Environ. Sci. Technol. 1900, 22, 1440-1447
(3) Elzerman, A. W.; Coates, J. T. In Sources and Fates of Aquatic Pollutants; Hites, R. A., Eisenreich, S. J., Eds.; Advances in Chemistry 216;American Chemical Society: Washington, DC, 1987;Chapter 10. (4) Wu, S.-C.; Gschwend, P. M. Environ. Sci. Technol. 1986, 20,717-725. ( 5 ) Crank, J. The Mathematics of Diffusion,2nd ed.; Clarendon: Oxford, England, 1975. (6) Thibodeaux,L. J. Chemodynamics; Wdey: New York, 1979. (7) Karickhoff,S. W.; Morris, K. R. Environ. Sci. Technol. 1985, 19,51-56. (8) Brown, D. A.; Fulton, B. E.; Phillips, R. E. Soil Sci. SOC. Am. Proc. 1965,28,628-632. (9) Karickhoff, S.W.; Brown, D. S.; Scott, T. A. Water Res. 1979,13,241-248. (10) Pavlou, S. P.; Dexter, P. N. Environ. Sci. Technol. 1979, 13,65-71. (11) Means, J. C.; Wood, S. G.; Hassett, J. J.; Banwart, W. L. Environ. Sci. Technol. 1980,14,1524-1528. (12) Curl, R. L.;Keolelan, G. A. Environ. Sci. Technol. 1984, 18,916-922. (13) Voice, T. C.; Weber, W. J., Jr. Water Res. 1983, 17, 1433-1441. (14) Karickhoff, S.W.J. Hydraul. Diu., Am. SOC.Civ. Eng. 1984, 110,707-735. (15) Schellenberg, K.; Leuenberger, C.; Schwarzenbach, R. P. Environ. Sci. Technol. 1984,18,652-657. (16) Urano, K.; Murata, C. Chemosphere 1986, 14,293-299. (17) DiToro, D. M. Chemosphere 1985,14,1503-1538. (18) Gshwend, P. M.; Wu, S A . Enuiron. Sci. Technol. 1985, 19,90-96.
(19) Baker, J. E.; Capel, P. D.; Eisenreich, S. J. Environ. Sci. Technol. 1986,20,1136-1143. (20) Paris, D. F.; Steen, W. C.; Baughman, G. L. Chemosphere 1978,7,319-325. (21) Curtis, G. P.; Reinhard, M.; Roberts, P. V. In Geochemical Processes at Mineral Surfaces; Hayes, K. F., Davis, J. A., Eds.; ACS Symposium Series 323; American Chemical Society: Washington, DC, 1986;pp 191-216. (22) Voice, T. C.; Weber, W. J., Jr. Environ. Sci. Technol. 1985, 19,789-796. (23) O'Connor, D. J.; Connolly, J. P. Water Res. 1980, 14, 1516-1523. (24) Mackay, D.; Powers, B. Chemosphere 1987,16,745-757. (25) Voice, T. C.; Rice, C. P.; Weber, W. J., Jr. Environ. Sci. Technol. 1983,17,513-518. (26) Shiu, W. Y.; Mackay, D. J . Phys. Chem. Ref. Data 1986, 15,911-929. (27) Rapaport, R. A.; Eisenreich,S. J. Environ. Sci. Technol. 1984,18,163-170. (28) Thibodeaux, L. J.; Reible, D. D.; Fang, C. S. In Pollutants in a Multimedia Environment; Cohen, Y . , Ed.; Plenum: New York, 1986;pp 49-64. (29) Valsaraj, K. T.;Wilson, D. J. Colloids Surf. 1983,8,203-221. Received for review March 7,1988.Accepted June 3,1988. Funds for this project were provided by the Department of Chemical Engineering, University of Arkansas, and ArkansaslTexas Eastman Kodak Corp. This paper (No. 01F23)was presented at the American Chemical Society International Chemical Congress of the Pacific Basin Societies, Honolulu, Hawaii, December 16-21,1984.
Characterization of Polar Polycyclic Aromatic Compounds in a Heavy-Duty Diesel Exhaust Particulate by Capillary Column Gas Chromatography and High-Resolution Mass Spectrometry Jose M. Bayona,+Karin E. Markides, and Milton L. Lee* Department of Chemlstry, Brlgham Young University, Provo, Utah 84602
rn Polar normal-phase HPLC fractions of a heavy-duty diesel exhaust particulate, a National Bureau of Standards (NBS) standard reference material (SRM) 1650, were analyzed by capillary column GC coupled to both low- and high-resolution mass spectrometry (HRMS) using electron impact (EI) and negative ion chemical ionization (NICI). Over 80 polycyclic aromatic compounds (PAC), belonging to many different chemical classes (anhydrides, carboxaldehydes, diazaarenes, cyclic imides, nitrohydroxy-PAC, nitroaza-PAC, nitrodiaza-PAC, nitrolactones, and quinones) were tentatively identified. Ten of them were positively identified by comparison of retention times with authentic standards. Among them, phenazine and phthalic anhydride were postively identified for the first time in diesel exhaust particulates. In addition, cyclic imides and their alkylated derivatives were tentatively identified for the first time. Other novel polar chemical classes of PAC were evidenced by NICI MS using a direct-insertion probe. Introduction
Organic compounds adsorbed onto the particulate phase of diesel exhaust possess direct-acting mutagenicity (produce a positive response in the Ames assay without the f Current address: CID-CSIC, Environmental Chemistry Department, Jordi Girona Salgado, 18-26, 08034 Barcelona, Spain.
