El- and NCl-mass spectrometry of arylalkyl nitrates and their occurrence in urban air

The overall probability of the formation of arylalkyl nitrates is low in co mparison to alkyl nitrates. However, measurable amounts of arylalkyl nitrat es are found in traffic influenced air. It is reported here an analytical p rotocol based on high-volume sampling, adsorption liquid chromatography as a step in sample preparation, and high-resolution gas chromatography with e lectron ionization mass selective detection (HRGC/EI-MSD) as well as high-r esolution gas chromatography with negative chemical ionization mass selecti ve detection (HRGC/NCI (methane)-MSD) for the determination of arylalkyl ni trates as atmospheric constituents in urban air. The synthesis of arylalkyl nitrates as reference compounds is described. The arylalkyl nitrates can b e selectively detected by the fragments M-46 (M-NO2) and M-48 (M-NO2-2H) in HRGC/NCI(methane)-MSD. In EI(70 EV)-MSD the dominating ions are at 46, 77, 91 and 105 u, which correspond to the NO2+ and the phenyl, benzyl, and eth ylbenzene fragments, respectively. The molecular ions are missing in (NCI-m ethane)-MSD and are of medium intensity in EI-MSD. Phenylethyl and phenylpr opyl nitrates elute in GC in the range of n-octyl to n-dodecyl nitrate. The following arylalkyl nitrates have been identified in urban air: Benzyl nit rate (PhCl) and the three xylyl nitrates (M-PhCl), phenylethyl-l-nitrate (1 Ph1C2), phenylethyl-2-nitrate (1Ph2C2), phenyl-n-propyl-1-nitrate (1Ph1C3), and phenyl-n-propyl-2-nitrate (1Ph2C3). Benzyl nitrate is the dominating c ompound in this group and is found at levels of 10-300 ng/m(3) in urban air .