Supercritical fluid extraction of N-nitrosamines.
Item
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Title
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Supercritical fluid extraction of N-nitrosamines.
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Identifier
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AAI9315508
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identifier
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9315508
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Creator
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Tewani, Suresh.
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Contributor
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Adviser: David C. Locke
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Date
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1993
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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, Biochemistry | Chemistry, Analytical
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Abstract
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A detailed review of N-nitrosamines is presented in the first chapter of this thesis. The detailed chemistry of N-nitrosamines including the mechanism of carcinogenicity, modes of formation, inhibition and destruction are discussed in detail. The occurrence and risk assessment of human exposure of these suspect cancer agents is described along with practical considerations for minimizing their effects. The methods of isolation and analysis of N-nitrosamines are critically discussed with special emphasis on Gas Chromatography (GC)-Electrochemical Detectors, GC-High Resolution Mass Spectrometry (GC-HRMS), GC-Thermal Energy Analyser (GC-TEA).;In the second chapter, the theoretical concepts of supercritical fluid extraction (SFE) are discussed in general. A comparison of physical and chemical properties of supercritical fluids (SF) with other phases is given. A comparison of static, dynamic, recirculating SFEs shows the versatility of this technique. The advantages over conventional methods such as Soxhlet extraction are also discussed. The instrumentation and operational technique of a laboratory built supercritical fluid extractor is explained. A brief review of applications (industrial and analytical) of SFE is given at the end of the second chapter.;The evaluation of SFE for analytical sample preparation and analyses of volatile N-nitrosamines (VNAs), tobacco specific N-nitrosamines (TSNAs), and N-nitrosodiethanolamine (NDELA) from spiked matrices, tobacco and cutting fluids is presented in the third chapter. Experimental parameters such as pressure, temperature, equilibration time, collector materials, modifier are evaluated to optimize the recoveries. The extracts are analysed by GC-TEA which is already proven to be highly selective and sensitive to quantitation of N-nitrosamines. The extraction of VNAs in pure SF-CO{dollar}\sb2{dollar} is quantitative at moderate pressures and low temperatures. However, for the extraction of TSNAs and NDELA, it is imperative to have high pressures and presence of an additive ({dollar}\sim{dollar}10% methanol) to achieve satisfactory results.;Overall, this study offers a simple, rapid, accurate and environmentally advantageous sample preparation technique for the estimation of N-nitrosamines at nanogram levels as an interim alternative to existing analytical methodology which offers only complex, time-consuming procedures.
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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.
