Development and applications of laser-enhanced ionization, laser-induced fluorescence, and photoionization detection systems for trace detection of elements and compounds of environmental and biological significance.

摘要

Many of the techniques currently used for the analysis of chemical species of biological and environmental significance suffer from problems that limit their use in complex sample matrices. Laser based detection systems (laser enhanced ionization (LEI), laser induced fluorescence (LIF), and photoionization spectrometry (PIS)) have been developed and applied to the determination of several elements in aqueous and solid media and nitric oxide and related compounds in the gas phase.; Laser enhanced ionization determinations of Cu, Sb, As, and Se have been carried out in a flame atomizer using far-ultraviolet transitions that have not been utilized previously. The limits of detection (LOD's) achieved for these elements by LEI in an argon/oxygen/acetylene flame are the best achieved for any analytical flame-based analysis technique for these elements. The elements As, Se, and Sb are all amenable to the hydride generation (HG) sample introduction technique. This technique has been combined with high sensitivity LIF detection in a flame atomizer, and the LOD's obtained are equal to or better than any other technique reported. This HG-LIF system has been applied to a feasibility study of the phytoremediation of As by poplar plants. In addition, the speciation of As and Se has been demonstrated using sequential analysis techniques, along with online separation of the species by ion chromatography (Se) or high performance liquid chromatography (As). Laser ablation sampling has been investigated for the analysis of As, Se, and Sb in thin films on microscope slides. The LOD's obtained in these investigations are the best ever reported using a direct analysis-laser ablation technique. Additionally, the Se content of prostate tissue slices has been investigated. LIF studies have been undertaken in a tungsten coil electrothermal atomizer, and the initial results from 12 elements studied indicate a high potential for such an analysis technique.; Nitric oxide (NO) and nitrogen dioxide (NO2) have been investigated using a LIF technique and a PIS technique, with the PIS technique demonstrating higher sensitivity. Unexpected enhancements were observed in the PIS spectra, and these enhancements have been attributed to resonance or near resonance ionization processes.