Quantitative supercritical fluid extractions at trace levels.
Item
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Title
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Quantitative supercritical fluid extractions at trace levels.
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Identifier
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AAI9108173
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identifier
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9108173
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Creator
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Sharma, Avadhesh Kumar.
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Contributor
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Adviser: David C. Locke
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Date
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1990
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Analytical
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Abstract
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The technique of supercritical fluid extraction (SCFE) on the analytical scale is explored for the trace level isolation of various organic analytes from tenacious matrices. SCFE yields a clean, rapid, quantitative extract of the analyte which requires no further clean-up prior to analytical determination. Samples weighing a few grams are extracted in a closed system for a period of 15-20 minutes at pressures between 4000 and 8000 psi CO{dollar}\sb2{dollar} and in the temperature range 45-65{dollar}\sp\circ{dollar}C. To isolate the analyte, the extract-laden CO{dollar}\sb2{dollar} is depressurized across a short stainless steel tube packed with adsorbent such as silica, C-18, or Celite. The deposited material is eluted with a small volume of organic liquid and analyzed by HPLC, GC, or GC/MS.;The specific methods have been developed for quantitative supercritical fluid extractions to isolate trace levels of anthraquinone from wood and paper pulp, menadione from animal feed, vitamin K-1 from infant food formulas, vitamin A from ready-to-eat breakfast cereals, extraction of 1-nitropyrene from diesel exhaust samples, synthetic mixture of oxy-PAHs from carbon black, nitrosoamines from various cured foods, parathion from oil seeds and grains, and Diazepam from commercial formulations.;The use of highly selective electrochemical detector (ECD) for the HPLC enables direct analysis of extracts with no further clean-up, in the case of vitamin K-1, menadione, vitamin A, parathion, and nitrosoamines, which are extracted along with number of other, non-electoactive substances from lipid rich matrices. The ECD operated in the reductive mode with a silver working electrode offers high sensitivities (ca. 100 pg) and wide linear dynamic ranges (ca. 10{dollar}\sp4{dollar}) for the analytes investigated.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