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addition of microsomal S-9 enzymes) in short-term bioassays ( I , 21, and most of these particulates are in the respiratory size range (3). Approximately 40% of the direct-acting mutagenicity of diesel particulates can be accounted for by several nitrated polycyclic aromatic compounds (N02-PAC)(4), but the remaining mutagenicity is distributed among other polar chemical classes, specific compounds of which remain unknown. An increase in the utilization of diesel-powered vehicles during this decade has become a cause of concern, and much effort has been devoted to the identification of compounds responsible for this mutagenicity. Methods for sampling and fractionation of the soluble organic fraction of diesel exhaust particulates are well established, and normal-phase HPLC for fractionation has been popular because of its high speed and reproducibility (5,6). However, various combinations of chromatographic and spectroscopic techniques are required to analyze these fractions because of their complexities. Polycyclic aromatic hydrocarbons (PAH) in diesel exhaust particulate matter have been characterized already (7, 8)) but they do not contribute to the direct-acting mutagenicity (9). NO,-PAC have been detected in the intermediate polarity fractions, and much effort has been devoted to their characterization because they exhibit direct-acting mutagenicity (10). High-resolution gas chromatography coupled to nitrogenselective thermionic detection (NPD)(11))electron capture
0013-936X/88/0922-1440$01.50/0
0 1988 American Chemical Soclety
detection (ECD) (12, 13), chemiluminescence detection (CD) (14),and negative ion chemical ionization mass spectrometry (NICI MS) (12, 15, 16) have been used. However, only a few reports have been published on the most polar fractions of diesel exhaust particulates (17,181. Low vapor pressures and thermal labilities of these components make difficult their analysis by GC-MS therefore, a combination of analytical techniques is required. In this study, the polar HPLC fractions of a National Bureau of Standards (NBS) standard reference diesel exhaust particulate (NBS 1650) were characterized with the aim of providing information for use in correlating the mutagenicities of these fractions with their compositions. GC, using excellent deactivated fused silica capillary columns with on-column injection, was coupled to both low- and high-resolution MS. NICI MS using methane as a reagent gas was used because of its selectivity for PAC substituted with electron-withdrawing functional groups. Therefore, it could enable the characterization of minor components. Direct introduction probe (DIP) NICI and low-energy electron impact (EI) HRMS was used to characterize components that give too low recoveries under the GC-MS conditions. Experimental Section Sample Origin. Normal-phase HPLC fractions of NBS SRM 1650 were provided by T.E. Jensen and D. Schuetzle (Ford Motor Co., Dearborn, MI). The SRM was collected from the heat exchangers of a dilution tube facility following 200 engine hours of particulate accumulation. Different engines operating under a variety of conditions were used to generate the particulate material (18). A 3.9-g quantity of NBS SRM 1650 was extracted with dichloromethane for 24 h and then with methanol for 24 h in a Soxhlet apparatus under dry nitrogen. The aliphatic fraction was removed by silicic acid adsorption chromatography (170 mm X 12 mm id.) with hexane. A methanol fraction was then collected and further fractionated by normal-phase LC with a 300 mm X 7.8 mm i.d. semipreparative column (10-pm p-Porasil; Waters Associates, Milford, MA) (11)to give fractions of increasing polarity and designated as fractions 7-9. Standards. Phthalic and 1,g-naphthalic anhydrides and 9-xanthenone were purchased from Aldrich (Milwaukee, WI). 5-Nitroisoquinoline, l-hydroxy-2-nitronaphthalene, 5-nitroindole, 9-hydroxy-2-nitrofluorene, dihydroxynitropyrene, 5-nitroindoline, 5-nitroquinoline, 8-nitroquinoline, 3-nitrodibenzofuran, 2-nitro-9-hydroxyfluorene, and 2-nitrodibenzothiophene were provided by T. E. Jensen. Other standard compounds were available in our laboratory. Fused Silica Capillary Column Preparation. Fused silica tubing (200 pm i.d.) was purchased from Polymicro Technologies, Inc. (Phoenix, AZ). Columns were rinsed with 5 mL of HPLC-grade water and were dried at room temperature under nitrogen purge overnight. After being dried, they were deactivated by using methylhydropolysiloxane as previously described (19). SE-33 stationary phase (Applied Science, State College, PA) was statically coated at room temperature from a solution of 5 mg mL-l in n-pentane. Columns were conditioned under nitrogen gas flow during temperature programming from 40 to 280 "C at 1 OC min-l and holding the final temperature for 60 min. Cross-linking was performed statically with azotert-butane (20). Columns were rinsed after cross-linking by using n-pentane, and they were then conditioned under nitrogen gas flow during programming from 40 to 280 "C and holding the final temperature overnight. Column inertness was evaluated by injection of acidic and basic test
compounds as previously described (19). Column efficiency was determined isothermally at 150 "C with n-alkanes (Cl1-ClS) at a hydrogen carrier gas velocity of 50 cm S-1.
