Characterization and Optimization of Atomic Spectrometric Processes and Techniques

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With support from the Analytical and Surface Chemistry Program Dr. Gary M. Hieftje will continue studies intended to enhance the sensitivity, precision, accuracy and degree of utility of atomic spectrometric analysis. In one group of investigations, specially developed techniques will be employed to eluciate the mechanism of solute particle vaporization and atom formation in flames and plasmas of the kind used for multielement analysis. Clarification of these events is expected to reduce interelement interferences caused by incomplete vaporization. In a second area of investigation, rare-gas plasmas will be studied in an effort to determine how they are responsible for excitation of atoms and ions. Particular emphasis will be placed on understanding the characteristics of electrons in such discharges and the role electrons play in transferring plasma energy to analyte atoms and ions. In the third area, the sources of interferences in plasma source-mass spectrometry will be investigated. A typical plasma source, the mass spectrometer itself, and the interface that separates these will be examined in an effort to understand how the mass spectrometric sampling process influences a plasma, how the atmospheric-pressure gases are extracted through a medium-pressure interface into the mass spectrometer, and how space-charge effects in the mass spectrometer can influence accuracy, precision, and dynamic range in the resulting measurement. Finally, the factors that limit the utility of the glow-discharge lamp as a source will be explored, with special attention to the nature and rate of rare-gas sputtering in such sources. Atomic spectroscopy is a highly sensitive and convenient method for the identification and quantitative measurement of metals in biological and environmental samples. The results of this project are expected to contribute to substantial improvements in the utility and accuracy of this method.