Advances in analytical spectrochemistry with ionized gases. I. Improved fundamental understanding through laser based techniques. II. Novel bioanalytical applications

Over the past several decades plasma spectrochemistry has become the workhorse for performing elemental analysis. Nevertheless, we are still far from fully understanding the fundamental mechanisms that affect and led to the production of the analytical signal. Thus, the first part of this study was focused on improving our knowledge of plasma fundamental processes. First, the effect of exposing an inductively coupled plasma to a mass spectrometer sampling interface was investigated. Our results show that the mass spectrometer sampler affects the plasma fundamental parameters in a way that changes with gas flow, forward r.f. power, and plasma torch-to-sampler distance. The findings help to better explain the plasma sampling process and have made clear that results from mass-spectrometry based plasma diagnostics are applicable to unperturbed plasmas only as a rough approximation. Second, and instrument was constructed to characterize the fundamental parameters of an analytical glow discharge by using Thomson and Rayleigh laser scattering. A continuous dc glow discharge source was studied and a set of corresponding numerical modeling experiments were performed. The resulting theory agrees qualitatively with the experimental findings; moreover, the theoretical and experimental techniques often provide complementary information. Finally, a temporally and spatially resolved map of the fundamental parameters of a dc glow discharge operated in pulsed mode was obtained. The results confirm previously proposed electron energy-transfer mechanisms at the beginning of the pulse. In contrast, the findings call into question other mechanisms involving plasma gas metastable formation proposed for the time period immediately after the end of the pulse.; In the second part of the study an imaging radio frequency glow discharge instrument was developed to provide three-dimensional elemental analysis of solids. The newly developed instrument was then applied to the simultaneous analysis of blotted biopolymers separated via gel electrophoresis.