Atmospheric-pressure solution-cathode glow discharge: A versatile ion source for atomic and molecular mass spectrometry

Journal Article · Fri Nov 11 00:00:00 EST 2016 · Analytica Chimica Acta

DOI:https://doi.org/10.1016/j.aca.2016.10.045· OSTI ID:1421375

Schwartz, Andrew J. ^[1]; Williams, Kelsey L. ^[2]; Hieftje, Gary M. ^[1]; Shelley, Jacob T.  ^[3]

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1. Indiana University, Bloomington, IN (United States)
2. Kent State University, Kent, OH (United States)
3. Kent State University, Kent, OH (United States); Rensselaer Polytechnic Institute, Troy, NY (United States)

We report an atmospheric-pressure solution-cathode glow discharge (SCGD) has been evaluated as an ion source for atomic, molecular, and ambient desorption/ionization mass spectrometry. The SCGD consists of a direct-current plasma, supported in the ambient air in the absence of gas flows, and sustained upon the surface of a flowing liquid cathode. Analytes introduced in the flowing liquid, as an ambient gas, or as a solid held near the plasma are vaporized and ionized by interactions within or near the discharge. Introduction of acidic solutions containing metal salts produced bare elemental ions as well as H₂O, OH^- and NO₃^- adducts. Detection limits for these elemental species ranged from 0.1 to 4 ppb, working curves spanned more than 4 orders of linear dynamic range, and precision varied between 5 and 16% relative standard deviation. Small organic molecules were also efficiently ionized from solution, and both the intact molecular ion and fragments were observed in the resulting SCGD mass spectra. Fragmentation of molecular species was found to be tunable; high discharge currents led to harder ionization, while low discharge currents produced stronger molecular-ion signals. Ambient gases and solids, desorbed by the plasma from a glass probe, were also readily ionized by the SCGD. Indeed, strong analyte signals were obtained from solid samples placed at least 2 cm from the plasma. These findings indicate that the SCGD might be useful also for ambient desorption/ionization mass spectrometry. In conclusion, combined with earlier results that showed the SCGD is useful for ionization of labile biomolecules, the results here indicate that the SCGD is a highly versatile ion source capable of providing both elemental and molecular mass-spectral information.

• Research Organization: Indiana Univ., Bloomington, IN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division; Indiana University; USDOE
• Grant/Contract Number: FG02-98ER14890
• OSTI ID: 1421375
• Alternate ID(s): OSTI ID: 1396848
• Journal Information: Analytica Chimica Acta, Vol. 950, Issue C; ISSN 0003-2670
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
solution-cathode glow discharge
mass spectrometry
ionization source development
elemental analysis
ambient desorption/ionization
tunable fragmentation