570 Anal. Chem. 1982, 54, 570-574

in the consumption of an impossibly large number of electrons. They suggest that such responses with the dc ECD are due to complex negative-ion migration and space-charge effects rather than with the stoichiometry of the EC reaction. While most of their work in this area has been with the dc ECD, this group recently suggested (16) that these nonclassical forces may also effect responses observed with the pulsed modes. While it seems quite possible that the responses observed with a pulsed ECD may be somewhat dependent on such physical effects, it would not seem appropriate to invoke these sec- ondary effects to explain the results reported here. In our measurements, response differences among various compounds have been observed under identical physical conditions of the detector. It seems most likely, therefore, that the differences reported here between CH31 and CFC13, for example, are due to differences in the nature of their electron capture reactions.

In conclusion, we have reported here the nature of the ECD responses of several halogenated methanes and have found that for the case of CH31 responses cannot be explained by the classical dissociative electron capture mechanism, alone. We are presently examining the ECD responses of other types of strongly responding compounds. It seems likely that some of these might also exhibit behavior which deviates from the classical EC mechanisms. A practical application of this work is to find functional groups which provide both increased sensitivity and ease of quantitation over the entire dynamic range. From the work reported here, the iodide functionality appears to be of this favorable type. Unfortunately, iodide derivatives are often thermally unstable and may not pass

quantitatively through many chromatographic systems. Also, as shown here, the most favorable response characteristics of CH31 were observed with a detector temperature which would be too low for general organic analysis. It seems quite possible, however, that other functional groups will be discovered which possess greater thermal stability and react in accordance with the CH31 mechanism at higher detector temperatures.

LITERATURE CITED Lovelock, J. E. Anal. Chem. 1963, 35, 474. Wentworth, W. E.; Chen, E. J . Gas Chromatogr. 1967, 5 , 170. Fenlmore, D. C.; Davls, C. M. J . Chromatogr. Sci. 1970, 8 , 519. Maggs, R. J.; Joynes, P. L.; Davles, A. J.; Lovelock, J. E. Anal. Chem. 1971, 43 , 1966. Sullivan, J. J.; Burgett, C. A. Chromatographi8 1975, 8 , 178. Lovelock, J. E.; Watson, A. J. J . Chromatogr. 1978, 158, 123. Grimsrud, E. P.; Klm, S. H. Anal. Chem. 1979, 51, 537. Chrlstophorou, L. G. Chem. Rev. 1976, 76, 409. Blondl, M. A. "Defense Nuclear Agency Reaction Rate Handbook"; Bortner, M. H., Baurer, T., Eds., 1975; Chapter 16, p 16. Gobby, P. L.; Grimsrud, E. P.; Warden, S. W. Anal. Chem. 1980, 52, 473. Slegel, M. W.; Fib, W. L. J . Phys. Chem. 1976, 80, 2871. Rosenttock, H. M.; Draxl, K.; Stelner, 8. W.; Herron, J. T. J . Phys. Chem. Ref. Data 1977, 6 , 742. Schexnayder, C. J. NASA Tech. Note 1963, 01791. Frost, D. C.; McDowell, C. A. J . Chem. Phys. 1958, 29, 503. Aue. W. A.; Kaplla, S. J . Chromatogr. 1980, 188, 1. Kapila, S.; Vost, C. A.; Aue. W. A. J . Chromatogr. 1980. 196, 397.

RECEIVED for review September 21,1981. Accepted December 8,1981. Acknowledgment is made to the National Science Foundation for support of this research under Grant No. CHE-7824515.

Mass Spectral Characterization of Nitrogen-Containing Compounds with Ammonia Chemical Ionization

Michelle V. Buchanan

Analytical Chemistry Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830

Chernlcal Ionization mass spectrometry using ammonia and ammonla-d, as reagent gases is used to differentlate nltro- gentontalnlng compounds, including amlne-substituted poly- cyclic aromatic hydrocarbons and araarenes, as well as compounds contalnlng two nltrogen atoms. Thls technique Is used to characterlre two alkaline fractlons of a coal-derlved llquld by comblned gas chromatography/mass spectrometry.

Previous work in these laboratories and elsewhere (1,2) has shown that nitrogen-containing aromatic compounds in coal- and shale-derived petroleum substitutes are responsible, a t least in part, for the overall higher bacterial mutagenicity of these materials relative to petroleum liquids. The biological activity of these nitrogen-containing aromatic compounds has been shown (3) to vary significantly with the degree of sub- stitution at the nitrogen atom. For example, primary aromatic amines exhibit greater bacterial mutagenic activity than azaarenes. Thus, determining the type of nitrogen-containing species present is important in the overall assessment of these materials with respect to mutagenic activity.

