Quantitative supercritical fluid extraction of organics.
Item
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Title
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Quantitative supercritical fluid extraction of organics.
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Identifier
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AAI9108145
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identifier
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9108145
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Creator
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Mahanama, Kariyawasam Ranaweerage Ranjith.
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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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Off-line supercritical fluid extraction developed specifically for analytical sample preparation and analysis of middle-sized PAHs are described. The analytical SCFE method has been evaluated with emphasis on the efficiency of the extraction and collection steps. Solid adsorbent traps (silica and octadecyl bonded phase) demonstrated the capability of collecting extracted compounds efficiently. Experimental parameters were evaluated to optimize the extraction of middle-sized PAHs and it was found that the efficiency of extraction increases with pressure (density) and temperature. Quantitative extractions were performed at 544 atm, 60{dollar}\sp\circ{dollar}C for 15 minutes. Enhancement of the efficiency of extraction is due to two factors: enhancement due to the greater molecular interactions with the increase of the pressure (density) and enhancement due to the vapor phase composition with the increase of temperature. Solubility of iso-ring PAHs in SCF vary with the size and molecular topology. Peri-condensed pyrene dissolves easily in SCF carbon dioxide compared to analog cata-annelated chrysene and triphenylene. This trend is similar to the variation of melting point with the molecular structure.;Extractions of spiked samples from sorptive Montour fly ash samples were quantitative except for benzo (a) pyrene and acenaphthalene. Extraction of spiked top soil samples demonstrated an easier extraction medium than sorptive fly ash. Nonpolar aliphatic hydrocarbons modifiers enhanced the recovery of PAHs from fly ash. It was found that the enhancement increases with the carbon number of the modifier but the selectivity of the extraction decreases rapidly. SCF extracts were cleaner than liquid extracts and selective HPLC-UVD determinations eliminated extra sample handling and tedious separation techniques.;As demonstrated by quantitative recovery of standard PAHs, SCF carbon dioxide provides a powerful alternative to liquid solvents for the extraction and recovery of PAHs. The extractions are simple, inexpensive and rapid to perform. Four to five extractions can easily be performed within two hours. Use of carbon dioxide as the SCF solvent made solvent disposal problems and toxicological problems of exposure to the solvent insignificant compared to conventional liquids. Extracted materials are not exposed to the light or to excessive heat which reduces the possibility of photo- or thermo-decompositions. Overall this is a much superior method for the extraction and analysis of middle-size PAHs.
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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.