Gas Chromatography. HPLC fractions 7-9 were analyzed with a Carlo Erba 4160 gas chromatograph with an FID. Samples were injected by using splitless and oncolumn injection modes at 50 and 80 "C, respectively. The oven initial temperature was held for 2 min and then programmed to 280 "C at 6 "C mi&. Hydrogen was used as a carrier gas at 80 cm s-l. Fraction 9 was either too nonvolatile or too polar to be analyzed by GC-MS and therefore was not studied further. Gas Chromatography-Mass Spectrometry. Analyses using GC with low-resolution electron impact ionization MS were performed with a Hewlett-Packard GC-MSD. The electron impact ionization energy was 70 eV, and the scan speed was 0.85 scan s-l. The ion source and analyzer temperatures were 250 and 230 "C, respectively, and the helium carrier gas was set at 50 cm s-l. Other chromatographic conditions were identical with those described in the GC analysis section. High accuracy (2000 resolution) NICI MS was performed by using a Finnigan MAT 8430 instrument coupled to a Varian 3400 GC, with methane as a chemical ionization gas at 0.15 Torr ion source pressure. The ionization energy of the reagent gas was 60 eV, the ion source temperature was 200 "C, and the scan speed was 0.6 scan s-l. Direct-Probe Mass Spectrometry. Direct-probe MS analyses were performed by using a Finnigan MAT 8430 mass spectrometer at 10000 resolution (10% valley). The electron impact ionization energy was 40 eV. Exact mass measurements were performed by averaging scans with a wide mass conversion algorithm. The probe temperature was programmed from 40 to 260 "C at 20 "C min-l. Negative ion CI mass spectra were obtained with the MS under the same conditions as described above for using the GC with NICI. Results and Discussion Analysis of complex mixtures of PAC present in the soluble organic fraction of diesel exhaust particulates requires high-resolution analytical techniques. GC using well-deactivated fused silica capillary columns should be the preferred analytical technique for such compounds if they are volatile and thermally stable. Various selective stationary phases can improve the resolution of selected isomeric PAC (21, 22), but the resolution of complex mixtures of PAC must rely mainly on efficiency. Hence, a nonselective, nonpolar stationary phase (methylpolysiloxane, SE-33) was used in the present study. Figure 1 shows chromatograms of fractions 7 and 8. Both fractions were extremely complex as indicated by the large unresolved hump in the base line. The identifications of many of the resolved compounds in both fractions, which were mainly polar PAC, are listed in Table I. In addition, fractions 7 and 8 were analyzed by direct-probe MS in order to compare with the GC-MS results. The compounds detected by this approach are listed in Table 11. As can be seen, several of the compounds were found in both fractions 7 and 8, indicating that the LC fractionation was not complete for these compounds. Under NICI conditions using methane as a reagent gas, M- was usually the base peak, and almost no fragmentation was observed. Methane acts as a moderator, and a large population of thermal electrons is produced, which can be captured by high electron affinity molecules (23). PAC containing nitro, anhydride, quinone, keto, and aldehyde functional groups were selectively detected by NICI MS Environ. Sci. Technol., Vol. 22, No. 12, 1988
1441
Table I. GC-MS Characterization of Organic Adsorbates in Diesel Particulate Matter (NBS 1650)
fraction no. (re1 abund)"
peak no. 1 2 3 4 5 6 7, 8,lO 9 11, 13 12
14 15 16
17-19 20-22 23 24, 28 25 26, 27 29 30 31 32 33 34 35 36 37,39
7 (0.14), 8 (0.16) 7 (0.10), 8 (0.14) 8 (0.10) 8 (0.05) 7,d 8 (0.12) 8 (0.14) 7,d 8 (0.15) 7 (0.22) 7 (0.15) 7 (0.05), 8 (0.18) 7d 7d 7 (0.28) 7,d 8 (0.11) 7 (0.11) 7,d 8d 7,d 8d 7,d 8d 7,d 8d 7,d 8d 7d 7 (0.12) 7 (0.20) 7 (0.40), 8 (0.71) 8 (0.12) 8 (0.08) 7 (O.ll), 8 (0.05) 7 (0.10) 7d 7d 7 (0.20), 8 (0.38) 7 (0.12) 8 (0.42) 7 (0.08) 7 (0.05) 8 (0.32) 7,d 8 (0.51) 8 (0.20) 7,d 8d 7d
38 40 41 42 43 44 45 46 47 48, 49 50,51 52-54 55,56
7 (0.16) 7 (0.15), 8 (1.00) 7 (0.16) 7 (0.14) 7 (0.10), 8 (0.16) 8 (0.18) 7 (0.17) 8 (0.25) 7 (1.00), 8 (0.13) 8 (0.10) 7 (0.50) 7 (0.31), 8d 7 (0.35), 8d 7d
57 58 59 60
7 (0.18), 8 (0.07) 7 (0.18), 8 (0.09) 7 (0.27), 8 (0.06) 7 (0.16) 7d 7d 7,d 8d 7,d 8d 7,d 8d 7,d 8d
MWb
compound(s)
