Anal. Chem. 1981, 5 3 , 1351-1356
1351
Chromatographic-Spectrometric Identification of Airborne Polynuclear Aromatic Hydrocarbons Diiip R. Choudhury’’ and Brian Bush Division of Laboratories and Research, New York State Department of Health, Albany, New York 12201
An integrated approach comprising a combination of glass capillary gas chromatography (GC), mass spectrometry (MS), liquid chromatography (LC), and ultraviolet (UV) spectrometry has been used for unambiguous identification of polynuclear aromatic hydrocarbons (PAH) in airborne particulates. Liquid chromatography with on-line ultraviolet spectral scanning was particularly valuable for differentiation and positive identification of isomeric and coeluting PAHs. The advantages of this approach over GC/MS alone are illustrated. Parent PAHs Containing three to seven rings were found in most samples examined, some alkyl- and alkoxy-PAHs were also detected. A simple, one-step procedure for isolation of PAHs by preparative thin-layer chromatography is also reported.
cessitate combined use of several powerful separation and detection techniques. As part of a study initiated in 1977 on the characterization of mutagenic organic compounds in airborne particulates, we have attempted a comprehensive characterization of airborne PAHs by a combination of existing techniques such as capillary GC, GC-MS, LC, and a relatively new technique, online millisecond-scan LC-ultraviolet (UV) spectrometry. In this paper we report qualitative identifications of PAHs, frequency of their occurrence a t several sites in New York State, and a simple procedure for isolating the PAHs from interfering substances in the crude particulate extract. We emphasize the importance of LC/UV spectrometry as a means of achieving isomer-specific identification of PAHs.
EXPERIMENTAL SECTION Polynuclear aromatic hydrocarbons (PAH) are nearly ubiquitous in the environment because they originate from various combustion effluents, tobacco smoke, petroleum distillates, emissions from energy generation processes, and automobile exhausts. Many PAHs are either known or suspected carcinogens and mutagens (I). The carcinogenicity of a PAH is dependent on its structure, which determines the reactivity of the ultimate carcinogenic metabolites. While benzo[a]pyrene (B[a]P) is a potent carcinogen, the isomeric benzo[e]pyrene (B[e]P) is only a weak carcinogen. Consequently it is important to identify unambiguously the individual PAHs in each environmental sample. The analytical techniques (2-8) currently employed to identify airborne PAHs are gas chromatography, gas chromatography-mass spectrometry (GC-MS), and, to a lesser extent, liquid chromatography (LC), GC-MS being the most common. The analysis step is usually preceded by extraction from the sample matrix and separation of the crude sample into subgroups based on polarity and functionality. Many procedures of varying complexity have been described for isolation of PAHs from interfering substances in crude environmental samples (5, 6, 9). Some are too complex, resulting in loss of material, others are limited in scope. Gas chromatography using conventional packed columns cannot separate many important isomeric pairs, such as B[a]P and B[e]P. Recently certain nematic liquid crystals have been used successfully to separate many three to five ring compounds ( 1 0 , I l ) . However, these stationary phases are not satisfactory for analysis of samples containing PAHs of a wide range of molecular weights. Capillary GC seems to offer the best choice in this regard. Analysis of trace PAHs in environmental samples is an enormously difficult task and even when a large sample is available, a complete analytical resolution of PAHs exceeds the capability of any single analytical technique (12). Because a large number of PAHs, including many isomeric ones, are frequently present in air particulate extracts, definitive identification of individual PAHs in such samples may nePresent address: Vick IXvisions Research and Development, Richardson Vicks Inc., 1Bradford Road, Mount Vernon, NY 10553. 0003-2700/81/0353-1351$01.25/0
