Reversed-phase high-performance liquid chromatography in quantitative structure–activity relationship studies of new fungicides

Abstract

The retention behaviour of 2,4-dihydroxythiobenzanilides in a reversed-phase high-performance liquid chromatographic (HPLC) system has been examined. Using methanol–water or acetonitrile–water systems as the mobile phases, a linear relationship between the volume fraction of the organic modifier, ϕ, and the capacity factor, log k′, was established for each solute over the whole examined range of methanol concentration and the limited range of acetonitrile content in the mobile phase. It was permitted to determine log k w′ values by extrapolation technique. For the system with acetonitrile the parabolic dependence of this relationship was also examined. The different correlation curves for each compound indicate selective effects upon retention due to solute–solvent and solute–stationary phase interaction. In the case of dihydroxythiobenzanilides buffering of the mobile phase at a proper pH is necessary. Studies on relationship between fungistatic activity of the compounds against the Botrytis cinerea and lipophility expressed by log k w′ have shown a great usefulness of HPLC method to evaluation of hydrophobic nature of biologically active substances in relation to biological systems.