115.028 129.043 122.037 143.058 148.017 115.062 162.032 133.052 147.071 186.078 158.037 158.037 156.059 176.047 163.027 218.033 175.038 175.038 174.043 174.043 174.043 161.028 170.075 163.027 179.022 181.056 163.023 177.047 188.011 189.042 180.068 170.075 177.046 184.050 196.052 237.079 198.038 198.068 191.022 153.006 194.071 180.068 214.135 196.052 194.072 212.084 250.021 194.073 198.038 226.099 206.073 2 12.045 226.063 273.079 230.075 230.075 230.075 278.152 220.048 220.048 274.073 274.073 288.090 288.090
hydroxypyrrolidine-2,5-dioneisomer C1 hydroxypyrrolidine-2,5-dioneisomers benzoic acid isomer Cz hydro~ypyrrolidine-2,5-dione phthalic anhydride unknown C1 phthalic anhydride isomers hydroxyindole isomer C1 hydroxyindole isomers unknown naphthoquinone isomer naphthoquinone isomer naphthalenecarboxaldehyde isomer Cz phthalic anhydride hydroxyphthalimide isomers dinitronaphthalene isomer nitrocinnoline isomer nitrocinnoline isomer nitroquinoline isomer nitroquinoline isomer nitroquinoline isomer Cz hydroxyindole isomers phenylphenol isomers hydroxyphthalimide isomer unknown unknown hydroxyphthalimide isomers C1 hydroxyphthalimide isomer naphthodiquinone isomer nitrohydroxynaphthalene isomer phenazine m + p-phenylphenol isomers C1 hydroxyphthalimide isomer naphthalenedicarboxaldehyde fluorenequinone or xanthene C1 NO2-phenanthrene/-anthracene isomer naphthalene anhydride isomer hydroxyxanthene or dihydroxyfluorene nitronaphthalene lactone isomer nitrobenzoquinone isomer C1 9-fluorenone benzo[c]cinnoline unknown xanthene- or fluorenequinone isomer 9-anthrone C1 hydroxyxanthene isomer dipropylphthalate C1 9-fluorenone isomer 1,8-naphthalic anhydride Cz hydroxyxanthene isomers phenanthrene-/anthracenecarboxaldehydeisomers C1 naphthalic anhydride isomers Cz naphthalic anhydride isomers nitrochrysene isomer benzo[a]fluorenone benzo[blfluorenone 7-H-benzo[de]anthracen-7-one (benzanthrone) dibutylphthalate C1 dinitroindene isomer C1 dinitroindene isomer nitroazachrysene isomer nitroazachrysene isomer C1 nitroazachrysene isomer C1 nitroazachrysene isomer
ident method' e, f e, f e, g e, f e, f, g e e, f e e e, f f f e, f e, f e, f f f f f f f e e e, f e e, f e, f e, f f f e, g e, g e, f e, f e, f e, f e, f e f f e, f e, g e, f e, f e, f e e, f e, f e, f, g e e, f e, f e, f f e, f, g e, f , g e, f, g e, f f f f
f f f
Relative abundance was normalized to the most abundant component of each fraction in the E1 TIC chromatogram. Experimental molecular weight determined at 10000 resolution. CIdentification: (e) GC-E1 MS, (f) GC-NICI MS, and (9) matching retention with standard comDound. dDetected. but not ouantified.
(Tables I and 11). However, hydroxyl-substitutedPAC and azaarenes could only be detected by E1 MS (Table I). Furthermore, some polar types of PAC were detected only by use of the DIP because of either their low volatilities or thermal labilities (Table 11). Their identifications were 1442
Environ. Sci. Technol., Vol. 22, No. 12, 1988
based on molecular weights determined by NICI MS and low voltage (40 eV) E1 MS which permitted empirical formula calculation. This analytical approach did not distinguish between isomers; thus, only tentative identifications were possible.
A
4
41
I
0
30
YlN
B
Figure 1. Gas chromatograms of NBS SRM 1650: (A) fraction 7 and (8)fraction 8. Compounds identified are listed in Table I.
Anhydrides. Anhydrides of dicarboxylic acids were identified in both fractions, but only in fraction 'I were they major components. In this fraction, 1,8-naphthalic anhydride was identified as a major component of this chemical class (Figure lA), and its C1-C3 alkyl-substituted derivatives were also present (Figure 2). Dinaphthalic anhydride was identified in the same fraction by direct-probe MS. Phthalic anhydride and its C1and C2alkyl 1-substituted derivatives were positively identified in diesel exhaust for the first time (Figure 1B). The occurrence of anhydrides in diesel exhaust and air particulates was previously reported (18, 24), but their
exact origin is unknown. Nevertheless, they could originate from alkyl diacids, which are common additives of diesel fuels (25), or by the oxidation of certain PAH during combustion at elevated temperatures, particularly those PAH with five-membered unsaturated rings (26). Their contribution to the direct-acting mutagenicity is unknown, although aliphatic cyclic anhydrides have demonstrated carcinogenic properties (27), and some aromatic anhydrides are moderate mutagens (26). Ketones and Carboxaldehydes of PAH. Both chemical classes were identified as major components of fraction 7 by GC-MS. 7H-Benz[de]anthracen-7-one(benzEnviron. Sci. Technol., Vol. 22, No. 12, 1988
1443
Table 11. Direct-Probe NICI MS Characterization of Organic Adsorbates in Diesel Particulate Matter (NBS1650)
