Structural elucidation of monoterpene oxidation products by ion trap fragmentation using on-line atmospheric pressure chemical ionisation mass spectrometry in the negative ion mode

Based on ion trap mass spectrometry, an on-line method is described which p rovides valuable information on the molecular composition of structurally c omplex organic aerosols. The investigated aerosols were generated from the gas-phase ozonolysis of various C10H16-terpenes (alpha -pinene, beta -pinen e, 3-carene, sabinene, limonene), and directly introduced into the ion sour ce of the mass spectrometer. Negative ion chemical ionisation at atmospheri c pressure (APCI(-)) enabled the detection of multifunctional carboxylic ac id products by combining inherent sensitivity and molecular weight informat ion. Sequential low-energy collision-induced product ion fragmentation expe riments (MSn) were performed in order to elucidate characteristic decomposi tion pathways of the compounds. Dicarboxylic acids, oxocarboxylic acids and hydroxyketocarboxylic acid products could be clearly distinguished by mult istage on-line MS. Furthermore, sabinonic acid and two C-9-ether compounds were tentatively identified for the first time by applying on-line APCI(-)- MSn. Copyright (C) 2001 John Wiley & Sons, Ltd.