November 2016 Meeting

Speaker: Kenyon M. Evans-Nguyen, The University of Tampa

Topic: Towards fieldable, combined atomic/molecular ion sources for mass spectrometry

Date: Monday, November 21, 2016

Time: 6:15 pm Dinner, 7:15 pm: Presentation

Location: Shimadzu Scientific Instrument, Inc. Training Center 7100 Riverwood Drive, Columbia, MD 21046 (Directions)

Dinner: Please RSVP to Katherine Fiedler ( before November 21 if you will be attending the dinner or are a presenting as a vendor.

Abstract:While the number of soft ambient ionization sources for molecular analysis has flourished, the development of ambient ionization sources for elemental analysis has been limited. The ruggedness and potential fieldability of microwave plasmas makes them appealing as potential ambient ionization sources. Indeed, microwave induced plasmas (MIPDI) have been used for ambient molecular ionization of organic compounds. The focus of this work is direct, simultaneous molecular and atomic characterization of solids using a microwave plasma for ambient ionization.

A relatively low temperature microwave plasma was achieved using a modification of previous designs for a microwave plasma torch. The plasma was coupled to a Thermo LTQ XL ion trap. A high argon flow was used to maintain high gas velocity at the tip of the plasma and facilitated direct ambient elemental ionization of solid substrates. There was no noticeable damage to most substrates and no significant heating. Molecular and atomic species were observed simultaneously for mixtures deposited on metal mesh substrates. For a mixture of the organic explosive RDX and uranium, both species were
observed in the spectra.

In recent work, the nozzle size in the plasma source tip has been restricted, resulting in a smaller microwave plasma with reduced gas and power requirements. Further, the microwave plasma source is being coupled with a compact 1064 nm q-switch laser
capable of 25 mJ pulses, with the intention of producing a portable laser ablation-plasma ionization source capable of both elemental and molecular analysis at surfaces.