STUDIES ON THE DETERMINATION AND METABOLISM OF TOXIC AROMATIC AMINES
Abstract
Aromatic amines comprise a diverse, commercially important and environmentally pervasive class of chemical products. Formerly very important intermediates in the synthetic dye industry and elsewhere, many are proven human carcinogens. A further assessment of the potential impact of these compounds requires the development of sensitive and specific instrumental analytical methodology for the routine determination of these analytes and their environmental and metabolic transformation products in small amounts of very complex samples. This Dissertation describes the development and evaluation of several innovative techniques based upon liquid chromatography/electrochemistry for these purposes. Following a description of the electrochemical and chromatographic characteristics of several common, representative amines, the performance characteristics of conventional methodology employing the solvent extraction prior to chromatographic quantitation are determined for benzidine and its acetylated metabolites added to human urine. A considerable improvement is demonstrated by utilizing precolumn sample preconcentration for the determination of five federally-regulated industrial products in several environmentally-derived samples. For benzidine added to river water, this procedure utilizes 20 mL of filtered sample, is linear from 25 pg/mL - 5 ng/mL, and the limit of detection is 5 pg/mL. Following a description of some of the major factors that appear to be important in the carcinogenic process, evidence is presented to support the suggestion that the metabolism of acetaminophen is a suitable model to describe the activation of benzidine to one possible carcinogenic metabolite, 4,4'-biphenoquinonediimine (BPQDI). By analogy with the known thioether conjugates of acetaminophen, it is shown that an identical sequence of thioether reaction products arises from the reaction of chemically-produced BPQDI with glutathione at physiological pH, and also when benzidine is incubated with a model enzyme system under identical conditions. Finally, precolumn sample extraction and subsequent column switching, in conjunction with chromatographically-assisted hydrodynamic voltammetry, is utilized to develop a model approach for the evaluation of this proposed minor metabolic pathway and for the tentative identification of several metabolites of benzidine in a representative whole animal model. The flexible analytical methodology employed in all of these studies is believed to be ideally suited for similar studies of many other toxic molecules of industrial, environmental, and medical importance.
Degree
Ph.D.
Subject Area
Analytical chemistry
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