Determining the degree of substitution of an amine in a complex mixture is difficult. Combined gas chromatogra- phy/mass spectrometry can be used to obtain mass spectra of chromatographically separated compounds. However, the

electron impact mass spectra of isomeric primary, secondary, and tertiary aromatic amines and azaarenes are virtually identical. For example, the tertiary amine N,N-dimethyl- aminonaphthalene and the primary amine 1-amino-4-ethyl- naphthalene both yield mass spectra with prominent molec- ular ions at m/z 157, with little or no additional fragmentation which would differentiate the two compounds. Often, prior to mass spectral characterization, mixtures of nitrogen-con- taining compounds are chemically treated to form tri- methylsilyl or trifluoromethylacetyl derivatives (4,5). Primary and secondary amines, which derivatize, can then be distin- guished by use of electron impact ionization from the tertiary amines and azaarenes, which do not derivatize. However, isomeric primary and secondary amines are not easily dis- tinguished using this method.

To provide a direct analysis of these nitrogen-containing compounds, without derivatization, chemical ionization (CI) mass spectrometry has been employed using ammonia and its deuterated analogue, ammonia-d3, as reagent gases. The differentiation of simple aliphatic and aromatic amines using ammonia CI was demonstrated by Hunt et al. (6). The amines are ionized by transfer of a hydrogen ion from the ammonium ion to the more basic amine

R,,NH, + NH4+ + [R3-nNHn+l]+ + NH3

where n may be zero, one, or two, corresponding to a tertiary,

0003-2700/82/0354-0570$01.25/0 0 1982 American Chemical Soclety

r- ,

ANALYTICAL CHEMISTRY, VOL. 54, NO. 3, MARCH 1982 5;ri

5 IO IS 20 25 30 35 40

220 235 250 265 280

TIME (min)

Figure 1. A gas chromatogram of the ether-soluble base fraction of Coal Oil 1202. See Table 11.

secondary, or primary amine, respectively. If ammonia-d3 is used as the ionization reagent, not only is the amine ionized by the transfer of a deuterium ion but the hydrogen atoms on the nitrogen exchange with the deuterium atoms of the ammonia as well

Thus, the resulting deuterated ion exhibits a change in mass from the NH3 C1: mass spectrum of one, two, or three mass units, indicating that the compound is a tertiary, secondary, or primary amine, respectively. In this study, this technique has been extended to the analyses of amine-substituted po- lycyclic aromatic hydrocarbons, azaarenes, and compounds containing two nitrogen atoms. Two alkaline subfractions of a coal-derived liquid have also been characterized using am- monia CI mass spectrometry.

EXPERIMENTAL SECTION Mass spectra were obtained with a Hewlett-Packard 5985A gas

chromatograph/mass spectrometer equipped with a dual EI/CI source. Chemical ionization spectra were obtained twice, oncle with ammonia and then with ammonia-d3. Ammonia-d3 (99 atom % deuterium) was obtained from Merck & Co., Inc., Teterboro, NJ. The ammonia reagent gases were used at an ion source pressure of 0.15-0.25 torr at 200 "C and 200 eV and were intro- duced via the direct insertion probe.

The gas chromatograph interfaced to the mass spectrometer was equipped with a 25-m fused silica open tubular column coated with SE-52, obtained from J&W Scientific, Inc., Orangeval, CA. Helium was used as the canier gas at 1.5 kg/cm2 head pressure. The inlet and GC/MS transfer lines were held at 280 "C. The column oven was hleld at 100 "C for 5 min and then programmed to 280 "C at a rate of 2 OC/min. A splitless injector was used to introduce the sample.

Standard amines and azaarenes were obtained commercially and used as received. Cod Oil 1202 was supplied through the USEPA/DOE Synfuels Research Materials Facility (7) for re- search into the chemical and biological properties of petroleum substitutes. This coal oil is identified by a repository number to underscore the fact that it is a discrete sample and not nec- essarily representative of the technology as a whole. The coal oil was fractionated as described previously (8) to yield an eth- er-soluble base fraction. The ether-soluble bases were separated further to isolate the mutagenic compounds in an "acetone subfraction" (1, 9).