MWa 138.043 145.053 153.006 160.020 162.043 174.043 175.038 188.011 189.042 191.022 194.999 195.068 201.064 202.027 203.022 206.033 208.052 212.058 216.042 218.033 219.068 220.0 48 224.058 226.074 231.053 233.047 238.026 239.058 241.036 245.014 247.067 248.058 255.053 261.079 262.074 265.037 273.079 274.073 275.095 278.152 284.043 287.095 289.110 292.048 297.079 299.069
re1 abundb 0.12 0.13 0.25 0.30 0.25 0.35 0.18 1.00 0.11 1.00 0.10
0.20 0.27 0.33 0.12 0.30 0.13 0.12 0.14 0.22 0.12 0.31 0.43 0.22 0.24 0.50 0.12 0.58 0.19 0.20 0.66 0.26 0.32 0.57 0.34 0.71 0.24 0.22 0.21 0.33 0.14 0.20 0.22, 0.10 0.13 0.11 0.18
fraction 8 8 8 8 8 8 8 7 7 8 7 8 8 7 8 8 7 7 7 8 8 8 8
I 7 7 7 7 7 7 7 7 7 7 7 8 7 8 7 8 7 7 7, 8 7 7 8
tentative identification
C1 nitropyridine hydroxyquinoline/-isoquinoline nitrobenzoquinone unknown nitroindole nitroquinoline/-isoquinoline nitrocinnoline naphthodiquinone nitrohydroxynaphthalene nitronaphthalene lactone hydroxynitrobenzothiophene hydroxyacridine/-phenanthridine unknown C1 naphthodiquinone nitronaphthoquinone dinitroindene anthrone nitrocarbazole Cz naphthodiquinone dinitronaphthalene hydroxyazapyrene C1 dinitroindene nitroacridinel-phenanthridine C1-substitutednitrocarbazole dihydroxynitrobiphenyl azapyrene-/azafluoranthenequinone phenanthrene-lanthracenediquinone hydroxynitrophenanthrene/-anthracene nitrophenanthrene/-anthracene lactone hydroxynitrodibenzothiophene nitrofluoranthene/-pyrene NO2-azafluoranthene/-pyrene dihydroxynitrophenanthrene/-anthracene C1 nitrofluoranthene/-pyrene pyrenediquinone nitropyrene lactone nitrochrysenel-benzanthracene nitroazachrysene Cz nitrofluoranthenel-pyrene dibutylphthalate ester hydroxydinitrophenanthrene/-anthracene C1 nitrochrysene hydroxynitrochrysene/-benzanthracene dinitropyrenel-fluoranthene nitrobenzopyrene nitrodiazabenzopyrene
a Experimental molecular weight determined at 10 000 resolution. *Relative abundance normalized to most abundant ion in the mass spectrum.
anthrone), benzo[a]fluorenone, and benzo[b]fluorenone (Figure 1A) were positively identified. Naphthalene, phenanthrene, and anthracene carboxaldehydes were tentatively identified in fraction 7 (Figure lA), whereas naphthalenedicarboxaldehydewas the only dialdehyde identified. The presence of this chemical class of PAC in diesel exhaust particulates has already been reported, (17,28,29),and they are the major components in the medium polarity fractions. Hydroxy-Substituted PAH. These compounds were identified in fraction 7 from their E1 mass spectra, and the presence of m-and p-phenylphenols was further investigated by comparison of their retention times with authentic standards. However, these isomers were not resolved (Figure lA, peak 31). Certain isomers of this chemical class are direct-acting mutagens of moderate activity (30). Hydroxyxanthene or dihydroxyfluorene and their alkyl-substituted derivatives were tentatively identified in fraction 8 according to their E1 MS and exact mass measurement (198.068), which is clearly different from trimethylnaphthalenecarboxaldehyde (198.104). These compounds were previously identified in diesel exhaust 1444
Envlron. Sci. Technol., Vol. 22, No. 12, 1988
particulates on the basis of HRMS data, but they could not be identified under GC-MS conditions (5). Quinones and Diquinones. Naphthoquinone and a possible fluorenequinone were the only quinones identified in the fractions analyzed. However, several diquinones (phenanthrene/anthraceneand fluoranthene/pyrene) were identified in fraction 7 by direct-probe HRMS, but the higher molecular weight components of this chemical class were not detected under the GC-MS conditions. Nitrogen-Substituted PAH. Two diazaarenes (phenazine and benzo[c]cinnoline) were positively identified in this chemical class. Their E1 mass spectra showed completely different patterns of fragmentation. Whereas M+ and (M - 1)+were the prominent ions for phenazine, M+ and (M - 28)+ were the most abundant for benzo[c]cinnoline. The occurrence of benzo[clcinnoline in diesel exhaust particulates was questioned because of its strikingly similar mass spectrum to %fluorenone (31). In this study, benzo[c]cinnoline was identified on the basis of exact mass measurement (180.068)and coelution with an authentic standard. This compound was also identified in diesel exhaust particulates by using a combination of
200 150 100 50
800 600 LOO 200
01
u C
m
5
6000 A000 2000
n
m
20000
a, > .-
10000
U
rn -
1. 0
a,
0.5
L
0.0 16:OO
36:OO
26:OO
TIME WIN.)
Flgure 2. Reconstructed selected Ion chromatograms of NBS SRM 1650 fraction 7 obtained by GC-NICI MS using methane reagent gas.
