RELATIONSHIP BETWEEN LIPOPHILICITY AND SPECIFIC HYDROPHOBIC SURFACE-AREA OF A NONHOMOLOGOUS SERIES OF PESTICIDES

The lipophilicity and specific hydrophobic surface area of thirty one commercial pesticides have been determined by reversed phase thin layer chromatography using water - methanol mixtures as eluents. The pesticides showed regular retention behavior, their R(M) values decreasing linearly with increasing concentration of methanol in the eluent. Surprisingly, the lipophilicity and specific hydrophobic surface area of pesticides were highly intercorrelated, although the chemical structures of the pesticides were extremely different. Principal component analysis proved that when both lipophilicity and specific hydrophobic surface area were taken into account simultaneously the herbicides, insecticides, and fungicides could not be distinguished. This indicates that differences in the biological activity of these pesticides cannot be attributed to either their lipophilicity or specific hydrophobic surface area alone.