Carbon isotope effects of DDTs in carrot during the digestion process using an in vitro test

Compound-specific carbon isotope ratio analysis is a promising tool to assess the origins and fates of organic contaminants in many fields. The present study aims to investigate the isotope effects of dichloro-diphenyl-trichloroethane (DDT) and its degradates in carrots during digestion processes simulating the human gastrointestinal tract. To accurately interpret isotopic data obtained for unreleased DDTs (p,p-DDT, p,p-DDD and p,p-DDE) from carrots during digestion, spiked carrots with known delta(13)C values of DDTs were incubated in simulated gastric and intestinal solutions using a static in vitro model of the human gut. The delta(13)C values and concentrations of DDTs remaining in the carrot and in the digestive solutions were measured. The difference in the delta(13)C values of the added DDTs and the matrix-bound DDTs after digestion was always <0.50 per thousand, which is within the technical specification of the analytical system, although the released DDTs increased or decreased under the digestion conditions. The study demonstrated that there were no significant carbon isotopic fractionations during digestion. To our knowledge, this is the first report demonstrating the isotope effect of organic compounds during stomach and small intestine digestion, and the first reported isotope analyses of DDTs.