Influence of the mobile-phase modifier on the retention of some para-substituted amides; Correlation with compound lipophilicity

Abstract

The chromatographic behavior of Para-substituted amides of alpha-phenylacetic, benzoic, propanoic, and 2,2-dimethylpropanoic acid has been studied in reversed-phase thin-layer chromatography on silica gel impregnated with paraffin oil. Mobile phases used were acetone-water, methanol-water, and dioxane-water. R-M(0) values were calculated by linear extrapolation of retention to 0% organic modifier for each mobile phase. The relationships between R-M(0) Values obtained with different organic modifiers in the mobile phases are discussed. C-0 values were obtained from the slopes and intercepts of linear relationships between retention and volume fraction of modifier. Correlation between partition coefficient, log P, and R-M(0) and between log P and C-0 was examined. Results show that C-0 is a better measure of the lipophilicity of the amides than R-M(0).