title: Comparison of three plasma sources for ambient desorption/ionization mass spectrometry.
abstract: Plasma-based desorption/ionization sources are an important ionization technique for ambient surface analysis mass spectrometry. In this paper, we compare and contrast three competing plasma based desorption/ionization sources: a radio-frequency (rf) plasma needle, a dielectric barrier plasma jet, and a low-temperature plasma probe. The ambient composition of the three sources and their effectiveness at analyzing a range of pharmaceuticals and polymers were assessed. Results show that the background mass spectrum of each source was dominated by air species, with the rf needle producing a richer ion spectrum consisting mainly of ionized water clusters. It was also seen that each source produced different ion fragments of the analytes under investigation: this is thought to be due to different substrate heating, different ion transport mechanisms, and different electric field orientations. The rf needle was found to fragment the analytes least and as a result it was able to detect larger polymer ions than the other sources.
authors.affiliation: Department of Electrical Engineering and Electronics, University of Liverpool, Brownlow Hill, L69 3GJ, UK.
authors.forename: Kirsty
authors.initials: K
authors.lastname: McKay
authors.forename: Tara L
authors.initials: TL
authors.lastname: Salter
authors.forename: Andrew
authors.initials: A
authors.lastname: Bowfield
authors.forename: James L
authors.initials: JL
authors.lastname: Walsh
authors.forename: Ian S
authors.initials: IS
authors.lastname: Gilmore
authors.forename: James W
authors.initials: JW
authors.lastname: Bradley
mesh_terms: D004867:Equipment Design; D007477:Ions / Q000737:chemistry*; D058626:Plasma Gases / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000295:instrumentation*; D013696:Temperature
chemical_list: D007477:Ions; D058626:Plasma Gases