RESULTS AND DISCUSSION A number of standard compounds are listed in Table I,

along with the base peaks observed in the CI mass spectra of each compound when ionized by ammonia and ammonia-d3

Table I. Nitrogen-Containing #Compounds

NH,/ND, CI Mass Spectra of

m/z, m/z degree of mol NH, ND, substi-

compound wt CI CI tution Amines

aniline 93 94 97 1" 2-aminobiphenyl 169 170 173 1" 1-aminonaphthalene 143 144 147 1" 1-aminoanthracene 193 194 197 1" 1-aminopyrene 217 218 221 1' N-ethylaniline 121 122 124 2" diphenylamine 169 170 172 2" N-methylaminoanthra- 237 238 240 2"

N,N-dimethylaniline 1 2 1 122 123 3" triphenylamine 245 246 247 3"

quinoline 129 130 131 3" acridine 179 180 181 3" carbazole 167 168 170 3"

Compounds Containing Two Nitrogens 5-aminoquinoline 144 145 148 1" t 3" 1-aminoacridine 194 195 198 1" t 3" phenazine 180 181 182 3" t 3" 0-tolidine 212 213 218 1" t 1" 1,4-diaminoanthra- 238 239 244 1" t 1"

quinone

Azaarenes

quinone

In the case of the five primary aromatic amines, the change in mass observed in going from the NH3 CI to ND3 CI spectra is three, indicating the addition of one deuterium to the ni- trogen atom as well as the exchange of the two amine hydrogein atoms with the deuterium atoms of the ND4+. The NH3/ND13 CI mass spectra of the secondary amines, N-ethylaniline, diphenylamine, and N-methylaminoanthraquinone, yield the expected change of two mass units, with one deuterium added through ionization and one exchanged. The tertiary amines Nfl-dimethylaniline and triphenylamine have no exchange- able hydrogens, and thus exhibit only a change of one mass unit due to ionization. From these data, it can be seen that isomeric aromatic amines can be differentiated using this technique. For example, aminobiphenyl (primary) and di- phenylamine (secondary), both with molecular weights of 1691, are readily distinguished using NH3/ND3 CI with changes in mass of three and two mass units, respectively. The NH3/ND3 CI spectra of N-ethylnniline and NJV-dimethylaniline (both with molecular weights of 121) can be used to assign these compounds as secondary and tertiary amines, respectively.

572

Table 11. Peak Identification of Gas Chromatograms of Ether-Soluble Bases of Coal Oil 1202

ANALYTICAL CHEMISTRY, VOL. 54, NO. 3, MARCH 1982

no. of alkyl carbons

anilines 2 3 4

0 aminoindanes

2 4

N-alkyl aminoindanes 1 2 3 4

pyridines 5 6 7 8

1 2 3 4 5 6 7

3 4 5 6

0

azaindanes

azaindenes

quinolines

2 3 4 5 6

0 1 2 3 4 5

phenyl pyridines

peak no. no. of alkyl carbons Primary Aromatic Amines

aminonaphthalenes 1, 2 0 5; 6 1 9,lO aminoanthracenes

6, 14 5, 8 17, 18, 22 22, 24

2

2 aminofluoranthenes

Secondary Aromatic Amines N-alkyl aminonaphthalenes

9, 11, 13, 15 1 14, 15, 19 20-22 29

Azaarenes

2 8 20 20

3 3, 6, 8, 10, 14 7, 10-14, 16 9, 12, 14, 15, 17, 18 17, 20, 21, 24, 25, 27 23 42

10, 25 23, 26-28, 34 25, 29, 31, 32 34

4 7,9,11 11-14, 16,18 17 , 19-22 19, 20, 23, 25 27-29, 31 40

24, 25 25, 26, 28, 30, 32, 34 29, 32, 36-39 39, 41, 43 43,45 57

Heterocyclic compounds can also be characterized with this technique. When the azaarenes quinoline and acridine are ionized with ND4+, they yield ions with are one mass unit greater than when ionized with NH4+. These mass spectra are expected for tertiary amines which have no hydrogens attached to the nitrogen atom. Another heterocyclic com- pound, carbazole, yields a change of mass of two units upon analysis, corresponding to a secondary amine with its one active hydrogen.

One limitation of the NH3/ND3 CI method is that it cannot discern whether a compound which gives a change of one or two mass units is a heterocyclic aromatic or an amine-sub- stituted aromatic compound. For example, both trimethyl- pyridine and N,N-dimethylaniline would yield a change of one mass unit, indicative of tertiary substitution. Additional information would be necessary for the final classification of these compounds. For example, although conventional electron ionization of these two compounds yields similar spectra, some differences can be observed. The spectrum of

azaphenylnaphthalenes 1 2 3 4 5

0 1 2 3 4 5

3 4 5 6

0 1 2 3 4 5

1 2 3 4

0 1

0

benzoquinolines

azafluorenes

azapyrenes

dibenzoquinolines

azabenzop yrenes

azaanthanthrenes

peak no.

