Environ. Sci. Technol. 1992, 26, 1533-1540
(34) Grosjean, D.; Williams, E. L., I1 Atmos. Environ. 1992,26A, 1395-1405.
(31) Pandie, S.; Paulson, S. E.; Seinfeld, J. H.; Flagan, R. C. Atmos. Environ. 1991,25A, 997-1008. (32) Grosjean, D., Seinfeld, J. H. Atmos. Environ. 1989, 23, 1601-1606. (33) Grosjean, D. J . Air Waste Manage. Assoc. 1990, 40, 1397-1402.
Received for review January 15, 1992. Revised manuscript received April 3, 1992. Accepted April 21, 1992. This work was supported by National Science Foundation Grant ATM-901)3186.
Enantioselective Determination of Chlordane Components Using Chiral High-Resolution Gas Chromatography-Mass Spectrometry with Application to Environmental Samples Hans-Rudolf Buser' and Markus D. Muller
Swiss Federal Research Station, CH-8820 Wadenswil, Switzerland Christoffer Rappe Institute of Environmental Chemistry, University of Umei, S-90187 Umei, Sweden
Technical chlordane was examined using both achiral and chiral high-resolution gas chromatography (HRGC) with detection by electron capture, negative ionization mass spectrometry (ECNI-MS). The enantiomer separation of several chiral octachlordanes including cis- and trans-chlordane was achieved and enantiomeric ratios of approximately 1:l were determined using a modified 8cyclodextrin as the chiral selector. The method was then applied to tissue extracts of several aquatic vertebrate species collected from the Baltic Sea (herring, salmon, and seal) and from Antarctica (penguin). The isomer profiles of the 6and nonachlordanes observed in the biological samples using achiral HRGC-MS differed from those observed in a technical chlordane mixture, with some minor components of the technical mixture showing much higher abundance in the aquatic samples. Chiral HRGC now showed enantiomeric ratios of several chiral octachlordanes differing from 1:l in each of these aquatic species. The changed enantiomeric compositions likely result from enantioselective biological processes and not from abiotic processes such as chemical, distribution, or transport processes in the environment. The results reinforce previous data showing the presence of these contaminants in biota from the most remote area on earth, Antarctica. 4
Introduction Chlordane is among the most prevalent and important toxic environmental contaminants. It was used as a pesticide for both residential and agricultural applications over several decades (1,2).By 1988, the use of chlordane has stopped in the United States, Japan, and most European countries, but consumption in other countries continues. The global occurrence of chlordane has been well documented, and nowadays chlordane or its metabolites are readily found at all trophic levels, in specimens from such remote areas as the Arctic and Antarctic. It is even present in human adipose tissue and milk (3-7). Residues found in biological and environmental samples include components from technical chlordane and their metabolites such as oxychlordane (8). Chlordane is now considered a possible human carcinogen (9). Technical chlordane is a complex mixture of various chemically similar components derived from hexachlorocyclopentadiene. Detailed analysis of the technical mixture revealed up to 120 components (2,10-12). However, in most of these reports the chirality of some of the chlordane 0013-936X/92/0926-1533$03.00/0
components, including those of the main constituen%. cisand trans-chlordane, has hardly ever been considcrdd. Enantiomers (optical isomers) of chiral compounds may show different biological behavior and properties such as uptake, metabolism, and excretion (13,15). Transformation reactions in biological systems and in the environment may thus show stereoselectivity (16-18). In contrast, abiotic processes such as chemical, distribution, or transport processes will be the same for both enantiomers, and enantiomeric composition will thus remain unchanged. h enantioselective determination of chiral compounde in environmental and biological samples may thus give additional information on possible degradation pathways a-ld may allow a distinction of enantioselective biotic from nonenantioselective abiotic processes. In this respect, however, only minor progress has been made because of the unavailability of analytical techniques, particularily so at the trace concentration levels required for environmental analyses. Recently, the enantiomer separations of cis- and tram-chlordane were reported using a high-resolution gas chromatography (HRGC) column coated