The Effects of Added Hydrogen on Noble Gas Discharges Used as Ambient Desorption/Ionization Sources for Mass Spectrometry

Abstract

Abstract. We demonstrate the effectiveness of using hydrogen-doped argon as the support gas for the dielectric barrier discharge (DBD) ambient desorption/ionization (ADI) source in mass spectrometry. Also, we explore the chemistry responsible for the signal enhancement observed when using both hydrogen-doped argon and hydrogen-doped helium. The hydrogen-doped argon was tested for five analytes representing different classes of molecules. Addition of hydrogen to the argon plasma gas enhanced signals for gas-phase analytes and for analytes coated onto glass slides in positive and negative ion mode. The enhancements ranged from factors of 4 to 5 for gas-phase analytes and factors of 2 to 40 for coated slides. There was no significant increase in the background. The limit of detection for caffeine was lowered by a factor of 79 using H 2 /Ar and 2 using H 2 /He. Results are shown that help explain the fundamental differences between the pure-gas discharges and those that are hydrogen-doped for both argon and helium. Experiments with different discharge geometries and grounding schemes indicate that observed signal enhancements are strongly dependent on discharge configuration.

Precursors for Atmospheric Plasma‐Enhanced Sintering: Low‐Temperature Inkjet Printing of Conductive Copper

“…An atmospheric‐pressure dielectric barrier discharge (AP‐DBD) configuration operated at atmospheric pressure and supplied with an argon‐hydrogen mixture was selected, owing to its suitability for the treatment of large surfaces . A 97.5:2.5 argon–hydrogen plasma gas composition was selected to maximize the concentration of reactive hydrogen species that favor the low‐temperature reduction of MOD ink and promote a non‐thermal desorption of the ligands . In contrast to our previous work, where the plasma‐assisted inkjet printing of silver required numerous fast and short inkjet printing/plasma‐enhanced sintering cycles (ca.…”

Modern Plasma‐based Desorption/Ionization: From Atoms and Molecules to Chemical Synthesis

“…These ions have been observed with flowing afterglow MS (Adams, Bohme, & Ferguson, 1970) and β‐particle ionization of rare gas hydrogen mixtures (Aquilanti et al, 1965), so their presence in a mixed gas plasma and participation in ionization processes is reasonable. In a follow‐up study, a similar signal enhancement was observed when hydrogen was doped into the argon plasma gas of an RF discharge (Ellis et al, 2016). In this case, the proton‐transfer reagents could include H 2 + , ArH + , Ar 2 + , ArH 2 + , H 3 + , and H + .…”

Optical and mass-spectral characterization of mixed-gas flowing atmospheric-pressure afterglow sources

“…, or even high-energy photons [29,41]. Both HeH + and H 3 + , at m/z 5 and 3, respectively, are too low of mass to be detected by the MS instruments used here or by Farnsworth et al [29,40,41]. Meanwhile, the role and contribution of vacuum-ultraviolet photoionization with mixed-gas FAPA will be the focus of a future publication.…”

“…Schütz et al [39] presented a survey emission spectrum from an argon-propane DBDI source that, ultimately, was shown to produce similar analyte ions and analytical performance to a helium 5 DBD. Farnsworth et al [29,40,41] has used a combination of emission, fluorescence, and absorption spectroscopies to monitor changes in helium species, particularly helium metastable atoms (He m ), in helium and He:H 2 DBD source. We draw on these earlier works to better understand plasma processes occurring in the mixed-gas FAPA sources tested here.…”