Materials. Glass-distilled, UV-grade solvents for LC were purchased from Burdick and Jackson Laboratories, Inc. (Muskegon, MI), Nanograde quality solvents for other purposes from Mallinckrodt, Inc. (St. Louis, MO), and glass-fiber filters from Mine Safety Appliance Co. (Pittsburgh, PA). Silica gel thin-layer chromatography (TLC) plates (G1500) were purchased from Schleicher and Schuell, Inc. (Keene, NH), and were used without further activation. PAH reference compounds were obtained from Aldrich Chemical (Milwaukee, WI), Eastman Organic (Rochester, NY), and K&K Laboratories (Plainview, NY). Commercial standards were checked for purity and, if necessary, were purified further by column chromatography on silica gel and recrystallization from an appropriate solvent. Standard solutions were prepared by dissolving the weighed amounts in a small volume of chloroform or tetrahydrofuran and diluting to the required volume with methanol. The solutions were protected from light and stored in the cold (4 OC). Apparatus. A Hewlett-Packard 5840A gas chromatograph equipped with a capillary inlet system and flame ionization detector was used. The glass capillary column (40 m X 0.35 mm) was drawn from Pyrex glass tubing on a Shimadzu GDM-1 capillary-drawing machine (Shimadzu Scientific Instruments, Inc., Columbia, MD). After three washes with methanol, concentrated hydrochloric acid, and methanol, the column was silanized with a 5% solution of 1,1,3,3,3-hexamethyldisilazanein toluene, washed again with toluene and methanol, and allowed to dry. It was coated dynamically by passing 2 mL of 0.5% SE30 solution in chloroform through it under a constant pressure of nitrogen (3-4 psi). The column showed virtually no adsorptivity for PAHs. A Finnigan Model 4000 GC-MS system equipped with an INCOS 2300 data system was used for mass spectrometry. The instrument was operated at 70 eV and scanned from 50 t o 400 amu every 2 s. LC was performed on a Waten Associates (Milford, MA) liquid chromatograph comprising two Model 6000A solvent delivery systems, a Model 660 solvent programmer, and a Model 440 dual absorbance detector. A Hewlett-Packard 3385A data system was used for recording the chromatogram and for integration of peaks. Sample Collection and Preparation. At representative sites throughout New York state, air particulate samples were collected on glass fiber fdters using standard high-volume samplers (General Metal Works, Cleveland OH), operated at an average flow rate of 1.70 m3/min for 24 h. The filters containing the particulates were Soxhlet-extracted with benzene (100 mL) for 6 h, concentrated to ca. 10 mL, and refiltered through a medium-porosity 0 1981 American Chemical Society
1352 * ANALYTICAL CHEMISTRY, VOL. 53. NO 9. AUGUST 1981
fritted filter. The solvent was completely evaporated at 60 OC in a gravity convection oven, and the residue was cooled in a desiccator under vacuum and carefully weighed. Several filter extracts from the same site were combined to give a sample of workable size. Two composite samples were fractionated into acidic, basic, and neutral fractions by liquid-liquid partitioning. The sample was first partitioned between chloroform and aqueous H&O, (10%) and aqueous KOH (10%) to extract the bases and acids, respectively, in the aqueous phases. The basic and acidic compounds were subsequently back-extracted into chloroform after a pH adjustment of the aqueous phases. The organic layer, which was left after extraction of acids and bases, was washed with water and dried over anhydrous sodium sulfate, and the solvent was evaporated to obtain the neutral fraction. TLC Isolation of PAHs. A dichloromethane solution of the neutral fraction (15-17 mg),which contains the PAHs, was applied as a thin continuous streak 1 cm from the bottom of the TLC plate. After air-drying of the solvent, the plate was placed in a developing tank containing 160 mL of cyclohexanebenzene (1:l) mixture. The plate was developed to 1cm from the top, air-dried, and observed immediately under UV light. The region containing the PAHs as determined hy R,values of naphthalene and coronene was marked, and adsorbent from this region was carefully scraped out and placed in a small glass column (9.5 X 0.6 cm). The adsorbed compounds were eluted with ether, which was subsequently evaporated to obtain the PAH fraction. A similar procedure was followed when the whole benzene extract was used instead of the neutral fraction. Recovery of several representative PAHs by the TLC procedure was greater than 85%. GC and GC-MS. For GC analysis the PAH sample was dissolved in a small volume of CHCI, (0.1-0.5 mL) and 1-2 pL aliquota were injected with stream splitting (30% split). The injector temperature was held at 230" C, and the oven temperature was programmed from 190 O C (2 min) to 290 OC at 5 OC/min. This temperature program produced optimum resolution and the minimum analysis time; the fluorene peak was clearly observable outside and solvent front. Nitrogen was used as both carrier and makeup gas. For mass spectral analysis, an SF-96 glass capillary column (30 m X 0.3 mm i.d.) was connected to the mass spectrometer via a jet separator; helium was used as the carrier gas. LC and LC-UV Spectrometry. LC in reversed-phase mode was performed with a Zorbax ODS (C18)column (4.6 mm X 25 em, DuPont Instruments, Wilmington, DE). The mobile phases were