with a pure Pcyclodextrin (P-CD) derivative (19). These columns, however, have some limitations for general use including low thermal stability and poor inertness. These deficiencies often lead to excessive retention times and high background signals, which preclude their use for trace environmental and biological applications. Recently, HRGC columns prepared by dilution of high-melting 0-CD derivatives in apolar polysiloxane stationary phases were described (20,21).These columns show somewhat reduced chiral selectivity, but are more suitable for chiral analyses of real biological samples. The enantioselective determination by use of this technology of a-HCH enantiomers in environmental samples was recently reported (18). We report here the first application of chiral HRGCmass spectrometry (MS) toward the enantioselective determination of chiral chlordane components in a technical product and in environmental biological samples. Various chlordane components were first assigned in a technical chlordane mixture using achiral HRGC-MS and then enantiomeric ratios of chiral components were determined using chiral HRGC-MS. The information thus obtained was then used to assign these components in aquatic vertebrate species from the Baltic Sea and from the Antarctic. Interestingly, several chiral chlordane compo-
0 1992 American Chemical Society
Environ. Sci. Technol., Vol. 26, No. 8, 1992
1533
nents showed a enantiomeric composition in these aquatic species different from those observed in a technical chlordane mixture. Experimental Section Sample Description. Herring oil and tissues of a salmon, a seal, and a penguin were examined. The herring oil was prepared from fresh herring (Clupea harengus) collected from the Gulf of Bothnia during June 1988. Preparation of the oil was performed at the Norwegian Herring Oil and Meal Industry Research Institute, Bergen, Norway, as previously described (22). The salmon muscle tissue was from a female salmon (Salmo salar) caught in the Ume river at Stornorrfors, Sweden, in 1989. The seal sample was a composite of liver tissue of adult grey seal (Halichoerus grypus) collected from the Baltic Sea along the Swedish southeastern coastline during the 1980s. Finally, the penguin tissue was a sample from a juvenile Adelaide penguin (Pygoscelis adelis) found dead at Shackleton's Hut, Ross Island, Antarctica, in March 1988. The frozen tissue was shipped to the University of Umel, Sweden, where extraction and cleanup were carried out. Sample Extraction and Cleanup. A sample preparation protocol previously described was followed (23). Briefly, the tissues (- 20 g) were homogenized with Na2S04 and extracted with dichloromethane/n-hexane (1:l). Lipid removal was effected by polyethylene film dialysis followed by gel permeation chromatography using Biobeads SX3. The eluate was then fractionated using Florisil chromatography. In this scheme, the chlordane components including oxychlordane were found to elute into fraction 2 (15% dichloromethane/n-hexane).Aliquots of 2 pL corresponding to 200-400 mg of tissue were used for analysis. Technical Chlordane Mixture. A sample of technical chlordane was obtained from Maag Ltd., Dielsdorf, Switzerland, in the 1950s. The sample had been archived in Wadenswil and was now used for comparative analyses. Solutions in toluene (1-10 ng/pL) were prepared and used for analysis. HRGC-MS Analysis. A VG Tribrid double-focusing magnetic sector hybrid mass spectrometer (VG Analytical Ltd., Manchester, England) was used for all mass spectrometric measurements. The ion source was operated in the electron capture, negative ionization mode (ECNI, 50 eV, 140 OC). A mixture of argon/lO% methane was used mbar, as measured by the ion as a buffer gas (1 X gauge). The use of this buffer gas mixture was recently described (24) and resulted in lowered hydrocarbon background ions and diminution of ions resulting from post electron capture processes, specifically of (M -C1 + H)anions formed in C1 atom displacement reactions. Some analyses of the technical chlordane were also carried out with electron ionization (EI, 70 eV, 180 "C). Full-scan mass spectra ( m / z 50-550,1.16 s/scan, resolution 500) were recorded for analyte identification in the technical chlordane mixture and in all environmental samples. Analyses were later repeated with selected-ion monitoring (SIM) for increased sensitivity and optimal enantiomer/isomer separation (faster cycle times). An ion descriptor (m/z 405.798,407.795,409.792,439.759,441.756, 443.753; 0.50 s/scan) monitored the CloH6C18-and CloH5C1< ions characteristic of the octa- and nonachlordanes. A lock mass of m / z 451.974 from perfluorotributylamine was used. Concentrations of octa- and nonachlordanes in the biological samples were estimated from SIM chromatograms in comparison to those of trans-chlordane and trans-nonachlor present in the technical mixture by assuming the same response for all isomers. The concentrations of trans-chlordane and trans-nonachlor in the 1534
