Interpretation of mass spectra from organic compounds in aerosol time-of-flight mass spectrometry

Organic compounds containing a variety of functional groups have been analy zed using aerosol time-of-flight mass spectrometry, Both positive and negat ive laser desorption/ionization mass spectra have been acquired for compoun ds of relevance to ambient air particulate matter, including polycyclic aro matic hydrocarbons, heterocyclic analogues, aromatic oxygenated compounds s uch as phenols and acids, aliphatic dicarboxylic acids, and reduced nitroge n species such as amines. In many cases, positive ion mass spectra are simi lar to those found in libraries for 70-eV electron impact mass spectrometry . However, formation of even-electron molecular ions due to adduct formatio n also plays a major role in ion formation, Negative ion mass spectra sugge st that organic compounds largely disintegrate into carbon cluster fragment s (C-n(-) and CnH-). However, information about the heteroatoms present in organic molecules, especially nitrogen and oxygen, is carried dominantly by negative ion spectra, emphasizing the importance of simultaneous analysis of positive and negative ions in atmospheric samples.