Elemental, Micro, Ultra Trace Analysis

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Professor James Holcombe of the University of Texas Austin is supported by the Analytical and Surface Chemistry Program for research on microanalytical trace elemental analysis. Specifically, two areas are addressed: electrothermal vaporization (ETV) sample introduction into an inductively coupled mass spectrometer (ICPMS) and cold atom atomic absorption solution spectrometry (CAAASS). The idea is to develop analytical methods where the complexity of the matrix will not interfere with the analysis. ETV-ICPMS employs microsamples and places no sample introduction restrictions on the matrix, i.e., samples with high levels of dissolved salts, slurries and solids can all be used without dilution or digestion. Sample throughput rates, transport efficiencies and plasma loading (because of the complex matrix) are problems that are addressed. A low power, graphite-based filament system is being developed in lieu of the classical tube design or metal filament vaporizer. Insuring reproducible transport efficiency of the aerosol from the ETV to the ICP is the motivation behind the use of a microporous graphite tube and methodologies to center the aerosol in the gas flowing to the ICP. The thermal ramp of the ETV provides a crude chromatographic (thermal) separation device to inexpensively assist in discerning and circumventing interferences as well as optimizing the instantaneous signal to noise ratio. Although the proof-of-concept for ETV-ICP time-of-flight mass spectrometry has been demonstrated, this work focuses on the full implications and limitations of the method. Fundamental studies of aerosol dispersion as well as use of mixed gas plasma are also proposed. CAAASS is a novel means of generating atoms at room temperature in solution that was first demonstrated in Sturgeon's laboratory as a tool for sample introduction into an ICP. Holcombe's laboratory will investigate the fundamentals of these very interesting phenomena with the application goal of using the approach for elemental analysis via diode laser atomic absorption in a microchip. Elemental analysis remains a cornerstone in modern research and development. In the biological world, its use range from basic determination of cofactor concentrations to pharmokinetic evaluations of drugs (e.g. platinum in anticarcinogens). Because of their toxicity, many metals remain the focus of bioaccumulations. Water, soil and air analysis remains active since these are often the recirculating source of pollution and show impacts at exceedingly low levels. Basic geological sciences also rely on metals as tracers. While many viable approaches exist for basic ultratrace elemental detection, techniques for dealing with microsamples contained within a complex matrix consumes thousands of hours of effort to design methods, many of which are unique and useful only for the particular application. This research attempts to provide the broader research community with a tool that will most cost-effectively permit research to advance in a number of scientific and medical areas.