I 191
I
k TN0* a,
u C
m
-0
278
c 3
n
rn a,
.-> U
m G)
L
50
100
200
250
300
Flgure 3. Background-substracted direct-probe NICI mass spectrum of NBS SRM 1650 fraction 8 using methane as reagent gas. Compounds identified are ilsted in Table 11.
chromatographic and mass spectrometric techniques (7). Phenazine was identified for the fist time in diesel exhaust particulates. Nitrogen- and Oxygen-ContainingPAC. Hydroxypyrrolidine-2,5-dione, hydroxyphthalimide, and their alkylated derivatives (C, and C,) were tentatively identified for the first time in diesel exhaust particulates (Figure 1). The E1 mass spectrum of hydroxyphthalimide exhibited the molecular ion as base peak with other minor fragments at (M - CO)+, (M - NO)', and (M - CHNO)+. Exact mass measurements agreed with the postulated structures. Although their origin is unknown, they could be derived
from polymeric succinimides which are used as additives of diesel fuel (25). Hydroxyindole and its C1 and C, alkyl derivatives were also identified for the first time in diesel exhaust particulates. Different polar substituted NO,-PAC containing a variety of groups (hydroxy, dihydroxy; quinone, and lactone) and substituted PAC (nitro, hydroxy, and quinone) containing secondary and tertiary nitrogens were tentatively identified by both GC-MS and direct-probe MS. Figure 3 shows a background-subtracted scan obtained on fraction 7 under NICI conditions. Several of these chemical classes were not detected by GC-MS [e.g., hydroxydinitro and Environ. Sci. Technol., Voi. 22, No. 12, 1988
1445
dihydroxynitro (Table II)]. In addition, other polar chemical classes of PAC (nitroaza-,diquinones, nitrodiaza-, and hydroxynitro-) could be detected by GC only as the low molecular weight benzologues (Table I). Several of the identified components are reported for the first time in diesel exhaust particulates (nitrodihydroxy-,nitrolactone-, hydroxyaza-, and azaquinone-PAC). Paputa-Peck et al. (11)reported that some NO2-PAC,HO-PAC, and quinones were not recovered under the GC conditions used, probably because of their low volatilities and/or labilities. Some degradation is also possible under the direct-probe MS conditions used (32))and isomeric compounds cannot be differentiated. Capillary supercritical fluid chromatography (SFC) with a thermionic ionization detector (TIC-1-N2)was used to characterize these same polar fractions using C02at 101 "C (33))and several of the NO2-PACreported in this paper were also identified according to retention times of authentic standards in the previous SFC work. However, the components in fraction 7 were below the detection limits of the SFC technique (33). Triple-quadruple mass spectrometry and mass-analyzed ion kinetic energy spectrometry (MIKES) (34) have been used to detect polar NO2PAC of diesel exhaust particulates. The contribution of polar NO2-PACto the mutagenicity of these fractions is unknown; however, several dihydroxynitropyrenes and hydroxynitropyrenes could be responsible for the high mutagenicities found in these fractions (17). In addition, some nitropyrene lactone isomers that are also strong mutagens may be significant contributors (35).
Acknowledgments We acknowledge the technical assistance of Bruce Jackson in obtaining the HRMS data. Registry No. Hydroxypyrrolidin-2,5-dione,116211-83-7; 116211-84-8; benzoic acid, methyl hydroxypyrrolidin-2,5-dione2 65-85-0;phthalic anhydride, 85-44-9; methylphthalic anhydride, 30140-42-2; hydroxyindole, 69594-78-1; methylhydroxyindole, 116211-85-9;naphthoquinone, 12679-43-5;naphthalenecarboxaldehyde, 30678-61-6; hydroxyphthalimide, 116211-86-0; dinitronaphthalene, 27478-34-8; nitrocinnoline, 116211-87-1; nitroquinoline, 12408-11-6; phenylphenol, 1322-20-9; methylhydroxyphthalimide, 116211-88-2; naphthodiquinone, 11063-25-5; nitrohydroxynaphthalene, 82322-43-8; phenazine, 92-82-0; p phenylphenol, 92-69-3; m-phenylphenol, 580-51-8; naphthalenedicarboxaldehyde, 70848-82-7; naphthalene anhydride, 5343-99-7; nitrobenzoquinone, 3958-76-7; methyl-9-fluorenone, 77468-39-4; benzo[c]cinnoline, 230-17-1; 9-anthrone, 90-44-8; methylhydroxyanthene, 116211-89-3; 1,8-naphthalic anhydride, 81-84-5; methylnaphthalic anhydride, 79075-22-2;nitrochrysene, 6302185-2; benzo[a]fluorenone, 116232-62-3; benzo[b]fluorenone, 82-05-3; dibutyl100647-29-8; 7-H-benz[de]anthracen-7-one, phthalate, 1962-75-0; methyldinitroindene, 116211-91-7; methylnitropyridine, 116211-92-8;nitroindole, 60544-75-4; hydroxynitrobenzothiophene, 116211-93-9; methylnaphthodiquinone, 116211-95-1; nitronaphthoquinone, 80267-67-0; dinitroindene, 116211-96-2; nitrocarbazole, 95273-11-3; methylnitrocarbazole, 116232-63-4; dihydroxynitrobiphenyl, 116211-97-3; hydroxynitrophenanthrene, 116211-98-4; nitrophenanthrene, 68455-92-5; nitrofluoranthene, 77468-36-1; dihydroxynitrophenanthrene, 116211-99-5;methylnitrofluoranthrene, 80182-29-2;hydroxydinitrophenanthrene, 116212-00-1;methylnitrochrysene,80182-33-8; hydroxynitrochrysene, 116212-01-2; dinitropyrene, 78432-19-6; nitrobenzopyrene, 70021-42-0; nitrodiazabenzopyrene,116212-02-3; dipropyl phthalate, 131-16-8.
