l\ i.d. I)
RECEIVED for review November 21,1985. Accepted April 14, 1986. This article has not been subjected to review by the
U.S. Environmental Protection Agency. Therefore, it does not reflect the views ofthe Agency, and no official endorsement should be inferred.
Accuracy and Precision of Determinations of Chlorinated Pesticides and Polychlorinated Biphenyls with Automated Interpretation of Mass Spectrometric Data Ann L. Alford-Stevens,*Thomas A. Bellar, James W. Eichelberger, and William L. Budde Environmental Monitoring and Support Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, 26 West St. Clair Street, Cincinnati, Ohio 45268
Performance characteristicswere determined for an analytical method that includes automated interpretationof mass spectra of polychlorinated biphenyls (PCBs) and 21 chiorinated pesticides. Determination of PCBs was by level of chlorlnath. After three capl#ary cokmn h)ectkn techniques were evaluated, a spItWs8, cokl-trapphg techdque was used. ReproduclbMty of mass spectrometer response to calibration compounds relative to two internal standards was evaluated over a period of 3 months. I n the three sets of fortilied water extracts, the largest relative standard deviation of replicate measurements was 8.4% for indivkluai pestkkies (concentrations of 3-10 pg/L), 18% for PCB isomer groups (concentrations unknown), and 2.9% for total PCBs (concentrations of 27-130 pg/L). Method bias was calculated for each pesticide and for total PCB comentrations in each of fhe three data sets. The highest method bias was observed with river water extracts. The detection limit for each pesticide in reagent water is approxlmately 1 wg/L.
For almost 20 years since Jensen (1)discovered the presence of polychlorinated biphenyls (PCBs) in fish tissue, analysts have been concerned with identification and measurement of PCBs. Initially, PCBs were detected as spurious peaks in an electron capture (EC) detector chromatogram of sample extracts that also contained common chlorinated hydrocarbon pesticides (2). The retention times of the spurious peaks were not equivalent to those of the common pesticides. As early as 1967, Widmark reported identification of PCBs with a mass spectrometer (MS) detector (3). The very characteristics that led to the first identification of PCBs have continued to cause
problems for PCB analysts. The 125 individual PCBs encountered in Aroclor mixtures ( 4 ) are extracted with and frequently elute from a GC column arpong other chlorinated hydrocarbons. To minimize these potential interferences when EC detectors are used, numerous procedures have been devised to separate PCBs from coextracted sample components. Several of these were discussed by Hutzinger et al. in their book on PCBs (5). Unfortunately, these procedures frequently rely on separation of sample extracts into fractions that must be analyzed separately, thereby increasing the number and cost of analyses required to obtain needed information. Although the number of laboratories using MS detectors has increased dramatically during the past decade, the majority of analytical laboratories continute to rely on EC detectors for determinations of PCBs and chlorinated hydrocarbon pesticides (6). The main reason is that EC detectors are more sensitive to these analytes than MS detectors operated in electron ionization mode with full-range data acquisition. This difference in sensitivity has been reported (7) to be as much as 2 to 3 orders of magnitude. The EC detector, however, does not provide the molecular structure information that is obtained with an MS detector. That structural information increases the level of confidence that the component being measured has been correctly identified. Although PCBs have been included among analytes listed in official U.S. Environmental Protection Agency (USEPA) analytical methods using MS detectors (B), until recently PCBs have been determined as Aroclor formulations with USEPA methods. With USEPA Method 680, however, PCBs are identified and measured by level of chlorination (9). In addition to PCBs, that method lists 21 chlorinated hydrocarbon pesticides as method analytes. This report presents accuracy
This article not subject to U S . Copyrlght. Published 1986 by the American Chemical Society
ANALYTICAL CHEMISTRY, VOL. 58, NO. 9, AUGUST 1986
Table I. Calibration Solution Components and Quantitation Ions compound
quant ion
PCB Calibration Congeners4 2-C11-PCB(no. 1) 2,3-C12-PCB(no. 5) 2,4,5-ClyPCB (no. 29) 2,2',4,6-Cld-PCB (no. 50) 2,2',3,4,5'-C&-PCB (no. 87) 2,2',4,4',5,6'-C&-PCB (no. 154) 2,2',3,4',5,6,6'C1,-PCB (no. 188) 2.2'.3.3'.4.5'.6.6', . . Cln-PCB (no. 200) I
I
I
I
2,2',$3',4,4',5,5',6,6'-
Cllo-PCB(no. 209)
188 222 256
292 326 360 394 428
quant ion
4,4'-DDD 4,4'-DDE 4,4'-DDT dieldrin endosulfan I endosulfan I1 endosulfan sulfate endrin endrin aldehyde endrin ketone heptachlor heptachlor epoxide methoxychlor nonachlor, trans-
235 246
235 79 195 195 212
81 67 67 272 353 227
409
Internal Standards 500
Pesticide Analytes aldrin BHC (a,,!?, 6, and y isomers) chlordane (aand y isomers)
compound
iyi
chrysene-d12 phenanthrene-dlo
240 188
Surroeate . Comoounds y-BHC-l3C6 4,4'-DDT-13C12
187 241
373
"Cll0-PCB was used as the calibration congener for both C&and ClIo-PCBs;the quantitation ion for Cl,-PCBs was m / z 466.
and precision data obtained when Method 680 was used to determine P€Bs and the listed pesticides in water extracts analyzed with GC/MS procedures that include the use of special software for automated identification and measurement of analytes. Unprocessed GC/MS data were handled without human interaction with the software operating on a minicomputer that is an integral part of the GC/MS system. The PCB software, which has been described in detail in a previous report (IO),was expanded to obtain the pesticide data reported here.
