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.
The combination of UV and diode-laser polarimetric detection of chiral molecules offers significant advantages in high performance liquid chromatography. The method described here circumvents the derivatization step and the use of chiral stationary or mobile phases for the resolution of enantiomers. Data acquisition of the polarimeter was performed with AC/DC interface and software Pic0 ADC-100 coupled to the polarimeter detector. Quantitative methods in the range 1-150 pg and 1-600 pg of (+)-cinchonine and (-)-cinchonidine, respectively, were established. Enantiomeric ratio determined by using UV and diode-laser polarimetric data without chiral separation is discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.