filtered and degassed before use. A solvent gradient was essential for best separation. With a flow rate of 1.6 mL/min and and B)methanol, twosolvent systems, (A) methanol-water ("0) optimum resolution and minimum analysis time were achieved by starting elution with 80% B (84% MeOH-H,O) and continuing for 20 min. A gradient to 100% MeOH over 20 min was then initiated. For certain samples the gradient was spread over 25 min for better separation of poorly resolved compounds. The W spectra of the LC eluates were obtained hy interfacing a millisecond-scan UV spectrophotometer to the LC instrument. The spectrometer (Figure 1) comprised a hydrogen continuum hollow cathode lamp, 10-pL flow-through LC cell (path length = 1 cm), and a detection system using a UV-enhanced silicon target vidicon (STV) tube mounted in the exit slit of a 0.25-m grating monochromator (295 grooves/mm) (Jerrel-Ash,Waltharn, MA) and coupled to a Model 1205 optical multichannel analyzer (OMA) (Princeton Applied Research, Princeton, NJ). The grating used can provide a theoretical spectral range of 168 nm. The flow cell was connected in series with the flow cell of the Waters d e i e b r thus allowing the spectra to be assigned to different LC peaks. The 500 channel detector target was scanned every 32 ms; 125 scans were accumulated to obtain a well-defined spectrum. To obtain the W spectrum of an LC eluate, the solvent spectrum (Io) is recorded and stored electronically in the first memory unit (A). When the solute elutes, it4 spectrum (I) is recorded and stored in the second memory unit (B).A push-button operation enabled us to determine the difference (A - B), and the eluate spectrum (Io - I) was observed on the oscilloscope. A cursor control allows accurate determination of wavelength of any peak. The analog output displayed on the oscilloscope was recorded on a chart recorder; the read out rate was 50 s for the 500-channel spectrum. The latter can be as fast as 16.4 s. For compounds eluting iso-
Flgure 1. Millisecond-scan utraviolet spectrometer interfaced to liquid chromatograph: (1) oscilloscope. (2) munichannel analyzer. (3)Micon tube. (4) monochromator, ( 5 ) flow cell, (6) quartz lens, (7)hydrogen
hollow cathode lamp, (8) LC eluate. cratically the solvent background (Io) taken at the beginning of the chromotgraphic run is used. For compounds eluting during the gradient part to the run lo was recorded at convenient points (where no constituent apparently eluted) before the component of interest starts eluting. Sometimes this resulted in minor distortion of spectral base line of components eluting under gradient conditions. R E S U L T S AND DISCUSSION To identify PAHs conclusively, first it is essential to separate them from the numerous interfering compounds that are always present in a complex mixture like airborne particulate extract. Although a cleanup method containing many steps can generate cleaner samples for final analysis, extra steps result in unavoidable loss of material and long sample-processing time. Our initial fractionation by liquid-liquid partitioning was a simple procedure by which neutral, acidic, and basic fractions were separated from the crude extract. In a typical sample, neutral compounds made up 94% (by weight) of the total benzene extractable; acidic and basic compounds constituted 4 and 2%, respectively. In early stages of the present work we found that the PAHs could be isolated by preparative TLC of the neutral fraction. Subsequently we observed that acid-base fractionation w a ~ not essential for isolation of PAH fraction; the whole extract could be applied directly for TLC fractionation. The PAH fractions isolated by both methods gave identical GC profiles. The one-step cleanup procedure was therefore used for all but two samples reported in this study. We emphasize this method which is simple and particularly convenient for analyzing small samples of air particulates-an important advantage in view of the difficulty of collecting large samples. No interfering compound was detected in any PAH fraction by GC-MS. Dong e t al. (8)has used TLC with a different ratio of solvents as used by us to separate PAH fraction from airborne particulate extract. Katz (13)used a two-stage TLC method in which the PAHs are first partially separated on aluminum oxide and then on acetylated cellulose and finally isolated and identified by fluorescence monitoring. More recently Daisy and Leyko (14) used TLC on acetylated cellulose to isolate three PAH suhfractions for subsequent GC analysis. Our procedure has the potential to separate the PAH fraction from aliphatics and other polar compounds, including the strongly basic uitrogen heterocycles, amines, and acidic and phenolic compounds. In addition to the aliphatia and PAHs, we have isolated two fractions exhibiting mutagenic properties (15) and their characterization is presently in progress. The SE-30 capillary column was evaluated with difficultto-separate PAH groups, such as, B[a]P and B[e]P. GC profiles of the PAH fractions of two air particulate extracts
