Anal. Chem. 1984, 56, 1329-1335
LITERATURE CITED Nlmz, H. H.; Ludemann, H . 4 . Holzfofschung 1978, 30, 33. Nimz, H. H.; Robert, D.; Falx, 0.; Nemr, M. Holzforschung 1981, 3 5 , 16. Maclel, G. E.; O’Donnell. D. J.; Ackerman, J. J. H.; Hawkins, B. H.; Bartuska, V. J. Makromol. Chem. 1981, 182. 2297. Yannoni, C. S. Acc. Chem. Res. 1982, 15, 201. Wasyllshen, R. E.; Fyfe, C. A. Annu. Rep. NMR Spectrosc. 1982, 72, 1. Gersteln, B. C. Anal. Chem. 1983, 5 5 , 781A. Gersteln, B. C. Anal. Chem. 1983, 5 5 , 899A. Kolodzlejskl, W.; Frey, J. S.; Maciel, G. E. Anal. Chem. 1982, 5 4 , 1419. Atalla, R. H.; Gast, J. C.; Sindorf, D. W.; Bartuska, V. J.; Maciel, G. E. J. Am. Chem. SOC.1980, 102, 3249. Earl, W. L.; VanderHart, D. L. J. Am. Chem. SOC.1980, 102, 3251. Maciel, G. E.; Kolodziejski, W. L.; Bertran, M. S.;Dale, B. E. Macromolecules 1982, 15, 686. Earl, W. L.; VanderHart, D. L. Macromolecules 1981, 14, 570. Dudley, R. L.; Fyfe, C. A,; Stephenson, P. J.; Deslandes, Y.; Hamer, G. K.; Marchessault, R. H. J. Am. Chem. SOC.1983, 105, 2469. VanderHart, D. L.; Atalla, R. H. Macromolecules, In press. Horii, F.; Hirai, A.; Kitamaru, R. Polym. Bull. 1982, 8 , 163. Bartuska, V. J.; Maciel, G. E.; Bolker, H. I.; Fleming, B. I. Holzforschung 1980, 3 4 , 214. Schaefer, J.; Sefcik, M. D.; SteJskal, E. 0.; McKay, R. A,; Hall, P. L. Macromolecules 1981, 14, 557. “Analysis of Blsulfite Cooking Liquor”; TAPPI Standard, 1945, No. T604.
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(19) “Permanganate Number of Pulp”; TAPPI Standard, 1971, No. T214. (20) ”Kappa Number of Pulp”; TAPPI Standard 1976, No. T236. (21) Rydholm, S. A. “Pulplng Processes”; Interscience: New York, 1965; pp 739-744. (22) Rydholm, S. A. “Pulping Processes”; Interscience: New York, 1965; p 1113. (23) Taylor, M. G.; Deslandes, Y.; Bluhm, T.; Marchessault, R. H.; Vincendon, M.; Saint-Germain, J. Tappl 1983, 66 (6), 92. (24) Browning, 8. L. “The Chemlstry of Wood”; R. E. Krieger Publishing Co.: Huntington, NY, 1975; p 256. (25) Browning, B. L. “The Chemlstry of Wood”; R. E. Krleger Publishing Co.: Huntington, NY, 1975; pp 65, 67. (26) Brownlng, B. L. “The Chemistry of Wood”; R. E. Krieger Publishing Co.: Huntington, NY, 1975; p 197. (27) Freudenberg, K.; Nelsh, A. C. “Constitution and Biosynthesis Of Lignin”; Sprlnger-Verlag: New York, 1968; p 70. (28) Rydholm, S. A. “Pulping Processes”; Intersclence: New York, 1965; p 167. (29) Rydholm, S. A. “Pulping Processes”; Interscience: New York, 1965; pp 359-360. (30) Brownlng, 6. L. “The Chemlstry of Wood”; R. E. Krieger Publishing Co.: Huntington, NY, 1975; p 457. (31) Grler, J. Holzforschung 1982, 36,43. (32) Grier, J. Holzforschung 1982, 3 6 , 456-460.
RECEIVED for review August 1, 1983. Accepted March 1,1984. The authors gratefully acknowledge partial support of this research by the Colorado State University Experiment Station.
