Enantioselective Analysis of a Heptachlorobornane Isolated from the Technical Product Melipax by Gas Chromatography/Mass Spectrometry

Abstract

A heptachloro compound of technical toxaphene (CTT), recently isolated from the technical mixture Melipax, was enantioseparated by application of gas chromatography/mass spectrometry (GC/MS) with a chiral stationary phase. Using tert-butyldimethylsilylated β-cyclodextrin and two different ionization techniques, the first eluted enantiomer of 2-exo,3-endo,5-exo,9,9,10,10-heptachlorobornane (B7-1453) was found in significantly more abundance. Furthermore, the enantiomeric ratio (ER) of 1.26 ± 0.03 was reproduced after GC-ECD analysis on another chiral stationary phase, heptakis(6-O-tert-butyldimethylsilyl-2,3-di-O-methyl)-β-cyclodextrin. This confirms that B7-1453 was not present in racemic composition in the technical product. At present it is not clear if other technical products also contain B7-1453 and other compounds in nonracemic composition. Several synthesized CTT standards, however, showed racemic composition. An ER of 1.0 for B7-1453 was determined in a cod liver extract. Assuming that B7-1453 was present in nonracemic composition in the source of contamination, the ER of 1.0 in the cod liver would have been the result of a faster degradation of the first eluted enantiomer, which finally led to an ER of 1.0. If the source of contamination contained B7-1453 in racemic composition, the cod did not degrade B7-1453 enantioselectively. In this case, enantioselective analysis of CTTs in biota may be used to find the source of contamination. Keywords: Pesticide; toxaphene; gas chromatography; mass spectrometry; enantiomer separation