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ENANTIOSELECTIVE DETERMINATION OF PESTICIDE RESIDUE IN AQUATIC ORGANISMS

This factor relates to the inherent chiral selectivity of living organisms. This is an important criterion, since a number of synthetic pesticides possess one or more stereogenic centers resulting in two or more enantiomers. Often only one of the enantiomers possesses the desired biochemical properties, while others may produce deleterious effects. The magnitude of the problem is unknown, and no regulations concerning the enantiomeric purity of pesticides are in place.

The present study monitors the enantioselectivity of pesticide residues in aquatic organisms and compares it to the non-selective accumulation in the abiotic samples. The initial experiments have been carried out with chlordane because it is the most prevalent chlorinated hydrocarbon contaminant in Missouri's natural water bodies. The major constituent of technical chlordane, the octachloro dicyclopentadiene, has four enantiomeric forms and is a good model compound for investigating enantioselectivity.

Enantiospecific monitoring was achieved with a two-dimensional gas chromatograph system. In this system, conventional (achiral) separations are carried out, then the peaks of interest are heart cut to a chiral selective column. The tandem system permitted unambiguous identification of chiral selective residues at sub parts per billion levels.

Key words: aquatic organisms, pesticide residues, enantioselectivity, chiral selective residues.