Fragmentation of organic compounds using low-pressure microwave-induced plasma mass spectrometry

Abstract

A low-pressure helium microwave-induced plasma (MIP) mass spectrometric system was used to obtain molecular fragmentation of organic compounds. Several alkanes and aromatic compounds of mass less than 160 were examined. The MIP was operated at a power of 20 W and a helium flow-rate of 26 ml min^–1. Analyte was introduced into the plasma within the expansion stage of a VG PlasmaQuad to obtain the desired fragmentation. The resulting fragmentation patterns were comparable to conventional electron impact spectra although the relative intensities were different. The effect of power, flow-rate and method of sample introduction on the production of ion fragments was examined. Increasing power produced less intense spectra and changes in the fragmentation patterns, eventually eliminating the molecular parent ion. The potential for using the same experimental set-up for obtaining structural information and quantitative elemental data was demonstrated. In addition, the potential of using nitrogen as the plasma gas to obtain fragmentation was examined.