Analytical evaluation and applications of a radio-frequency glow discharge source for atomic emission spectrometry.

摘要

The glow discharge (GD) source has found its place in the analytical community within the last decade as a means of analyzing samples directly in the solid state. In the area of optical spectroscopy, the glow discharge has become competitive in a field once dominated by direct current (dc) arc and alternating current (ac) spark emission devices. Rapid changes in technology have placed extremely difficult demands on modern analytical techniques for the characterization of novel materials that are not directly amenable to traditional emission spectroscopic techniques. The development of radio-frequency powered glow discharge (rf-GD) devices, with their ability to sputter-atomize and excite both conductive and insulating materials, has therefore attracted much interest within the analytical community.; This work continues the development of rf-GD atomic emission spectrometry, utilizing the results from previous studies of characterization and optimization to expand the realm of analytical applications. In order to compare an emerging rf-GD methodology with the more traditional direct solids techniques, an evaluation of figures-of-merit was made including such pertinent characteristics as source stability, internal and sample-to-sample precision, accuracy and sensitivity.; Before evaluating figures-of-merit, essential criteria were established for selecting the optimal set of elemental transitions. In this work, a line selection methodology was devised in order to simplify both single and multi-component elemental analyses, while also being used to evaluate characteristic figures-of-merit. Once developed, this line selection process was used in trace element determinations of high-purity copper, aluminum, and precious metal matrices.; After establishing a line selection methodology that could be used for analytes at various concentrations in many different types of samples, further optimization continued for the purpose of obtaining the most realistic figures-of-merit for the rf-GD source. This involved the acquisition of noise power spectra in order to identify and subsequently eliminate, if necessary, any types of noise associated with the rf-GD source or the analytical system.; While establishing a comparison of rf-GD with the majority of other direct solids techniques, it was necessary to use samples restricted to the capabilities of the latter, i.e. solid conductive materials. In terms of glow discharge devices, dc powered sources provide a viable means of analysis for conductive solid samples directly. As the GD field expands to include more diverse sample types through the use of rf powered devices, it is important not to neglect the fundamental processes of each type of GD plasma. A comparison of emission spectral features and figures-of-merit was made between rf and dc powering for a GD source in order to understand fundamental and experimental differences. A Langmuir probe was also used to collect information on the electrical characteristics of the respective plasmas.; The diversity of materials that may be analyzed with rf-GD allows great versatility for the analytical chemist. This is especially important for samples that pose substantial difficulty for dissolution, and/or could pose a health threat to the analyst. A study was undertaken in order to determine the feasibility of rf-GD-AES to safely and effectively analyze radioactive vitrified waste, by conducting preliminary elemental analyses of simulated waste glasses from the Savannah River Site in Aiken, SC.; These studies were vital for the development of GD spectrometry, having provided further evidence that the rf-GD emission source is a viable tool for direct solids analysis of both conductive and nonconductive materials.