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MASS SPECTROMETRY FOR DETERMINATION OF TETRACHLORODIBENZODIOXIN IN TISSUE AND FOR STUDIES OF THE STRUCTURE AND REACTIVITY OF ORGANIC IONS
Abstract
Section 1. High resolution gas chromatography/mass spectrometry (GC/MS) was used to quantitate 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in adipose tissue from Vietnam veterans. Interlaboratory validation using isomer specific capillary GC/MS confirmed reported detections. Observed levels correlated with the extent of exposure. The half-life of 2,3,7,8-TCDD in a rhesus macaque was determined by GC/MS analysis of adipose tissue after administration of a single oral dose (1 ug/kg) to be about one year. Analysis of feces and urine showed most of the TCDD (about 80%) excreted unmetabolized in feces. Section 2. A Frontier Molecular Orbital (FMO) approach to gas-phase radical-ion/molecule cycloadditions is presented. Parameters such as orbital energies, charge distribution, and FMO symmetry are utilized to make predictions which correlate with the observed reaction pathways. Regioselectivity of addition, and the use of Woodward Hoffman rules for radical-ion/molecule cycloadditions are considered. Section 3. The structure of C(,3)H(,5)('+) ions formed by radical halide loss from ionized allyl, cyclopropyl, 1-, and 2-propenyl halides was investigated by derivatizing them with neutral benzene and substituted benzenes to produce gas-phase adduct ions. The structures of the adducts were determined by collisional activation and comparison with the CID spectra of model ions. Two stable ion structures were observed, the allyl and 2-propenyl cations. The mechanism of adduct formation was also investigated, using Fourier transform mass spectrometry (FTMS) and pulsed ion cyclotron resonance (ICR) spectrometry. Rate constants for the reaction with benzene were dependent on the C(,3)H(,5)('+) ion structures. Section 4. The structures of C(,9)H(,10)('+) ions with 10('-11) to 10('-6) sec. lifetimes were investigated by field ionization (FI), collision induced dissociation (CID), and charge stripping techniques. The extent of ion isomerization was shown to be dependent on ion lifetime, and incomplete even at 10('-6) sec.
Subject Area
Analytical chemistry
Recommended Citation
LAY, JACKSON OLIVER, "MASS SPECTROMETRY FOR DETERMINATION OF TETRACHLORODIBENZODIOXIN IN TISSUE AND FOR STUDIES OF THE STRUCTURE AND REACTIVITY OF ORGANIC IONS" (1983). ETD collection for University of Nebraska-Lincoln. AAI8318665.
https://digitalcommons.unl.edu/dissertations/AAI8318665