Browsing by Author "Perkins, Larry D."
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- Development and characterization of a low power helium microwave induced plasma for spectrometric determinations of metals and nonmetalsPerkins, Larry D. (Virginia Polytechnic Institute and State University, 1989)This dissertation centers on the development of a new helium microwave induced plasma. The analytical utility of this new plasma source is critically evaluated. To sustain the helium plasma a TM ₀₁₀ high efficiency microwave induced plasma, HEMIP, was used. The HEMIP is a modification of the original Beenakker cavity that precludes the use of external matching devices, such as the highly popular double tuning stub. The He-HEMIP was analytically characterized as an atomization source for metals and nonmetals with the use of atomic emission spectrometry (AES) and atomic fluorescence spectrometry (AFS). A torodial plasma was sustained in the cavity solely by the helium gas output of the nebulizer. Aqueous samples from a pneumatic glass nebulizer/Scott spray chamber were aspirated into the cavity without a desolvation apparatus. With AES, detection limits for metals and nonmetals were in the sub-ppm range. with AFS, detection limits for metals were determined to be in the low ppm to sub-ppb range and were found to be not statistically different from those reported for HCL-ICP-AFS. Linear ranges for AES and AFS ranged from four up to five and one-half orders of concentrative magnitude. The effect of sample uptake rate on the emission intensity was investigated. Ionization interferences were determined to be minimal and phosphate interferences were found not to occur. Development and characterization also included studies of the He-HEMIP's physical characteristics. Excitation and ionization temperatures were found to be approximately equal, suggesting that the He—HEMIP approaches local thermodynamic equilibrium. Evaluation of the He—HEMIP as a routine detector for sulfur during coal pyrolysis and coal extracted samples was investigated. Results showed that the He-HEMIP is selective and sensitive. Detection values compared favorably to those of certified coal samples.
- The evaluation of a low powered microwave induced plasma as an atom cell for atomic spectrometryPerkins, Larry D. (Virginia Tech, 1987-05-15)The range of plasma spectroscopy tends to increase with the introduction of more efficient plasma excitation sources. In this thesis the use of one such plasma excitation source, the microwave induced plasma is evaluated as an atom cell for atomic spectrometry. The modes of spectrometry evaluated are atomic emission and atomic fluoresence. Analytical merits of the microwave induced plasma using detection limits and studies of interelement effects (i.e. vaporization, ionizationâ and scatter interferences) are also presented.
- A Helium high efficiency microwave induced plasma for the atomic spectrometric determination of metals and nonmetalsPerkins, Larry D.; Motley, Curtis Bobby; McCleary, Keith Alan; Long, Gary L. (Virginia Water Resources Research Center, Virginia Polytechnic Institute and State University, 1991)