1353
ANALYTICAL CHEMISTRY, VOL. 53, NO. 9, AUGUST 1981
Table I. GC Peak Identities in Figure 3 1
2 3
4 5-7
fluorene methomyfluorene methoxyfluorene phenanthrene
25 26 27 28
dimethoxyanthracene/phenanthrene
29 30
cyclopenta [d e f ]phenanthrene dime thoxyanthracene/phenanthrene 2-phenylnaphthalene fluoranthene pyrene methylphenylnaphthalene
8 9, 1 0 11 12
13 14,15 16
21 22 23
24
,
,
1
5
,
methylbenzofluoranthene/benzopyrene
quaterphenyl methylbenzofluoranthene/benzopyrene
indeno[ 1,2,3-cd]pyrene dibenz [ a, h] anthracene benzo [ghilperylene 1,2,3,4-dibenzopyrene coronene
W V
I
z
n U
i r21 I
I
benzo[e]pyrene benzo[a]pyrene
37 38,39 40 41 42 43 44
20
15
IO
methylphenylphenanthrene/anthracene
36
benzo[n]fluorene benzo[ blfluorene methyllpyreneifluoranthene dimeth ylphenylfluorene, trimethylchrysene/benz [alanthracene terphenyl, dimethylpyrene/fluoranthene benzo [g hilfluoranthene tripherqrlene chrysene
20
compound benz[a]anthracene phenylfluorene naphthanthrene, methylbenzo[ghi]fluoranthene methylchrysene/benz[a] anthracene/triphenylene phenylphenanthrenelanthracene, binaphthyl benzo[ blfluoranthene benzo ljlfluoranthene benzo [klfluoranthene
31 32 33 34 35
methyXpyrene/fluoranthene
17 18 19
I ’
no.
compound
no.
18 42
1
5
1 IO
1
-
15
,
20
,
1
25
28
I
i
MINUTES
Flgure 2. Gas Chromatogram of PAH fractions of air particulate extracts from (A) Niagara area and (B) Mount Vernon.
are shown in Figure 2. Retention times of chromatographic peaks were compared with those of representative parent PAHs and compounds cmtaining from three to seven rings were identified (Table I). Coronene (seven rings) eluted in less than 30 min (Figure 3), in contrast to the more than 80 rnin elution time reported elsewhere (16). Phenanthrene and anthracene were easily separated by the capillary column used. Chrysene, benz[a]anthracene (B[a]A), and triphenylene (peaks 23-25) could not be resolved completely on the present column although the first two had a retention time difference of 0.1 min. Three isomeric bennofluoranthenes (peaks 30-32) were not completely resolved by the capillary column used in this work; several variations of chromatographic conditions did not improve the separation of these isomers (17). Other investigators have reported difficulties in separating these two groups of compounds (16). B[a]P and B[e]P were base-line resolved by this column. The occurrence of two separate peaks was dependent on the relative concentrations of the two compounds present in a ciample. In most samples because B[e]P was present in much higher concentration than B[a]P, one peak with a distinct shoulder was observed. The major constituents observed in the chromatogram in Figure 3 were present in all of the air particulate PAH fractions we examined. The GC-separated components were further characterized by GC-MS with a glass capillary column. Because of the
50
IO0
I50
200
250
300
M/E
Flgure 3. Mass spectra of (A) peak 3, methoxyfluorene, and (B) peak 6, dimethoxyanthracene/phenanthrene(from Figure 2A).
instrumental limitations, chromatographic conditions for the GC-MS work were optimized separately for best resolution. PAHs exhibit strong molecular ions on electron impact, which permits reliable measurement of molecular weight and hence identification of a particular PAHs ring system. m l e values of parent ions of all peaks observed in the reconstructed ion chromatogram were determined. Mass chromatograms of the parent ions and their significant fragment ions (very few for PAHs) were generated, and computer-assisted background substraction was used to obtain clean spectra. These spectra were compared with those of reference compounds when available, otherwise they were compared with the computer-stored library spectra. By GC-MS most components were confirmed to be parent PAHs; however, some alkyl-PAHs were detected in most samples. Several methoxy-PAHs were detected in all samples examined: although no reference standards were available, the mass spectral fragmentation pattern was characteristic of the structures assigned. For example, the parent ion in the mass spectrum of (Figure 3A) peak 3, identified as methoxyfluorene, gave strong fragment ions corresponding to the loss of a CH3group and CHzO group. Mass spectrum of peak 6, identified as dimethoxyanthracene/phenanthrene,showed
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ANALYTICAL CHEMISTRY, VOL 53, NO. 9, AUGUST 1981
BenzoI)!fiuoronlhene
a
\.