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(2) Barth, D. S.; Blacker, S. M. J. Air Pollut. Control Assoc. 1978,28, 769-771. (3) Choudhury, D. R.; Doudnev, C. 0. in Health Effects o f Diesel Engine Emissions: Proceedings;Pepelk;; W. E:, Danner, R. M., Clarke, N. A., Eds.; US. Environmental Protection Agency: Cincinnati, OH, 1980; Vol. 1, pp 263-275. Salmeen, I. T.; Pero, A. M.; Zator, R.; Schuetzle, D.; Riley, T. L. Enuiron. Sci. Technol. 1984,18,375-382. Lee, F. S.-C.; Schuetzle, D. in Handbook of Polycyclic Aromatic Hydrocarbons;Bjorseth, A., Ed.; Marcel Dekker: New York, 1983; Chapter 11. Levine, S. P.; Skewes, L. M. J. Chromatogr. 1982, 235, 532-535. Yergey, J. A.; Risby, T. H.; Lestz, S. S. Anal. Chem. 1982, 54,354-357. Yu, M.-L.; Hites, R. A. Anal. Chem. 1981, 53, 951-954. Kaden, D. A.; Hites, R. A.; Thilly, W. G. Cancer Res. 1979, 39,4152-4159. McCann, J.; Choi, E.; Yamasaki, E.; Ames, B. N. Proc. Natl. Acad. Sci. U.S.A. 1975, 72, 5135-5139. Paputa-Peck, M.-C.; Marano, R. S.; Schuetzle, D.; Riley, T. L.; Hampton, C. V.; Prater, T. J.; Skewes, L. M.; Ruehle, P. H.; Bosch, L. C.; Duncun, W. P. Anal. Chem. 1983,55, 1946-1954. Campbell, R. M.; Lee, M. L. Anal. Chem. 1984, 56, 1026-1030. Oehme, M.; Mano, S.; Stray, H. HRC CC, J. High Resolut. Chromatogr. Chromatogr. Commun. 1982,5, 417-423. Robbat, A. J.; Corso, N. P.; Doherty, P. J.; Wolf, M. H. Anal. Chem. 1986,58, 2078-2084. Ramdahl, T.; Urdal, K. Anal. Chem. 1982,54,2256-2260. Newton, D. L.; Erickson, M. D.; Tomer, K. B.; Pellizari, E. D.; Gentry, P.; Zweidinger, R. B. Environ. Sci. Technol. 1982,16,206-213. Schuetzle, D.; Jensen, T. E.; Ball, J. C. Environ. Int. 1985, 11, 169-181. Jensen, T. E.; Schuetzle, D.; Prater, T. J.; Ball, J. C.; Salmeen, I. In Polynuclear Aromatic Hydrocarbons: Mechanisms,Methods,and Metabolism;Cooke, M., Dennis, A. J., Eds.; Battelle: Columbus, OH, 1984; pp 643-661. Woolley, C. L.; Kong, R. C.; Richter, B. E.; Lee, M. L. HRC
CC, J. High Resolut. Chromatogr. Chromatogr. Commun. 1984, 7, 329-332. Richter, B. E.; Kuei, J. C.; Park, N. J.; Crowley, S. J.; Bradshaw, J. S.; Lee, M. L. HRC CC, J. High Resolut. Chromatogr. Chromatogr. Commun. 1983, 6, 371-373. Lee, M. L.; Kuei, J. C.; Adams, N. W.; Tarbet, B. J.; Nishioka, M.; Jones, B. A,; Bradshaw, J. S. J. Chromatogr. 1984,302,303-318. Harrison, A. G. In Chemical Ionization Mass Spectrometry; CRC: Boca Raton, FL; 1986; pp 22-29. Ramdahl, T.; Becker, G.; Bjorseth, A. Environ. Sci. Technol. 1982,16,861-865. Rappaport, S. M.; Wang, Y. Y.; Wei, E. T.; Sawyer, R.; Watkins, B. E.; Rappaport, H. Environ. Sci. Technol. 1980, 14,1505-1509. Hoekman, S. K., Chevron Research Co., Richmond, CA, personal communication, 1986. Goldsmit, B. M. In Carcinogens in Industry and the Environment; Sontag, - J. M., Ed.: Dekker: New York, 1981; pp 281-343. Schulze, J.; Hartung, A.; Kieb, H.; Kraft, J.; Lies, K. H. Chromatographia 1984,19, 391-397. Tong, H. Y.; Sweetman, J. A.; Karasek, F. W.; Jellum, E.; Thorsrud, A. K. J. Chromatogr. 1984, 312, 183-202. Brown, J. P.; Brown, R. J. Mutat. Res. 1979, 63, 1. Erickson, M. D.; Newton, D. L.; Pellizari, E. D.; Tomer, K. B. J. Chromatogr. Sci. 1979,17, 449-454. Schuetzle, D.; Lee, F. S A . ; Prater, T. J.; Tejada, S. B. In
Mutagenicity Testing and Related Analytical Techniques; Frei, R. W., Brinkman, U. A., Eds.; Gordon Breach London, 1981; Vol. 3, pp 193-244. Schuetzle, D.; Riley, T. L.; Prater, T. J.; Harvey, T. M.; Hunt, D. F. Anal. Chem. 1982,54, 265-271.
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(35) Schuetzle, D.,unpublished results, 1986.