EXPERIMENTAL SECTION Materials. All compounds used in this study were the highest purity materials available from commercial sourcm and were used without further purification. The nine individual PCB congeners (Table I) used as calibration congeners (11)were obtained from Ultra Scientific (Hope, RI). Chrysene-dlz and phenanthrene-dlo were obtained from Aldrich Chemical Co. (Milwaukee, WI). The Pesticides and Industrial Chemicals Repository, Environmental Monitoring Systems Laboratory, USEPA, Las Vegas, NV, provided 20 of the 21 nonisotopically labeled pesticides (Table I). The remaining pesticide, endrin aldehyde, and Aroclors 1221,1232, 1014,1242,1248,1254,1260,1262, and 1268 were obtained as 5 pgfrL methanol solutions (QuaiityAssurance Technical Materials, >95% purity) from the Repository for Toxic and Hazardous Materials, Environmental Monitoring and Support Laboratory, USEPA, Cincinnati, OH. The y-BHC-lSC6and the 4,4'-DDT-13C12 were obtained as solid materials from Cambridge Isotope Laboratories, (Woburn, MA). Reagent water was prepared by passing distilled water through a column containing about 450 g of granular activated carbon. Solutions. A 5 pg/lL single-component solution of each unlabeled compound obtained as a solid material was prepared by weighing and dissolving each in hexane. One hexane solution of 4,4'-DDT-l3Cl2 and y-BHC-13C12contained each component at a concentration of 1 pg/pL. Another hexane solution was prepared to provide 375 ng/pL of each of the deuterated compounds, chrysene-dl, and phenanthrene-dlo. A multicomponent hexane solution containing 250 ng/pL of each unlabeled pesticide except endrin aldehyde was prepared from the single-component solutions. Aliquots of this solution, the endrin aldehyde solution, and appropriate Aroclor solutions were mixed and diluted with methanol to provide the desired concentrations when 1 mL of
2023
the resulting solution was added to a 1-L water sample. A 1-mL aliquot of the 250 ng/pL multicomponent pesticide solution was diluted to 10 mL to provide a 25 ng/rL solution in hexane. The single-componentPCB congener solutions were mixed and diluted to prepare a solution that contained twice the amount of each PCB congener required for the highest concentration solution needed to calibrate MS response. Equal volumes of this PCB congener solution and the 25 ng/pL pesticide solution were mixed to prepare the highest concentration solution required for calibration, and the resulting solution was diluted as necessary to provide four additional calibration solutions. To each 1 mL of calibration solution was added 20 pL of the 375 ng/pL solution of chrysene-dlzand phenanthrene-dlo to produce a concentration of 1.5 ng/pL of each. Concentrations of the C11-C13 PCB calibration congeners were 0.5, 2.5,5, 10, and 25 ng/pL in solutions 1-5, respectively. These concentrations were doubled for each C14-C1, PCB congener, tripled for each C17-C18 PCB congener, and quintupled for Cllo PCB. Calibration solutions 1-5 contained 1,5,10,20,and 50 ngfpL, respectively, of each pesticide except endrin aldehyde (which was not present in solution 3), endosulfan sulfate, and endosulfans I and 11. Each of the latter three pesticides was present in all five solutions at double the concentration of other pesticides. Water Extracts. To each 1-L aliquot of each water sample in a 2-L separatory funnel was added (syringe delivery) 1 mL of the methanol solution containing unlabeled pesticides and Aroclor mixtures. When available,a 1-mLaliquot of the methanol solution containing the two isotopically labeled pesticides (4,4'-DDT-13C12 and y-BHC-13Cd also was added. After being shaken, the solution was allowed to stand for at least 1 h. Each 1-L fortified water sample was extracted (without pH adjustment) with three sequential 60-mL portions of methylene chloride. Each extract was dried by passing it through a column of purified anhydrous sodium sulfate and was concentrated to about 6 mL with a KudernaDanish apparatus. After solvent exchange to hexane, each extract was concentrated to a f i i volume of 1.0 mL, and a 20-pL aliquot of the solution containing 375 ng/rL of each of the internal standards (ISs, chrysene-dlz and phenanthrene-dlo) was added just before GCfMS analysis. With each set of extraction experiments, one 1-L portion of the appropriate water sample was extracted with all of the above conditions except that none of the solution containing Aroclors and unlabeled pesticides was added. River Water Samples. Ohio river water samples were collected from a boat dock approximately 10 river miles upstream from downtown Cincinnati, OH. Water was dipped from the river with a clean glass beaker and poured into a large glass carboy. After the carboy was returned to the laboratory, it was shaken until the water appeared to be homogeneous, and a 6-L separatory funnel was filled with homogenized water. After the separatory funnel was shaken, six 1-L aliquots were drained out. Five 1-L aliquots were fortified and extracted with the same procedures used for fortified reagent water, and the remaining 1-L aliquot was extracted and processed without fortification. GC Analytical Conditions. With splitless injections, two different initial column temperatures were used with the coldtrapping and solvent effect injection techniques described by Grob (12)to concentrate sample components in a short section of the injector end of the capillary column. The initial column temperature was 80 "C for splitless, cold-trapping injections and 45 "C for splitless, solvent-effect injections. A solvent-flush, hotneedle injection technique was used for all splitless injections. The needle was inserted into the injector (220 OC) with the vent valve open. Ten seconds after inserting the needle, the vent valve was closed. Five seconds after closing the vent valve, the 2-rL extractfsolution aliquot was injected during a 1-s period, and the temperature program was initiated. A solvent-flush, cold-needle injection technique was used for on-column injections. The needle was inserted into the injector with the GC oven cooled to
