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Miniature Flow-Through Low-Temperature Plasma Ionization Source for Ambient Ionization of Gases and Aerosols

Spencer Sandra E., Santiago Brandon G., Glish Gary L.
Analytical chemistry 2015 v.87 no.23 pp. 11887-11892
aerosols, caffeine, cellulose, gases, ionization, ions, pyrolysis
The design and operation of an inexpensive, miniature low-temperature plasma ion source is detailed. The miniature low-temperature plasma ion source is operated in a “flow-through” configuration, wherein the gaseous or aerosolized analyte, caffeine or pyrolyzed ethyl cellulose, in a carrier gas is used as the plasma gas. In this flow-through configuration, the sensitivity for the caffeine standard and the pyrolysis products of ethyl cellulose is maintained or increased and the reproducibility of the ion source is increased. Changes in the relative intensity of ions from the aerosol produced by pyrolysis of ethyl cellulose are observed in the mass spectrum when the low-temperature plasma ion source is used in the flow-through configuration. Experiments suggest this change in relative intensity is likely due to differences in ionization efficiency rather than increased fragmentation of ethyl cellulose pyrolysis products during ionization. Flow-through low-temperature plasma ionization with the miniature ion source is shown to be a promising technique for the ionization of compounds in gases or aerosol particles.