NEGATIVE-ION LASER-DESORPTION IONIZATION TIME-OF-FLIGHT MASS-SPECTROMETRY OF NITRATED POLYCYCLIC AROMATIC-HYDROCARBONS

Nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) are widespread environmental pollutants that are generated by incomplete combustion a nd by atmospheric transformation of polycyclic aromatic hydrocarbons ( PAHs). Many nitro-PAH compounds are potent genotoxins and some are dir ect acting mutagens. Detection of nitro-PAHs in aerosols is-complicate d by small sample sizes and nitro-PAH abundances that are 1-2 orders o f magnitude less than analogous unsubstituted PAHs. Selective detectio n of several nitro-PAHs by using laser desorption ionization time-of-f light mass spectrometry in negative ion mode has been achieved. Desorp tion and ionization of nitro-PAHs were effected by using pulsed UV rad iation at 266 and 213 nm. Intense molecular anions were observed in ad dition to fragments identified as CN- and NO2-, which were characteris tic indicators of the presence of nitro-PAHs. Selective detection of n itro-PAHs in negative ion mode was demonstrated in the analysis of a d iesel particulate sample. (C) 1997 American Society for Mass Spectrome try.