Resolution of deltamethrin, permethrin, and cypermethrin enantiomers by high-performance liquid chromatography with diode-laser polarimetric detection

A normal-phase liquid chromatographic method is used to resolve the stereoisomers of the pyrethroid insecticides deltamethrin, cypermethrin, and permethrin by using two detectors: an ultraviolet (UV) spectrometer and a diode-laser polarimeter. In a mixture of enantiomers and diastereomers such as those resulting from the chemical structure of the pyrethroid insecticides with several asymmetric carbons, the UV spectrometer allows the detection of the diastereomers, whereas the diode-laser polarimeter permits the identification of the enantiomers. In this work, two enantiomers of deltamethrin, all four enantiomers of permethrin, and the four diastereomeric forms of cypermethrin are resolved without physical separation.