MS/MS Analysis of the Products of Toluene Photooxidation and Measurement of Their Mutagenic Activity

Products of the photooxidation of toluene from an irradiated 5.1 ppm toluene/0.9 ppm NO_x mixture were identified by use of a triple-quadrupole MS/MS operated in an atmospheric pressure ionization mode. The reaction was carried out in a flow-mode 22.7-m³Telfon smog chamber. The steady-state reactant and product mixture was continuously transferred to the mass spectrometer inlet at 144 L/min. By using structurally similar standards, semiquantitative MS/MS analyses for many of the ring fragmentation products were conducted. Quantitative analyses by chromatographic methods and semiquantitative analyses by MS/MS were conducted for a variety of ring fragmentation products. The following products were found with yields of 1% (C/C) or greater: methylglyoxal, glyoxal, benzaldehyde, methylbutenedial, hydroxy-methylbutenedial, peroxyacetyl nitrate, oxoheptadienal, CH₃COOH, HCHO, hexadienal, and hydroxyoxo-heptadienal. The sum of the yields of all products measured was ̴60%, assuming a total cresol yield of 16%. Several ring fragmentation products that have not been previously detected were identified in this study. Mechanisms are described for some major product pathways. The mutagenic activity of the steady-state product mixture was measured by using the Ames assay Salmonella typhimurium strain TA 100. The mutagenic activity data are discussed relative to our earlier findings (10) that resulted from different reaction conditions.