MINUTES Figure 4. Liquid chromatogram of (A) benzo [ a ]pyrene and benzo-
[ elpyrene, (B) benzo[b]fluoranthene, benzo[j]fluoranthene, and benzo[k]fluoranthene,and (C) triphenylene and chrysene.
Table 11. LC Peak Identities in Figure 6 compound no. compound no. 1 phenanthrene 2 fluoranthene 3 pyrene
4
9 10 11 triphenylene 12 chrysene 13 benz[a]anthracene 14 benzolilfluoranthene 15
5 6 7 8 benzorelevrene
I
benzo [ blfluoranthene benzo [ k Ifluoranthene
benzo [alpyrene dibenz[ a, hlanthracene benzo [ghilperylene indeno[ 1,2,3-cd]pyrene coronene
fragments characteristic of this structure (Figure 3B). All compounds characterized by GC-MS are listed in Table I. Although GC-MS is the single most powerful technique commonly applied to identify constituents of a complex mixture, electron impact (EI) mass spectra of PAHs lack significant fragmentation. Consequently the spectra cannot differentiate between structural isomers of PAHs such as chrysene and B[a]A-a limitation particularly when chromatographic separation is lacking. Additional independent evidence for isomer-specific identification is important particularly since carcinogenicity of PAHs is isomer dependent. Several authors have reported satisfactory results from application of LC to analysis of PAHs (7,8). The Zorbax ODS column used in this study performed excellently with a methanol-water mobile phase gradient. LC retention times were criteria for preliminary identification. By our method triphenylene was well separated from chrysene or B[a]A (Figure 4), although the latter two were only partially resolved when present together. Elevated column temperature of up to 35O C did not improve this separation. Similar difficulty has been experienced by other authors (8,18). B[a]P and B[e]P were well separated by LC (Figure 41, as were benzolilfluoranthene (BVIF), benzo[blfluoranthene (B[b]F), and benzo[k] fluoranthene (B[k]F). B[k]F was clearly separated from B[e]P or B[a]P, although some authors have reported failure in these separations (18). We did not obtain adequate separation between B[e]P and B[b]F in a multicomponent mixture; this pair always appeared as an unresolved peak. LC profiles of two PAH fractions, typical of all samples examined, are shown in Figure 5. Peak identities are listed in Table 11. Chromatographic conditions were optimized for best separation and minimum analysis time. In our work coronene eluted in 42 min, some authors have reported elution times of greater than 100 min for this compound (8). Variation of flow rate or mobile-phase composition did not noticeably improve resolution. Other analytical approaches are possible. For example, Das and Thomas (18) have used a Zorbax ODS column with acetonitrile-water as a mobile phase. They attempted the separation of nine PAHs, using the more selective fluorescence detection system. With the appropriate excitation and emission wavelengths one component of a coeluting pair was detected in preference to the other. Thus B[a]A was moni-
MINUTES
Flgure 5. Liquid chromatogram of PAH fractions of air particulate extracts from (A) City College of New York and (B) Mount Vernon.
