Date of Graduation
During the past decade, true chemical speciation has become increasingly important for environmental, clinical and nutritional chemists. Chemical speciation, by definition, is the identification of elements and their chemical environment in a given sample. The current and most popular trend for chemical speciation is to utilize hyphenated techniques, thus yielding two-dimensional information. Often, chromatography or an alternate separation technique is used to separate the mixture into its constituent components. Then, each component is interrogated by some spectroscopic technique. In nearly all cases, the nature of the compounds are inferred from their relative chromatographic properties, and the identification of elements and their relative concentrations are measured via spectroscopic techniques. While this approach provides a significant amount of information on a given sample, it is not speciation in a true chemical sense. Using micro- and milli-second pulsed glow discharge time of flight mass spectrometry and temporal gating techniques, elemental, structural and molecular information was obtained, concurrently from the same instrument. Samples were introduced into the pulsed plasma and allowed to interact with the plasma. Depending on the extent of these interactions, which is controllable at the discretion of the user, the samples may undergo soft chemical ionization yielding molecular ions or may be completely atomized and ionized yielding elemental information. The operator could chose the above interaction zones or anything in-between, which provides structural information through an electron ionization type fragmentation pattern. Detection of plasma produced ions was done by a time-of-flight mass spectrometer (ToF-MS) which is most suitable for complete mass spectrometric analysis of time gated transient events.
Moser, Matthew Alan, "Micro- and pulsed -plasmas: Fine tuning plasma energies for chemical analysis." (2002). Graduate Theses, Dissertations, and Problem Reports. 9458.