Environ. Scl. Technol., Vol. 26, No. 8, 1992
technical mixture were estimated as 20 and 7% from an E1 total ion chromatogram and compared favorably with those listed for a similar product (11). The data thus generated are semiquantitative, and quantitation was not of prime concern in this study. All samples were comparatively analyzed using achiral and chiral HRGC column systems previously described (18, 21). The HRGC columns used were a 20-m PS086 glass capillary (0.32-mm id.; 0.2-wm film thickness) as the achiral column and a 20-m PS086 column with 10% permethylated heptakis(2,3,6-tri-O-methyl)-P-CD (PMCD; amount relative to PS086) added as the chiral selector. PSO86 is an OH-terminated methylpolysiloxane containing 15% phenyl groups with a polarity similar to SE54 and DB-5. Initially, an 25-m SE54 fused-silica column was also used. The achiral PS086 HRGC column was temperature programmed as follows: 100 OC, 2 min isothermal, 20 OC/min to 140 O C , then at 3 OC/min to 250 "C, followed by an isothermal hold at this temperature. The chiral PS086/10% PMCD HRGC column was operated at a lower intermediate temperature (120 "C) and a slower programming rate (2 OC/min) for increased enantiomer resolution. All samples (2 p L in toluene) were on-column injected at 100 OC. Data acquisition and retention time measurements were started at 140 (PS086) and 120 "C (PS086/10% PMCD), respectively. Compound Identification. No individual chlordane components were available as standards. This, however, caused no significant problems since all compounds of interest could be easily identified in the technical chlordane mixture and then assigned in the environmental samples using published retention data (retention indexes), in particular the data reported by Dearth and Hites (2). These identifications were done initially on the SE54 HRGC column, a column similar in polarity to the columns used in previous studies (2-4, 6, 25). The compounds considered here were cis- and trans-chlordane, cis- and trans-nonachlor, and components MC4, MC5, MC6, and MC7 (Miyazaki compounds, ref 25), K and U82 (2,6,26). Compound identification was supported from full-scan mass spectra (molecular ions, number of C1 atoms, and fragmentation patterns) and aided by taking into consideration the relative amounts of compounds reported in the technical chlordane mixtures (2,11). Attention should be given to the fact that octa- and nonachlordanes may interfere in each other's SIM chromatograms (M*-)due to the presence of (M + C1)- (chloride attachment) and (M - C1)- or (M - C1 + H)-, respectively, despite use of the above buffer gas. Results and Discussion Achiral and Chiral Components i n Technical Chlordane. Technical chlordane consists of a complex mixture of primarily hepta-, octa-, and nonachlorinated, tricyclic compounds. Technical chlordane is prepared by the Diels-Alder reaction of hexachlorocyclopentene and cyclopentadiene to chlordene, an unsaturated hexachlorinated, tricyclic compound (27). Further chlorination in a subsequent step leads to products containing two to three additional chlorines in the cyclopentane ring (octaand nonachlordanes; for structures, see Figure 1). These products are of the 6 2 and 6 + 3 substitution type (2). The main constituents in technical chlordane, cis- and trans-chlordane and trans-nonachlor, belong to these groups. The presence of lower chlorinated components in the starting material (e.g., pentachlorocyclopentadienes) will lead to additional components of the 5 + 2 and 5 + 3 substitution type. Furthermore, there are a number of
+
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Figwe 1. Smctures of eight octa- and ncmachlordanes identifled in a technical chlordane mixture and In environmental samples. The two enantiomers of transchlordane (arbiiarlly labeled as I and 11; mirror plane perpendicular through C2 and C,) are shown in the top row. Note that in the structures of components MC4 and MC7 the H and CI substltuents on C5 and C6 may be Interchanged (see ref 25).
