Temporal changes in purity and specific activity of tritium-labeled 2,3,7,8-tetrachlorodibenzo-p-dioxin: Radiopurity model for toxicology
The specific activity (S) and radiopurity (R) of tritium labeled 2,3,7,8-tetrachlorodibenzo-p-dioxin, [{sub 3}H]TCDD, were measured by gas chromatography/mass spectrometry (GC/MS) while attempting to accurately characterized TCDD doses received by invertebrates, fish, and fish embryos during several toxicology studies conducted over a 3 year period. The [{sub 3}H]TCDD sample was found to consist of six TCDD analogues involving hydrogen, deuterium, and tritium substitution at the 1,6-dibenzo-p-dioxin carbon positions and a complex mixture of impurities (with and without tritium labels). Planar aromatic impurities were identified a tolyl-TCDD adducts and appeared to result from the decay of {sub 3}H radiolabels to produce TCDD carbocations which reacted with the solvent, toluene. Formation of TriCDD and tolyl-TriCDDs, from both TCDD and tolyl-TCDDs, probably resulted from radiolysis-induced loss of a chlorine to form TriCDD free radicals which reacted with toluene. The measurement of S for [{sub 3}H]TCDD by GC/MS was accurate and precise ({+-}3%) because relative, rather than absolute, amounts of the analogues were determined. Changes in S over time were accurately modeled as a function of the conversion of each [{sub 3}H]TCDD analogue to a solvent-TCDD analogue at a rate determined by {sub 3}H loss due to decay. Storage, purification, and use of tritiated chemicals for toxicology studies requires consideration of the {sub 3}H decay-related phenomena. For example, hydroxylated TCDD is an expected decay reaction product of [{sub 3}H]TCDD in tissues and may be misidentified as a metabolite.
- Research Organization:
- Environmental Protection Agency, Duluth, MN (US)
- OSTI ID:
- 20000730
- Journal Information:
- Environmental Science and Technology, Vol. 33, Issue 20; Other Information: PBD: 15 Oct 1999; ISSN 0013-936X
- Country of Publication:
- United States
- Language:
- English
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