DETERMINATION OF CHLOROPYRIDINE ISOMERS BY GAS-CHROMATOGRAPHY AND HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY IN CHLORPYRIFOS PROCESS-DEVELOPMENT

Vapour phase chlorination of pyridine yields pentachloropyridine, and selective reduction of pentachloropyridine gives 2,3,5,6-tetrachloropyridine, both being important industrial intermediates. Various other isomeric chloropyridines may be formed during the chlorination reaction, and gas and high-performance liquid chromatographic methods are described for the separation and determination of chloropyridine isomers obtained during the vapour phase chlorination of pyridine. The methods have been successfully tested on the process development of the insecticide chlorpyrifos.