21 24, 25

43

40, 57, 60

32

45, 46, 50 48, 53 52-56, 59 59,60 60, 62, 64

32, 33 38, 39 40, 42, 44 47 50 52, 56, 57

45 45-49 49,53 54

47 49-52 52-54, 56, 57 57, 58, 60 62, 64, 65 65, 66

61,62 62-67 65-67 68

66,67 68,69

70

the substituted pyridine shows a larger abundance of C6H7N+, due to cleavage of the alkyl group from the ring, than that of the substituted aniline. The substituted aniline, on the other hand, undergoes cleavage of the substituted amine group from the ring to yield C6H6+.

A series of compounds which contain two nitrogen atoms was also studied. None of these compounds yield any doubly charged species, (M + 2)/2, in the CI spectra corresponding to ionization a t both nitrogen atoms. The diamino com- pounds, tolidine (3,3’-dimethyL4,4’-diarninobiphenyl) and 1,4-diaminoanthraquinone (both amine groups are primary) yield NH3 CI spectra at masses corresponding to the molecular weight of the compound plus one mass unit, M + 1, resulting from the addition of one hydrogen ion. The ND3 CI spectra of these compounds yield ions which are five mass units greater than those observed in the NH3 CI spectrum. This change of five mass units arises from the addition of one deuterium atom to one of the nitrogen atoms and exchange of all four hydrogens on the two nitrogen atoms. Phenazine

ANALYTICAL CHEMISTRY, VOL. 54, NO. 3, MARCH 1982 57:3

11

TIME ( r n l n l 10 15 x ) 25 30 35 40 45 50 55 60 65

115 130 145 160 175 190 205 220 235 250 265 280

I I I I I I - 1 1 1 I I I

Figure 2. Gas chromatogram of the acetone subfraction of the ether-soluble base from Coal Oil '1202. See Table 111.

(9,lO-diazaanthracene), which contains two nitrogens within the aromatic ring system, exhibits a ND3 CI spectrum which is only one mass unit grleater than the NH3 CI spectrum, corresponding to ionization of one nitrogen and no hydro- gen/deuterium exchange. The mixed amine-azaarenes, am- inoacridine and runinoquinoline, yield ND3 CI spectra which are three mass units greater than the NH3 CI spectra. This corresponds to the ionization at one of the nitrogen atoms and exchange of both hydrogens on the amine nitrogen. It was not possible using these data to discern whether the ring nitrogen or the amine nitrogen is ionized. However, this should not hinder the assignment of the types of nitrogen atoms present in the compound. Knowing the molecular formula for the compounid and the change in mass in going from NH, CI to ND, CI, it, would follow that one tertiary and one primary amine nitrogen are present.

The NH3/ND3 CI technique was used to identify the type of compounds present in two basic fractions of a coal-derived liquid, Coal Oil E!02 (7). The gas chromatographic profiles of the ether-soluble fraction (ESB) and the acetone subfraction of the ESB are given in Figures 1 and 2, respectively. The compounds identified in these two fractions are listed in Tables I1 and 111. The ESB and the acetone subfraction contain several hundred components and thus, the gas chro- matographic profiles of these two samples contain poorly resolved peaks, even when a high-resolution wall-coated open tubular column is used. Because these unresolved compounds each yield a number of fragment ions, the electron impact mass spectra obtained from this sample are not easily inter- preted. The ammonia CI mass spectrum of an amine usually exhibits only the protonated molecular ion, with little or no fragment ions. Thus, the unresolved compounds in a chro- matographic peak may be more readily identified in the sim- pler NH8/ND3 C1 mass spectra. For example, peak 25 in Figure 1 was found to contain at least five compounds, in- cluding C1 aminonaphthalene, C3 and C5 azaindene, C4 quinoline, and C5 azaindane, where C, denotes the number (n) of carbons in the alkyl substituents.

