Determination of [3H]-2,3,7,8-tetrachlorodibenzo-p-dioxin in human feces to ascertain its relative metabolism in man

Human feces samples from a self-dosing experiment were analyzed by gas chromatography/mass spectrometry (GC/MS) for [3H]-2,3,7,8-tetrachlorodibenzo-p-dioxin (3H-2378-TCDD) to determine that 36-44% of the radioactivity was attributable to the parent compound. This method, using isotope dilution analysis, proved to be difficult due to the unexpectedly higher native 2378-TCDD background which created abnormally large precision ranges around the calculated feces concentrations of 0.1-0.2 pg/g. These results were supported by additional analyses involving the GC/MS chemical cleanup method combined with liquid scintillation counting which showed that at most, 50% of the radioactivity was due to 2378-TCDD metabolites resulting in a minimum metabolism of 50% for these samples.