ANALYSIS OF AIRBORNE CARBOXYLIC-ACIDS AND PHENOLS AS THEIR PENTAFLUOROBENZYL DERIVATIVES - GAS-CHROMATOGRAPHY ION-TRAP MASS-SPECTROMETRY WITH A NOVEL CHEMICAL-IONIZATION REAGENT, PFBOH

The complex photochemical transformations of biogenic hydrocarbons suc h as isoprene and of anthropogenic hydrocarbons such as aromatics are an important source of carboxylic acids in the troposphere. The identi fication of unknown carboxylic acids can be difficult, however, due to the lack of standards as well as poor sensitivity and lack of selecti vity of existing techniques. In this study, we describe the developmen t of a method to analyze airborne carboxylic acids using derivatizatio n with pentafluorobenzyl bromide (PFBBr) followed by capillary gas chr omatography/ion trap mass spectrometry (GC/ITMS) analysis. In addition to the typical electron impact ionization (El) and methane chemical i onization (CI) mass spectra of pentafluorobenzyl derivatives, we descr ibe the use of pentafluorobenzyl alcohol (PFBOH) as a novel reagent ga s for CIMS. Pentafluorobenzyl ions (m/z = 181) were produced at reduce d pressure (1 x 10(-5)-2 x 10(-5) Torr) from PFBOH gas, and the result ing CIMS were characterized by the predominance of the [M + 181](+) io ns. The carboxylic acid products in the oxidation of isoprene from ind oor and outdoor smog chamber experiments were analyzed using the descr ibed PFBBr GC/ITMS method. The formation of methacrylic acid in an iso prene/O-3 reaction was demonstrated experimentally for the first time, and acrylic acid, one of the U.S. EPA 189 Hazardous Air Pollutants, i s first reported here as an isoprene oxidation product. In other outdo or toluene/NOx chamber experiments, we detected a series of carboxylic acids and various phenolic compounds using this method.