Both the ESB tand its acetone subfraction contain terti- ary-type amines. However, as discussed previously, a tertiary aromatic amine and an azaarene cannot be distinguished using NH3/ND3 CI, unless additional information is obtained. In the case of the alcetone subfraction, previous work using standard compounds (7) hm shown that the separation of the acetone subfraction excludes tertiary aromatic amines from this subfraction. 'rhus, the compounds exhibiting a change of one mass unit in the acetone subfraction can be identified as azaarenes. However, this argument cannot be used in the

Table 111. Peak Idenr.ification of Gas Chromatograms of Acetone Subfraction of 1202

no. of alkyl carbons

anilines 2 3 4 5

indanes 0 1 2 3 4

indenes 3 4 5

amino-

amino-

phenyl- pyridines 2

azaphenyl- naphthalenes 0

2 benzo-

quinolines 0 1 2

no. of peak no. alkyl carbons

Primary Aromatic Amines amino-

1, 2 naphthalenes 3-5 0 6-9 1 10, 12-24 2

3 amino-

7 biphenyls 9-14 0 9, 13-15, 17-20 1 19-23 2 25 amino-

fluorenes 0

2 2 , 2 3 1 25, 27 2 29 amino-

anthracenes 1 n B

Azaarenes azapyrenes

0 21 1

2 3

3 3 , 3 5 dibenzo- 37 quinolines 44 1

azabenzo- pyrenes

28 0 30, 31 1 32. 33

peak no.

16, 17 21-23 24, 26 29-30

25, 27 30 35

29, 31 33, 34 36

32 44

35, 36 38-41 42-44 4 5 , 4 6

47-49

50 51

case of the original ESB. Most of the compounds in the ESB are tertiary type. If it is assumed that all of these compounds are azaarenes, the compounds may be assigned as listed in Table 11. From this table it can be seen that except for the one- and two-ring compounds, all of the tertiary type com- pounds in the ESB fall within a homologous series of alkyl- substituted azaarenes, which begin with the unsubstituted parent azaarene. The compounds identified as Cot C1, or Cz substituted azaarenes may be assigned unambiguously because there are no corresponding isomeric tertiary amines. For example, NJV-dimethylaminonaphthalene has the same mo-

574 Anal. Chem. 1902, 54, 574-578

lecular weight (171) as C3 quinoline, but no tertiary amine substituted naphthalenes exist which correspond to Co, C1, and Cz substituted quinolines, which have molecular weights of 129, 143, and 157, respectively. However, from the C3 substituted azaarene and beyond, there is a possibility of tertiary aromatic amines being present as well as azaarenes. Thus, these assignments cannot be made with certainty.

Both the ESB and the acetone subfraction contained pri- mary aromatic amines (PAAs). There were more kinds of PAAs detected in the acetone subfraction than in the original ESB as was intended (1,9) by the separation procedure used. Secondary aromatic amines were only detected in the ESB fraction. As in the case of the tertiary-type amines, it is not possible to assign these conclusively as either heterocyclic or amine-substituted aromatics.

The NH3/ND3 CI technique has been shown to be useful in the mass spectral analysis of primary, secondary, and tertiary amine substituted aromatics as well as nitrogen heterocycles in complex samples. Heterocyclic nitrogen compounds cannot be unambiguously distinguished from amines using NH3/ND3 CI, unless additional information is obtained from either the sample history or other spectroscopic techniques.

An additional feature of the NH3/ND3 CI technique is that only compounds with proton affinities greater than NH4+ (207 kcal/mol) are ionized; thus this technique can be used to characterize nitrogen-containing compounds in the presence of other types of compounds in a mixture (including-OH and -SH substituted) without interference (10).

ACKNOWLEDGMENT The author thanks C.-h. Ho for providing the two alkaline

fractions, G. Olerich for technical assistance, and M. R. Guerin for helpful discussions concerning this work.

LITERATURE CITED (1) Guerln, M. R.; Ho, C.-h.; Rao, T. K.; Epler, J. L. Environ. Res. 1980,

23, 42. (2) Wilson, B. W.; Peterson, M. R.; Pelroy, R. A,; Cresto, J. T.. Fuel 1981,

60, 289. (3) Ho, C.-h.; Clark, B. R.; Guerin, M. R.; Barkenbus, 8. D.; Rao, T. K.;

Epler, J. L. Mufat. Res. 1981, 85, 335. (4) Pierce, A. E. "Sllylation of Organic Compounds"; Pierce Chemical Co.:

Rockford, IL, 1968; p 39. (5) Blau. K.: Kina, G. S. "Derivatives for Chromatoarauhv": Hevden: Lon- . . .

don, 1978; 639. (6) Hunt, D. E.; McEuen, C. N.; Upham, R. A. Tetrahedron Left. 1971, 47 ,

4539. (7) &lest, W. H.; Coffin, D. L.; Guerin, M. R. "Fossil Fuels Research Matrix

Program", ORNLITM-7345; Oak Ridge National Laboratory: Oak Ridge, TN, 1980.

