Title

Ultra-violet and resonant laser ablation coupled with microwave-induced plasma atomic emission spectrometry and determination of tin in nickel-based alloys by electrothermal atomizer atomic absorption and laser-excited atomic fluorescence spectrometry

Date of Completion

January 1998

Keywords

Chemistry, Analytical|Engineering, Materials Science

Degree

Ph.D.

Abstract

Chapter 1 reviews laser ablation in analytical atomic spectrometry. Laser ablation is categorized into two functions: one is used as a sample introduction method, the other function is used as a microprobe analysis method. Both fundamental and applicational aspects are reviewed with the citations of related papers. This chapter also serves as an introduction to the work which is described in chapter 2 and chapter 3 as laser ablation is a relatively new research area for the research group.^ In chapter 2, instrumentation for excimer (308nm) laser ablation of samples was coupled with a microwave induced plasma (MLP), and evaluated for its potential as an approach to solid sampling for atomic emission spectrometry. Operating parameters were optimized, and the effects of laser repetition rate and number of laser shots on the emission signal were investigated. The UV excimer laser removed more material than would be expected of an infrared laser of similar energy. The chromium detection limit in the solid steel sample was estimated to be about 500 $\mu$g/g.^ In chapter 3, a wavelength tunable optical parametric oscillator (OPO) laser was used to ablate a steel sample into the same apparatus described in chapter 2. The emission signal for the elements was selectively enhanced when the ablation wavelength was tuned to be in resonance with any atomic transition of that element. This was the first report of the observation of resonant ablation by use of optical detection, as prior reports of resonant ablation have used mass spectrometric detectors.^ Chapter 4 reviews the publications in laser excited atomic fluorescence spectrometry in recent eight years. The focus of the review is on recent development on new instruments and applications of this technique.^ Chapter 5 studies the determination of tin in nickel-based alloys with laser excited atomic fluorescence in a graphite furnace. Zeeman electrothermal atomizer atomic absorption spectrometry and inductively coupled plasma mass spectrometry methods were also used. The laser excited atomic fluorescence method turned out to be as accurate as the other techniques. The atomic fluorescence method was simple to develop and did not need a sophisticated background correction technique to do the analyses. ^

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