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matogr. Chromatogr. Commun. 1986, 9, 161-167. (34) Henderson, T.R.; Sun, J. D.; Royer, R. E.; Clark, Ch. R.; Li, A. P.; Harvey, T. M.; Hunt, D. H.; Fulford, J. E.; Lovette, A. M.; Davidson, W. R. Environ. Sci. Technol. 1983, 17,
443-449.
Received for review December 21,1987. Accepted May 16,1988. This work was supported by the Coordinating Research Council, Project No. CAPE-30.
Organic Photochemistry. 20. A Method for Estimating Gas-Phase Rate Constants for Reactions of Hydroxyl Radicals with Organic Compounds from Their Relative Rates of Reaction with Hydrogen Peroxide under Photolysis in 1,1,2-Trichlorotrifluoroethane Solutiont Wendell L. Dllllng," Stanley J. Gonslor, Glenn U. Boggs, and Celia G. Mendoza
Analytical and Environmental Chemical Research Laboratory, The Dow Chemical Company, Midland, Michigan 48674 The reaction with hydroxyl radicals appears to be the major transformation route for many organic compounds in the atmosphere. To avoid the difficulties of measuring the rate constants for these reactions in the gas phase for some compounds, e.g., those with very low vapor pressures, we have developed a solution-phase system for measuring relative rates. This system involves photolysis of continuously extracted 90% hydrogen peroxide into 1,1,2-trichlorotrifluoroethane solution, which contains two or more organic compounds, one of which serves as a reference standard whose gas-phase rate constant is known. Reasonable correlations (1.2 = 0.84,0.87) were obtained between the relative solution-phaserates and the absolute gas-phase rate constants, which varied over 4 orders of magnitude for n-hexane, 2,2,4-trimethylpentane, cyclohexane, l,l,ltrichloroethane, cyclohexene, trichloroethene, tetrachloroethene, ethyl acetate, toluene, n-propylbenzene, o-xylene, p-isopropyltoluene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, biphenyl, naphthalene, hexafluorobenzene, o-dichlorobenzene, m-dichlorobenzene, 1,2,4-trichlorobenzene, anisole, and nitrobenzene. This method allows estimations of the gas-phase rate constants to within 1 order of magnitude or better. Introduction (2) Numerous organic compounds, such as DDT, PCBs, other chlorinated hydrocarbons, polychlorodibenzodioxins, polycyclic aromatic hydrocarbons, organic acids, etc., with vapor pressures in the 10-12-10-5 Torr range at ambient temperatures have been detected in the troposphere or have been suspected to be present there (3-6). Little information is available on the chemical reactivity of these compounds under tropospheric conditions (7) because of difficulties associated with laboratory gas-phase studies on such compounds (8). The major chemical reaction for many of these compounds in the troposphere appears to be with hydroxyl radicals (HO') (9-11). Knowing the rate constants of these reactions would allow calculation of the transformation rates of these compounds in the atmosphere. To avoid the difficulties of measuring these rate constants in the gas phase for many of these compounds, various workers have suggested calculations or solutionphase rate measurements as alternative methods for est For Part 19 of this series, see ref 1.
* Current address: Central Research-Organic Chemicals and Polymers Laboratory, The Dow Chemical Co., Midland, MI 48674. 0013-936X/88/0922-1447$01.50/0
timating these rate constants. Presently, calculations employing group or substituent constants ( 8 , I I ) are applicable to only a limited number of types of organic compounds. At least two groups (12,13) have reported correlations between gas- and aqueous solution-phase rate constants for the reaction of HO' with a series of organic compounds. Reasonable correlations were obtained that would allow prediction, within ca. 1 order of magnitude for most compounds, of the gas-phase rate constant from the measured solution-phase rate constant. However, water is not a satisfactory solvent for many compounds of interest, such as those noted above, because of their low solubility. We have developed a system for measuring relative rate constants for the reactions of organic compounds with H20z under photolysis in 1,1,2-trichlorotrifluoroethane (CF2C1CFC12,F-113) solution, a satisfactory medium for many compounds of interest. A related method using the same solvent, but not based on relative rate measurements, was reported recently (13). Experimental Section Equipment. Photolyses were performed in a two-compartment reactor shown in Figure 1. The lamp was a standard Hanovia 450-W medium-pressure mercury arc lamp. The photoreactor was connected to the extractor by two 6-mm-i.d. glass tubes, each of which had two 90" bends (as viewed from the top). The extraction of H202 into the F-113 solution and the pumping action were achieved by magnetically stirring the solution in the extractor with a Star Head Teflon-coated magnetic stirring bar. The outlet and inlet tubes on the extractor were offset so that the stirring action forced the solution out the lower tube and back into the extractor from the upper tube. Stirring was maintained at the highest allowable rate that did not form droplets of 90% H202that would be swept out of the extractor. This resulted in a flow rate of - 5 cm38. The extractor and connecting tubes were covered with black tape to minimize light penetration into the 90% aqueous HzOzlayer. The entire apparatus was immersed up to the reaction solution level in a refrigerated constant-temperature bath maintained at 25.0 f 0.1 "C. Materials. HzOzsolutions (go%,FMC Corp., and 30%, VWR Scientific Chemical Reagent) were used as received. Assays by the permanganate method (14) gave values of 90.47 f 0.19% and 29.91 f 0.11%, respectively. All organic test compounds were commercial samples and were used as received. Gas chromatographic (GC)
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