Gas chromatographic enantiomer separation of agrochemicals using modified cyclodextrins

The enantiomers of phenoxypropionic acid type herbicides have been resolved by capillary gas chromatography employing modified cyclodextrins as chiral stationary phases. Excellent separations were obtained with columns containing a 1:1 mixture of per‐ O ‐pentylated and per‐ O ‐methylated γ‐cyclodextrin. The enantiomers of the methyl esters of mecoprop and dichlorprop were also resolved on octakis(3‐ O ‐butyryl‐2,6‐di‐ O ‐pentyl)‐γ‐cyclodextrin. On this phase the order of elution of the enantiomers was temperature‐dependent, the elution order being reversed as the temperature passed through the isoenantioselective temperature. This is the first time such behavior has been observed with cyclodextrin derivatives. The enantiomers of the polychlorinated polycyclic pesticides cis ‐ and trans ‐chlordane, oxychlordane, heptachlor, heptachlorepoxide, and three chiral organophosphorus pesticides could be resolved using selectively derivatized cyclodextrin derivatives.