Determination of Atmospheric Degradation Products of Toluene by Tandem Mass Spectrometry Robert J. O’Brien* and Bruce E. Dumdei Chemistry Department and Environmental Sciences Doctoral Program, Portland State University, Portland, Oregon 97207 Susan V. Hummel and Richard A. Yost Chemistry Department, University of Florida, Gainesville, Florida 32611
Atmospherlc oxldatlon of toluene, an Important constltuenl of polluted air, produces a complex array of products which have never been adequately characterlred. Normal toluene and two deuterium labeled forms have been subjected to slmulaled atmospherlc oxldatlon. The products of the oxldatlon were separated and ldentlfled by triple quadrupole mass spectrometry (MSIMS) uslng a dlrect probe Inlet. Deuterium labellng Improves the signal to background ratlo for the trace amounts of the compounds which were available and allows the fragmentatlon patterns to be more clearly Interpreted.
Toluene is an important constituent of polluted atmospheres, as it is one of the most abundant components of gasoline and is widely used in solvents. In contrast to the alkanes and alkenes, the atmospheric chemistry of toluene and the other benzene derivatives represents a last major unknown area of urban atmospheric chemistry ( I ) . Chemical processes occurring in sunlit, polluted atmospheres are usually simulated in so-called smog chambers. Hydrocarbons and oxides of nitrogen in the parts-per-billion to parts-per-million range in air are exposed to real or simulated sunlight and the products of the reaction are determined by a variety of analytical techniques, usually gas chromatography (GC) for the hydrocarbons and their oxidation
products. This procedure has been successfully applied to the alkenes and alkanes (e.g., ref 2). For the aromatic hydrocarbons, toluene has received the most study but very few products have been found by GC analysis. Several studies have been published in which a partial characterization of toluene’s oxidation products has been carried out (3-1 3). These studies have normally used gas-phase sampling, with concentration of the sample by a cold trap or absorptive cartridge such as Tenax. In one case (7) suspended aerosols were collected by filtration and extracted from the filter with solvents. Separation and identification of the products have been carried out by using GC or GC combined with mass spectrometry (GC/MS). The chief gas-phase products identified were peroxyacetyl nitrate (PAN), benzaIdehyde,cresol and nitrotoluene isomers, CO, and COz, but their combined yields are half or less of the reacted toluene. Many of the prior studies (6,8-11,13) have employed high concentrations of reactants (toluene and oxides of nitrogen) in order to increase the amount of products formed. This is somewhat counterproductive since a high concentration of nitrogen oxides favors radical termination processes to produce various nitro aromatics and aryl nitrates. These products are relatively easy to characterize by gas chromatography but their yield at ambient levels of nitrogen oxides is negligible. The products of major interest are the ring-fragmentation species, produced by attack of atmospheric hydroxyl radical on tolu-
0003-2700/84/0356-1329$01.50/00 1984 Amerlcan Chemlcal Society
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ANALYTICAL CHEMISTRY, VOL. 56, NO. 8, JULY 1984
0' 0
6
IO
16
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TUIE M C )
Figure 1. Time profile of daughter ions of solid probe insertion.
m / z 99 parent, following
ene, followed by addition of atmospheric oxygen, and subsequent extensive rearrangement and fragmentation. Recently, we have demonstrated that a major reason for the failure to detect the bulk of these products is their precipitation from the gas phase to the readion vessel walls (14). Currently, quantitative gas-phase product data are available for PAN, CO, benzaldehyde, cresols, some nitro aromatics, and for photooxidation of NO to NOz with accompanying O3 formation (3). In addition, several ring-fragmentation products have been identified in various studies but never quantified (6).This information, along with several hypothesized products, has been used to develop explicit mechanisms (3, 15) for the atmospheric oxidation of toluene as carried out in smog chambers. However, the hypothetical nature of these chemical mechanisms can only be removed by identification and ultimate quantification of the intermediate reaction products. The general field of tandem mass spectrometry has been reviewed (16,17). This paper describes a methodology for the identification of environmental degradation products using MS/MS in conjunction with isotopic labeling. Although analysis of unknowns in complex mixtures is considered to be a major capability of MS/MS, a limited number of applications have been published to date. The samples analyzed here constitute complex mixtures of unknowns, although considerable information about compound classes and some specific compounds was available.
EXPERIMENTAL SECTION Reagents. All chemicals were reagent grade. Methanol and dichloromethane solvents were further purified by fractional toluene (99.5% D)was obdistillation. Methyl-deuterated (D3) tained from Stohlet Isotope Chemicals, Rutherford, NJ. Pertoluene (99.5% D) was obtained from KOR deuterated (Ds) Isotopes, Cambridge,MA. Nitric oxide (99%) was from Matheson. Zero-air (