Table I. Octachlordanes and Nonachlordanes Identified in Technical Chlordane and in the Environmental Samples compounda
structure, chirality
ret timeb (min)
former assignmente
MS datad 5+3 5+3 6+2 5+3 6+2 5+3 caged 6+3 6+3 6+3
1986 P44 2070 P57 ~ 5 8 2085 2101 P59 0.8 2118 P62 2.4 2158 P68 1.0 ~ 8 5 2272 0.0 2125 P64 2129 P65 2258 P83 "MC compounds refer to Miyazaki et al. (25),US2 to Dearth and Hites (2). *Retention time on 20-m PS086 achiral HRGC column (see Figure 2); for exact conditions, see text. cEnantiomer resolution (R values) observed on 20-m PS086/10% PMCD chiral HRGC column. Number of Cl's, molecular ions, and substitution type. 'Peak number and retention index (DB-5); see ref 2. U82 MC4 trans-chlordane MC5 cis-chlordane MC7 K MC6 (nonachlor 111) trans-nonachlor cis-nonachlor
not known Figure 1, chiral Figure 1, chiral Figure 1, chiral Figure 1, chiral Figure 1, chiral not shown, chiral Figure 1, chiral Figure 1, achiral Figure 1,achiral
17.75 19.67 20.05 20.75 20.95 21.68 25.41 20.22 20.82 25.17
enant resol ( R ) obsC
more complex structures present in the technical mixture, resulting from rearrangement reactions (e.g., WagnerMeerwein rearrangement), and we refer the reader to the studies by Dearth and Hites (2) and others for more detailed information. The structures of several compounds were elucidated by 'H- and 13C-NMRspectroscopy and X-ray crystallography (2, 11, 12,25,28-30). In Figure 1 we show the structures of octa- and nonachlordanes that were of particular interest in the present study. These compounds all have endo configuration. cis-Chlordane and trans-chlordane (the structures of the two enantiomers are shown in Figure 1, top row) and components MC4, MC5, MC6, MC7, and K (caged, structure not shown) are chiral; cis- and trans-nonachlors are achiral due to a symmetry plane through Cz and C8. Some minor components (MC4, MC5, and MC7) can be considered as dechloro homologues of nonachlors containing a pentachlorocyclopentene moiety. The structure and chirality of component U82 is not yet known. The synthesis of technical chlordane yields the chiral components in enantiomeric ratios of 1:1, since there are no chiral reaction partners involved in the synthesis.
0.5 1.0 1.3
Cls Cls Cls Cls Cls Cls Cls Clg Clg Clg
406 406 406 406 406 406 406 440 440 440
The identification of the chlordane components in our technical mixture was aided by the E1 and ECNI mass spectra. In ECNI, all chlordane components considered here show M - ions, but a rather nonspecific fragmentation to C10H5C13-(m/z 230), CI0H4Cl4-( m / z 264), CloH3C15(m/z 298), and CloHzC&-(m/z 332). The presence of C5C15-(m/z 235; retro Diels-Alder fragment ion) is indicative of a hexachlorocyclopentene moiety in the molecule such as from cis- and truns-chlordane and cis- and trans-nonachlor (2). A pentachlorocyclopentene moiety is indicated by the presence of C5HC14-(m/z 201) and the absence of C5C15-. The mass spectra thus give information on the substitution type (e.g., 6 2 versus 5 3) of such chlordane components (2). In Figure 2a,b ECNI SIM chromatograms (m/z410 and 444) show the elution of octa- and nonachlordanes in technical chlordane on the achiral PS086 HRGC column, respectively. As indicated, the major components, cis- and truns-chlordane and cis- and trans-nonachlor, are easily detected. The additional components assigned are U82 (also known as early chlordane, ref 2), MC4, MC5, MC7, K, and MC6 (also known as nonachlor 111, refs 2 and 26).
+
+
Envlron. Scl. Technot., Vot. 26, No. 8 , 1992 1535
Table 11. Enantiomeric Ratios (ER Values)" of Chiral Chlordane Components Observed in Technical Chlordane Mixture and Aquatic Vertebrate Species compound
technical chlordane
Baltic herring
Baltic salmon Baltic seal Antartic penguin MC4 0.95 f 0.05 0.7 f 0.05 0.7 f 0.05 2.7 f 0.1 2.2 f 0.1 trans-chlordane 1.01 f 0.01 0.42 f 0.02 1.19 f 0.02 0.60 f 0.04 b MC5 0.99 f 0.01 0.81 f 0.02 0.75 0.02 0.24 f 0.04 0.91 f 0.02 cis-chlordane 1.01 f 0.01 1.35 f 0.1 0.38 f 0.03 b, c b, c MC7 0.98 f 0.02 0.83 f 0.02 0.92 f 0.02 0.86 f 0.02 1.35 f 0.03 K 0.97 f 0.02 b b b b Enantiomeric ratios (ER values) defined as ER = p 1 / p 2 where , p1 is the peak area of earlier eluting enantiomer and p 2 is the peak area of later eluting enantiomer, using the m / z 410 ion. Ratios ER > 1 indicate predominance of earlier eluting enantiomer and ER < 1 indicate predominance of later eluting enantiomer. From an ER value the enantiomeric excess of an enantiomer can be calculated as EE (%) = 100 X (ER - l)/(ER + 1). Average and range from two replicate measurements reported. bER values were not determined because the quantities present were too low. Signal disturbed by coelution of trans-nonachlor.
