ENANTIOSELECTIVE DETERMINATION OF CHLORDANE COMPONENTS, METABOLITES, AND PHOTOCONVERSION PRODUCTS IN ENVIRONMENTAL-SAMPLES USING CHIRAL HIGH-RESOLUTION GAS-CHROMATOGRAPHY AND MASS-SPECTROMETRY

Enantiomer separation of various chlordane compounds, including heptachlor, the oxygenated metabolites heptachlor epoxide (HEP) and oxychlordane (OXY), and photoconversion products was investigated using chiral high-resolution gas chromatography and detection by electron ionization (EI) and electron-capture, negative ionization (ECNI) mass spectrometry (MS). In technical chlordane and in ambient air from Scandinavia, heptachlor and the chiral octa- and nonachlordanes were present in enantiomeric ratios of 1:1. The results indicate input of these compounds via aerial transport into the northern environment as racemic mixtures. Laboratory experiments using solid-phase photolysis by natural sunlight yielded caged and half-caged products from heptachlor and cis-chlordane, respectively. HEP was identified as a photooxidation product of heptachlor and formed in an enantiomeric ratio of 1:1. In contrast, incubation of heptachlor with rat liver homogenate (S9 fraction) yielded predominantly one enantiomer of HEP, likely due to the stereoselectivity of the mixed-function oxidase system. Biota from the Baltic (fish, seal), Arctic (seal), and Antarctic (penguin) showed changed isomeric and enantiomeric compositions of the octa- and nonachlordanes as compared to technical chlordane, and the metabolites HEP and OXY present in enantiomeric ratios differing from 1:1. The finding of photoheptachlor and photo-cis-chlordanes in these species document that photoreactions of chlordane compounds play a role in the transformation of these compounds in the environment.