tored in the presence of chrysene, although the two were not chromatographically separated. However, a number of chromatographic runs would still be needed to detect a wide range of PAHs. In another recent study, Ogan et al. (19) separated 16 synthetic PAHs using a Perkin-Elmer HC-ODS reversed-phase column with acetonitrile-water as a mobile phase and a programmable fluorescence detection system. Separation of chrysene and B[a]A was reported but not of BP]F from B[b]F or B[k]F. The late-eluting peaks were slightly broader compared to similar peaks in our work presumably because Zorbax ODS packing has 6-pm particles as compared to the 10-pm particles present in the HC-ODS column packing. The same authors have also compared the ability of a number of commercial ODS columns to separate isomeric PAHs (20). Recently Wilkinson et al. reported similar results for analysis of PAHs in aqueous effluents (21). We are presently evaluating the separation capability of the HC-ODS column for complex PAH mixtures. Except for a few difficult-to-separate pairs, our present method can separate a wide range of PAHs normally encountered in environmental samples using a commonly used UV detector. The column can handle relatively large size samples without losing any resolution and reproducibility-an advantage in analyzing very complex mixtures. Retention time data as generated from use of a single wavelength detector does not, however, provide adequate confirmation for identity of PAHs particularly when the sample has a complex compositon. Since PAHs possess strong and distinctive absorbance in the UV region and since the spectra of isomers are significantly different, UV spectra of LC eluates generated in real time can be invaluable for fingerprinting of the eluates. We have utilized a millisecond scan UV spectrometer enabling determination of spectra of LC eluates in a continuous flow mode, a distinct advantage over many commercial scanning UV detectors which require stopping of column flow or collecting fractions and determining W spectra. Some investigators have used vidicon and diode array spectrometer to determine absorbance and fluorescence spectra of LC eluates (22-24). A recent review describes possible applications of various optoelectronic image
ANALYTICAL CHEMISTRY, VOL. 53, NO. 9, AUGUST 1981
detectors (25). A few rapid-scan spectrometers have recently become commercially available (26). In the present study, the spectral window of the instrument which is adjustable was calibrated for 204-348.7 nm using the atomic spectral lines of Zn and Hg. One nanogram or lower amount of most PAHs produced distinctive UV spectra. To confirm the identity of the constituents, we compared the UV spectrum of the eluate with that of the suspected reference compound. A superimposable spectrum was the criterion for identification of a single component peak. For coeluting compounds presence of essential spectral features was considered adequate. For example, the retention time of peak 5 (Figure 5B) corresponded to that of both chrysene and B[a]A, but the UV spectra of this isomeric pair are distinctly different (Figure 6). Scanning of the central part of peak 5 gave a spectrum (Figure 6) superimposable on the UV spectrum of chrysene. Scanning of the trailing edge (peak 6) gave a spectrum (Figure 6) which contained the essential features of the spectra of both chrysene and B[a]A. Thus the presence of both compounds in this sample was unequivocally established despite lack of chromatographic separation. The spectrum of the leading edge of the peak was not readily identifiable. As mentioned earlier, B[e]P, B[b]F, and perylene were not sufficiently resolved by the LC method used. The retention time of peak 9 suggested that this peak may represent any or all three of these compounds. A scan of the leading edge of the peak (no. 8) gave a spectrum (Figure 6) superimposable on that of B[e]P. Another scan of the center of the peak (no. 9) produced a spectrum (Figure 6) superimposable on that of B[b]F. Scans a t several other parts of the peak failed to establish the presence of perylene. The unidentified peak (U) in Figure 5B had a retention time which corresponds accurately to that of anthracene, but its UV spectrum was clearly different than that of anthracene. UV spectra of all peaks having retention times corresponding to available authentic standards were determined and compared with spectra of reference standards. The three benzofluoranthenes-B[b]F, B[I']F, and B[k]F-not completely resolved by GC were separated by LC, and their UV maxima were sufficiently different to enable their definite identification. UV spectra of compounds eluting under gradient conditions did not show any significant base line distortion. T h e high resolving power of LC coupled with the fingerprinting power of UV spectrometry enabled isomer-specific identification of PAHs. Determination of peak purity is also important for quantitation purpose. Confirmed identification by this novel technique can be achieved preferably when an authentic standard of the compound in question is available. Comparison of the spectrum of an unknown sample component'with a literature spectrum may sometimes be inconclusive. However, computer interfacing of the vidicon spectrometer could allow generation of spectral library and search programs can be developed to compare LC eluate spectra with library spectra. Computer interfacing will also permit continuous spectral acquisition during a chromatographic run, displaying a chromatogram at optimal wavelength for various components, enhanced detectability by integrating spectral output for the whole range, and subtraction of more accurate solvent background by storing spectra for blank gradient run prior to running the sample. The LC-UV method was applied to 14 air particulate samples collected from several parts of New York state and the UV spectral data in conjunction with LC retention time, GC retention time, and GC-MS data enabled unambiguous characterization of 15 PAHs (Table 111) in most samples. The majority of these PAHs are proven carcinogens and mutagens. Many other PAHs were characterized with less certainty by
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1356
ANALYTICAL CHEMISTRY, VOL. 53,
NO. 9,
AUGUST 1981
LITERATURE CITED
I
Y
I
P
7
2870
m'
204 -
WAVELENGTH (nm)
Figure 6. Ultraviolet spectra LC eluates (from chromatogram in Figure
5f3) and some PAH standards.