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Flgure 2. ECNI SIM chromatograms showing elution of (a) octachlordanes (rn / z 4 10) and (b) nonachlordanes (rn / z 444) in the technical chlordane mixture, using the achiral PS086 HRGC column. Signal for trans-chlordane marked by asterisk in chromatogram b. Abbreviations: cC8 and tC8 for cis- and franschlordane, cN9 and tN9 for cis- and trans-nonachlor; for others, see text.
Figure 3. ECNI SIM chromatograms showing elution of (a) octachlordanes ( m / z 410) and (b) nonachlordanes ( m / z 444) in the technical chlordane mixture, using the chiral PS086/10% PMCD HRGC column. Note resolution of several octachiordanes into pairs of enantiomers. Signals for cls- and bans-nonachlor marked with asterisks in chromatogram a. Abbreviations: see Figure 2.
A few additional components (X,-X,) could not be as-
temperature (250 "C) was found to be favorable for sensitive ECNI measurements. The chromatograms in Figure 3a,b now show the separation of some chiral chlordane components into pairs of enantiomers. In particular, trans-chlordane, cis-chlordane, components MC4, MC5, MC7, and K are clearly separated into doublets. As expected cis-nonachlor and trans-nonachlor, both achiral, show single peaks (see Figure 3b). The chiral component MC6 apparently is not separated into enantiomers. Chiral separations are highly dependent on the actual site and conformation of the chiral centers ( 3 0 , and therefore, full separation cannot be expected for all pairs of enantiomers under the conditions chosen. The enantiomer resolutions ( R values) observed differed for the various chiral components and ranged from 0 (component MC6, not resolved) to 2.4 (component MC7, fully resolved (see Table I). Component U82 is seen to elute as a single peak. Presently it is unclear whether this compound is achiral or whether the two enantiomers are not resolved by PS086/10% PMCD. The enantiomers of heptachlor and heptachlor epoxide, two additional chiral components related to chlordane but not considered here, remained unresolved on our chiral HRGC system although separation has been shown by use of another system (19). As shown in Figure 3a, all the major chiral components of technical chlordane are in fact separated into pairs of enantiomers. Mass spectra of the isomers may show differences, but the mass spectra of enantiomers are identical. With minor deviations, this was in fact observed and is described below. In contrast to the situation with isomers including diastereomers, SIM responses of enantiomers are truly iden-
signed so far. Retention and MS data of the compounds assigned are listed in Table I. Several of these components were also detected in the environmental samples, as discussed below. Apparently, achiral HRGC successfully allows separation of cis- from trans-chlordane, and cisfrom trans-nonachlor, but it does not separate chiral components into pairs of enantiomers. Parts a and b of Figure 3 show ECNI SIM chromatograms (m/z 410 and 444) of technical chlordane analyzed on the chiral HRGC column. The mixed stationary phase (PSO86/lO% PMCD) shows a changed polarity compared to the pure polysiloxane, but the elution order of the octachlordanes remains similar, except that the elution order of cis-chlordane and component MC5 is now reversed. A problem one might conceivably encounter in chiral HRGC with mixtures containing several chiral isomers is coelution of the later eluting enantiomer of one isomer with the earlier eluting enantiomer of another isomer, although the isomers themselves may have been previously separated by achiral HRGC. This in fact was observed when the technical chlordane mixture was analyzed on a HRGC column containing 20% PMCD: although enantiomer separations generally increased, the changed polarity caused the second eluting enantiomer of trans-chlordane to coelute with the fiist eluting enantiomer of cis-chlordane (data not shown). Therefore, the best compromise between enantiomer and isomer separation was the PS086/10% PMCD column. This chiral HRGC column showed a chromatographic performance (separation efficiency, Trennzahl) similar to that of the achiral column. Furthermore, the low bleed level even at maximum operating 1536 Environ. Sci. Technol., Vol. 26, No. 8, 1992
Figure 5. ECNI mass spectrum of component U82 (early chlordane) Identified in penguin from Antarctica. C5HCI,- (mlz 201) indicative of 5 3 type substitution. Note presence of signals from coeluting SB
+
(s3-
Figure 4. ECNI SIM chromatograms showing elution of (a-d) octachlordanes (mlz 410) and e-h) nonachlordanes (mlz 444) on the achlral PS086 HRGC column in (a, e) Baltic hening, (b, f) Baltic salmon, (c, g) Baltic grey seal, and (d, h) Antarctic penguin. Abbreviations and asterisks: see Figures 2 and 3.
