A Distribution Chromatography Method for the Identification of Pesticides in Their Mixtures and Agricultural Products

Resumo

The distribution of 166 pesticides of various classes (amides, dinitroanilines, pyrethroids, thiocarbamates, triazines, etc.) was studied at 20 ± 1°C in multiple extraction systems. The distribution constants (P) of pesticides between hexane and a polar phase are calculated. Based on the distribution constants of pesticides, a possibility of using distribution chromatography for their identification was considered. It is demonstrated on an example of pesticides with similar retention times that the hexane–water extraction system is most selective and universal for the identification of most compounds by gas and liquid chromatography. Using this system, logarithms of distribution constants of the substances under consideration are maximally differentiated and ranged from–1.32 to 8.0. Such a range makes it possible, with an acceptable volume ratio of the hexane and water phases (up to 1: 500), to achieve a significant decrease in the peak area of the pesticide in hexane when it is washed with water in accordance with its P value up to logP = 3.0. In the case of more hydrophobic pesticides, extraction systems of hexane–ethylene glycol, hexane–acetonitrile, and hexane–mixtures of acetonitrile with water and ethylene glycol can be used.