ATMOSPHERIC-PRESSURE CHEMICAL-IONIZATION OF ALKANES, ALKENES, AND CYCLOALKANES

Normal and cyclic alkanes and alkenes form stable gas-phase ions in air at atmospheric pressure from 40 to 200-degrees-C when moisture is below 1 ppm. Ionization of alkanes in a Ni-63 source favored charge transfer over proton transfer through pathways involving [M - 1]+ and [M - 3]+ ions. Ion mobility spectra for alkanes showed sharp and symmetrical profiles while spectra for alkenes suggested fragmentation. Ion identifications were made by using mass spectrometry, and ionization pathways were supported by using deuterated analogs of alkanes and alkenes. Alkanes were ionized seemingly through a hydrogen abstraction pathway and did not proceed through an alkene intermediate. New methods for interpretation of mobility spectra utilizing ion mobility spectrometry, atmospheric pressure chemical ionization mass spectrometry, chemical ionization mass spectrometry, and ion mobility spectrometry-mass spectrometry data were demonstrated.