tical. Therefore, peak area ratios determined in SIM chromatograms are expected to reflect the true ratios of enantiomers in a given sample. In Table I1 we list the enantiomeric ratios (ER values) of some chiral components in the technical chlordane mixture. The ratios actually observed are close to the theoretical values of 1.00; the minor deviations are probably due to inaccuracies in our determinations, particularly in the case of small and incompletely resolved peaks. Enantiomeric ratios determined with our chiral HRGC column in another application (a-HCH in environmental samples) showed good reproducibility (1.3% standard deviation at 95% confidence interval; see ref 18). Chlordane in Environmental Biological Samples. In parts a-h of Figure 4 we show SIM chromatograms of biological environmental samples, analyzed on the achiral PS086 HRGC column. The extracts examined were of herring, salmon, and seal from the Baltic sea and of a penguin from the Antarctic. Chlordane components are detectable in all four samples. The compounds detected are components U82, MC4, MC5, MC6, and MC7, cis- and trans-chlordane, and cis- and truns-nonachlor as well as various minor components. Component K was not found to be present in these extracts. There are significant differences in the isomer profiles in these samples and that observed in the technical chlordane mixture; in some cases minor components of the technical mixture predominate in the aquatic samples, particularly in the warm-blooded species (seal and penguin). The combined levels of octaand nonachlordanes were estimated to be 5 (herring), 20 (salmon), 40 (seal), and 80 ng/g (penguin), and thus in the range of those previously reported for aquatic organisms (see ref 6 and citations therein).
- Se-).
The observed differences in isomer profiles apparently are due to a different accumulation behavior of these isomers in the various species. More than 100-fold differences in accumulation among chlordane components had been reported earlier (6). The differences in the isomer profiles can also be due to abiotic processes prior to exposure to a species. Chemical, distribution, transport, or other processes, particularly during long-range transport to such remote areas as the Antarctic, could change the relative amounts of chlordane components and hence the isomer profiles. However, all these abiotic processes are not expected to change the enantiomeric ratios. Whereas the isomer profiles of Baltic herring and salmon are very similar (see Figure 4a,b), those of the Baltic seal and the Antarctic penguin are clearly different (see Figure 4c,d). cis-Chlordane as the major and trans-chlordane as a further main octachlordane are present in both of the fish. These two main components of technical chlordane, however, are very minor components in the warm-blooded species (seal and penguin). Previously, cis-chlordane was reported as a main isomer in other fish, Arctic and Norwegian cod (4, IO),and both cis- and truns-chlordanes were reported absent in an Arctic mammal, polar bear (3). An apparently lower metabolism of chlordane components (as indicated by higher parent-to-metabolite ratios) in fish than in marine mammals has been pointed out (6). Of particular interest is the high accumulation of component U82 of unknown structure in Baltic grey seal (see Figure 4c) and component MC5 in Antarctic penguin (see Figure 4d). A higher accumulation of both compounds can be ascribed to their 5 + 3 substitution type structure. Compounds with three chlorines in the cyclopentane ring generally seem more resistant to metabolism and therefore more prone to accumulation in biological tissues (6). cis-Nonachlor and trans-nonachlor (6 + 3 substitution type) fall into this category and exhibit higher bioaccumulation than do the 6 2 type compounds. Of the samples analyzed here, nonachlors showed highest accumulation in the penguin (-70 ng/g). Component U82 corresponds to component U6 previously identified in marine mammals and showing high accumulation ( 3 , 4 ) . I t is reported as one of the most important compounds with the pentachlorocyclopentene moiety in technical chlordane (2). Component MC5 also showed a higher accumulation in man (6). ECNI mass spectra of the main chlordane components in the biological samples were in agreement with those from the technical chlordane mixture; ECNI sensitivity was high enough to allow the recording of full-scan mass spectra of all the major components in these biological samples. As an example, the mass spectrum of component U82 (5 + 3 type substitution) is shown in Figure 5. ECNI
+
Environ. Sci. Technol., Vol. 26, No. 8, 1992
1537
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