Determination of the lipophilicity of some new thiosemicarbaside derivatives by reversed-phase thin-layer chromatography

In this study, the chromatographic behavior of a newly synthesized series of 1,4-disubstituted thiosemicarbazide derivatives and products of their dehydrocyclization is presented. These compounds have been subjected to this study because they exhibit antimicrobial activity. The compounds have been chromatographed on RP-18 and on cyano-bonded silica chromatographic phases with eluents containing water and an organic modifier (methanol, dioxane, acetone, acetonitrile or tetrahydrofuran) of various concentrations. Statistically proved linear relationships between the retention parameter (RM) and the concentration of organic modifier in the mobile phase allow the extrapolation procedure to obtain RM0 for investigated compounds. The correlations between both the values of the intercept (RM0 ) and the slope (S) from the linear equation, taken as a measure of the lipophilicity, were calculated. The experimentally established parameters of lipophilicity (RM0 ) were compared with the log P values calculated by use of four different software packages. The values of the correlation coefficients of these relationships are higher for the cyanopropyl phase than for RP-18. Moreover, in this work the influences of different mobile phase modifiers and adsorbent layers on experimentally obtained lipophilicity parameters were analyzed and compared. Generally, the best correlations were obtained for systems with the cyanopropyl-bonded stationary phase in comparison with RP-18.