Browsing by Author "Motley, Curtis Bobby"

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    The evaluation of an argon and helium highly efficient microwave induced plasma as an element selective detector for packed column super critical fluid chromatography
    Motley, Curtis Bobby (Virginia Tech, 1990)
    Atomic emission spectroscopy is a powerful method for chemical analysis because it offers convenient qualitative and quantitative determination of the elemental composition of an analytical sample. Although most frequently used to determine the total concentration of a given analyte, atomic spectroscopy may be coupled with a separation technique to aid in the elemental identification of individual species. Recently, supercritical fluid chromatography (SFC) has gained popularity among the research community partially because SFC is much more tolerant of polar functional groups than is gas chromatorgraphy (GC). SFC can be used in applications where derivatization is not possible due to sample complexity or steric hindrance. However, these polar compounds often require the addition of polar organic solvents to SFC to improve retention characteristics and peak shape. These polar modifiers reduce or eliminate the utility of flame-based detectors. Therefore, researchers have begun to look for alternative detection systems for SFC with polar modifiers. In particular, atomic emission based detectors using plasmas have become popular to fill this void. This research stems from several characteristics that the plasma based detectors possess which make them more appealing than flame-based photometric detectors. These characteristics include improved analytical sensitivity, fewer spectral interferences, a wide dynamic range and the ability to tolerate polar organic modifiers. Possibly the most important attraction of the plasma detector is, with respect to chromatographic analyses, that this detector allows analysis of compounds that co-elute from a column because the detector is element-specific. The evaluation of the high efficiency microwave induced plasma (HEMIP) as an elemental selective detector for packed column supercritical fluid chromatography has been explored in this dissertation. The effect of CO₂ introduction on the analytical parameters of the plasma, the feasibility of coupling packed column supercritical fluid chromatography to the argon HEMIP for the determination of metals, the use of a helium sustained plasma for nonmetal determinations, and the application of the He-HEMIP as a sensitive and selective detector for packed-column SFC.
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    A Helium high efficiency microwave induced plasma for the atomic spectrometric determination of metals and nonmetals
    Perkins, Larry D.; Motley, Curtis Bobby; McCleary, Keith Alan; Long, Gary L. (Virginia Water Resources Research Center, Virginia Polytechnic Institute and State University, 1991)