The Analysis of PPM Levels of Gases in Air By Photoionization Mass Spectrometry

Abstract

The body of information in this paper is directed toward individuals involved in the analysis of trace gases in air. The photoionization mass spectrometer has been investigated for a variety of potential inorganic and organic air pollutants at four ionizing wavelengths. The three aspects studied were (a) selective ionization of trace gases eliminating the ionization of the major components of air, (b) simplification of mass spectral fragmentation patterns, and (c) currently feasible sensitivities and detection limits. The results demonstrate that photoionization is superior to electron impact ionization for the first two aspects. The measured sensitivities and calculated detection limits require some improvement. It is shown that the necessary sensitivities can be obtained by eliminating the UV monochromator and using direct ionization with a hydrogen light source.