Isomer-selective and enantiomerselective determination of DDT and related compounds using chiral high-resolution gas chromatography/mass spectrometry and chiral high-performance liquid chromatography

Article abstract of DOI:10.1021/ac00111a030

The composition of technical DDT was investigated using achiral and chiral high-resolution gas chromatography (HRGC) and electron-ionization mass spectrometry (EIMS). 2,4′-DDT and 2,4′-DDD, two important components of technical DDT, were enantiomerically resolved by chiral HRGC with silylated β-cyclodextrin and by chiral high-performance chromatography (HPLC) with permethylated γ-cyclodextrin as chiral selectors. The (+)- and (-)- enantiomers were assigned by chiral HPLC using chiroptical measurements. Enantiopure isolates were then used to identify these enantiomers in chiral HRGC analyses. Previous data indicated (+)- and (-)-2,4′-DDT to have S- and R-configuration, respectively, but the absolute configurations for (+)- and (-)-2,4′-DDD were hitherto unknown. They were now assigned via the reductive dechlorination of the individual 2,4′-DDT enantiomers which proceeded stereoselectively to the corresponding 2,4′-DDD enantiomers. The results showed (+)- and (-)-2,4′-DDD to have R- and S-configuration, respectively. The enantiomers of 2,4′-DDD thus have reversed signs of rotation for polarized light compared to the enantiomers of 2,4′-DDT with the same configuration. The enantiomer resolution of several additional chiral compounds in technical DDT is reported; enantiomeric ratios of ≈1.0 indicated all chiral compounds to be present as racemates in the technical and in the synthetic reference materials. We report the first enantioselective determinations of technical DDT; the methods presented should also be applicable to the analysis of environmental and biological samples.