Monday, December 5th, 2016

Meetings

NIH Proteomics Seminar

Date: December 8, 2016

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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 (Katherine.L.Fiedler@fda.hhs.gov) 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.

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October 2016 Meeting

Speaker: Douglas P. Ridge, Ph.D., University of Delaware

Topic: Fourier transform ion cyclotron resonance studies:  Examples including Infra-red multiphoton dissociation studies of cadmium sulfide metal clusters

Date: Monday, October 17, 2016

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

Location: Gerstel/Agilent Office, 701 Digital Drive #J, Linthicum Heights, MD 21090 (Directions)

Dinner: Please RSVP to Katherine Fiedler (Katherine.L.Fiedler@fda.hhs.gov) before October 17 if you will be attending the dinner.

Abstract: Fourier transform ion cyclotron resonance mass spectrometry involves injecting ions into an electromagnetic trap where they can be detected and mass analyzed on the basis of their cyclotron frequency.  The method facilitates manipulating the trapped ions in various informative ways.  The reactivity of trapped ions can be examined by exposing the trapped ions to reactive gases.  Structure and spectroscopic properties can be examined by subjecting the trapped ions to collisional or photon induced decomposition.  Examples of the applications of these techniques will be described.  In particular the application of these techniques to the study of Cadmium sulfide metal clusters will be described.  These metal clusters are important in marine environments both as potentially toxic pollutants and in relation to the exotic biology found around hydrothermal vents in the ocean floor.  Although cadmium sulfide is insoluble in water metal sulfide clusters can be prepared by electrospraying soluble metal salts such as cadmium acetate and allowing the resulting cadmium acetate clusters to react with H2S in the ion trap.  This results in clusters containing multiple Cd atoms and bisulfide and sulfide counter ions.  The structure of these clusters have been probed by subjecting them to collision induced decomposition, IR multiphoton dissociation, and density functional theory calculations.  Among the conclusions is that when excited the clusters tend to lose preferentially metal atoms forming a series of clusters containing hypervalent polysulfides.

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