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 laye r chromatography using water - methanol mixtures as eluents. The pesti cides showed regular retention behavior, their R(M) values decreasing linearly with increasing concentration of methanol in the eluent. Surp risingly, the lipophilicity and specific hydrophobic surface area of p esticides were highly intercorrelated, although the chemical structure s of the pesticides were extremely different. Principal component anal ysis proved that when both lipophilicity and specific hydrophobic surf ace area were taken into account simultaneously the herbicides, insect icides, 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 surfa ce area alone.