Identifying airborne carbonyl compounds in isoprene atmospheric photooxidation products by their PFBHA oximes using gas chromatography/ion trap mass spectrometry

Coupled with gas chromatographic/mass spectrometric detection, the oxime formation of aldehydes and ketones by reaction with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA) can be used to determine multi-functional airborne carbonyls as well as simple carbonyls. In this study, we report that methane chemical ionization of the PFBHA-carbonyl derivatives in an ion trap mass spectrometer provides for the determination of molecular weights of unknown carbonyls. We first report the study of model carbonyl compounds and then illustrate examples of detecting and identifying carbonyl products from methyl vinyl ketone and methacrolein experiments conducted in an indoor irradiation chamber and from isoprene experiments conducted in a dual outdoor smog chamber. The examples show th at multifunctional carbonyls do account for part of the missing reaction products in the atmospheric oxidation of isoprene. The advantages of PFBHA derivatives over the normally used 2,4-dinitrophenylhydrazine (DNPH) derivatives will also be discussed