(8) Rubln, I. B.; Guerln, M. R.; Hardlgree, A. A.; Epler, J. L. Environ. Res. 1978, 12, 358.

(9) Ho. C.-h.; Guerin, M. R.; Clark, B. R.: Rao, T. K.; b i e r , J. L. J . Anal. Toxicol. 1981, 5, 143.

( I O ) Buchanan, M. V.; Ho, C.-h.; Clark, B. R.; Guerin, M. R. In "Polycyclic Aromatic Hydrocarbons"; Cook, M., Dennis, A. J., Eds.; Battelle Press: Columbus, OH, 1981; Vol. 5, pp 133-144.

Toxicol. 1981, 5, 143. ( I O ) Buchanan, M. V.; Ho, C.-h.; Clark, B. R.; Guerin, M. R. In "Polycyclic

Aromatic Hydrocarbons"; Cook, M., Dennis, A. J., Eds.; Battelle Press: Columbus, OH, 1981; Vol. 5, pp 133-144.

RECEIVED for review October 7, 1981. Accepted November 16, 1981. Research sponsored by the Office of Health and Environmental Research, United States Department of Energy under Contract W-7405-eng-26 with the Union Carbide Corporation.

Determination of Organosulfur Compounds in Hydrocarbon Matrices by Collision Activated Dissociation Mass Spectrometry

Donald F. Hunt* and Jeffrey Shabanowltz

DepartmenP of Chemistry, University of Virginia, Charlottesviile, Virginia 2290 1

Collldon activated dlssoclatlon mass spectra of (M + 1)' Ions from 33 organosulfur compounds are presented. Ions re- sultlng from loss of the radlcal HS. are promlnent In the spectra of thlophenols, dlthlenyls, trlthlenyls, and dlbenro- thlophene derlvatlves but not In the spectra of allphatlc sul- fldes or hlghly alkylated thiophenes. Use of 33 amu neutral loss scans on a trlple quadrupole mass spectrometer for the analysts of organosulfur compounds In crude petroleum dls- tlllates Is descrlbed. Total time per sample for thls analysis Is under 20 mln. Qualltatlve dlfferences In the spectra of several crude 011 samples are readlly apparent. Prellmlnary results from colllslon activated dlssoclatlon of (M + NO)' Ions In the nltrlc oxide chemlcal lonlzatlon mass spectra of all- phatlc sulfones are descrlbed.

Potential shortages of high-quality crude petroleum that can be easily processed as fuel have prompted investigations into alternate energy sources such as heavy petroleum dis- tillates, coal liquids, shale oil, and oil from tar sands. Detailed knowledge of the chemical components present in these ma- terials is necessary in order to ensure that the most effective, efficient and environmentally safe methods are chosen for production, storage, and processing of these valuable resources. Monitoring organosulfur compounds during fuel production

0003-2700/82/0354-0574$0 1.2510

is important since many of these compounds poison the catalysts used in the processing steps, several of the sulfur heterocycles are suspected mutagens and/or carcinogens ( I ) , and toxic gases such as H2S and SOz are liberated during utilization of fuels rich in sulfur-containing components.

Analytical methods for characterizing sulfur compounds in coal liquids, shale oil, and crude petroleum currently involve extensive fractionation of the sample by a combination of distillation, extraction, and chromatographic steps followed by analysis with either a gas chromatograph/mass spectrom- eter system (2-5) or a double focusing mass spectrometer operated under low voltage E1 (12 f 0.2 eV) conditions a t a resolution in excess of 50000 (6,7). Gas chromatography/mass spectrometry is ideally suited for the identification of specific structural isomers in highly fractionated samples but is too time-consuming for routine characterization of complex pe- troleum matrices. In contrast, direct analysis of petroleum feedstock or coal liquefaction products by low-voltage elec- tron-impact, high-resolution mass spectrometry can be ac- complished relatively quickly and affords a wealth of infor- mation about the elemental composition, molecular weight, and carbon number of the mixture components. This method affords excellent results for hydrocarbon matrices rich in compounds containing the elements C, H, N, and 0 but is much less satisfactory for characterizing mixtures rich in sulfur compounds. In this situation extremely high resolving power,

0 1982 American Chemical Society