GC-MS. It is noteworthy that the 15 compounds listed in Table 111 were present in ambient air even at the top of Whiteface Mountain (elevation ca. 5000 ft), although their concentrations were presumably lower than in samples from industrial areas.
ACKNOWLEDGMENT We thank R. Parillo and E. LeGere for technical assistance and P. Dymerski for assistance in mass spectral work.
(1) Freudenthal, R., Jones, P. W., Eds. "Polynuclear Aromatic tiydrccarbons: Chemistry, Metabolism and Carcinogenesis"; Raven Press: New Yo&, 1976. (2) Lao, R. C.; Thomas, R. S.;ON,H.; Dubois, L. Anal. Chem. 1973, 45, 906. (3) Karasek, F. W.; Denney, D. W.; Chan, K. W.; Clement, R. E. Anal. Chem. 1978, 50, 62. (4) Lao, R. C.; Thomas, R. S.;Monkman, J. L. J. Chromatogr. 1975, 172, 681. (5) Lee, M. L.; Novotny, M.; Bartle, K. D. Anal. Chem. 1978, 48, 1566. (6) Cautreels, W.; Van Cauwenberghe, K. Atmos. Envlron. 1978, 10, 447. (7) Fox, M. A.; Stanley, S. W. Anal. Chem. 1978, 48, 992. (8) Dong, M.; Locke, D. C.; Ferrand, E. Anal. Chem. 1978, 48, 368. (9) Novotny, M.; Lee, M. L.; Bartie, K. D. J. Chromatogr. Sci. 1974, 12, 607. (10) Janini, G. M.; Muschik, G. M.; Zielinski, W. L., Jr. Anal. Chem. 1978, 48, 1879. (11) Janini, G. M.; Muschik, G. M.; Zielinski, W. L., Jr. Anal. Chem. 1978, 48, 809. (12) Blumer, M.; Giger, W. Anal. Chem. 1974, 46, 1633. (13) Katz, M.; Sakuma, T.; Ho, A. Environ. Scl, rechnol. 1978, 12, 909. (14) Daisy, J. M.; Leyko, M. A. And. Chem. 1979, 57, 24. (15) Choudhury, 0. R.; Bush, 8.; Miller, T.; Woiin, M. J., unpublished work. (16) Giger, W.; Schaffner, C. Anal. Chem. 1978, 50, 243. (17) We have recently developed ca lllary columns that can base-llne-resolve chrysene, B[a]A and B[bfF, B[k]F. However, in the presence of triphenylene and B[/]F, respectively, only partial separation of the components in the two groups can be achieved. (18) Das, B. S.;Thomas, G. H. Anal. Chem. 1978, 50, 967. (19) Ogan, K.; Katz, E.; Slavin, W. Anal. Chem. 1979, 51, 1315. (20) w a n , K.; Katz, E. J. chromarogr. 1980, 188, 115. (21) Wllkinson, J. E.; Strup, P. E.; Jones, P. W. I n "Polynuclear Aromatic Hydrocarbons"; Jones, P. W., Leber, P., Eds.; Ann Arbor Science Publishers: Ann Arbor, MI, 1979; p 217. (22) McDoweil, W. E.; Pardue, H. L. Anal. Chem. 1977, 49, 1171. (23) Jadarnec, J. R.; Saner, W. A. Anal. Chem. 1977, 49, 1977. (24) Milano, M. J.; Lam, S.;Savonis, M.; Pautler, 0. B.; Pav, J. W.; Grushka, E. J. Chromatogr. 1978, 149, 599. (25) Talrni, Y. ACS Symp. Ser. 1979, No. 102, 1. (26) James, G. E. Paper presented at the Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, paper no. 164, March 1981.
RECEIVED for review October 8,1980. Resubmitted February 18, 1981. Accepted May 6, 1981. This work was partially supported by New York State Health Research Council Grant HR414. Part of this work was presented at the 176th National Meeting of the American Chemical Society, Miami Beach, FL, Sept 1978.
