Standard pH values in non-aqueous mobile phases used in reversed-phase liquid chromatography

Abstract

Standard pH s values for three reference buffer solutions (0.05 mol kg −1 potassium dihydrogencitrate; 0.1 mol l −1 acetic acid +0.1 mol l −1 sodium acetate; 0.03043 mol kg −1 disodium hydrogenphosphate +0.008695 mol kg −1 potassium dihydrogenphosphate) in 10, 30, 40, 50 and 70% (w/w) acetonitrile-water mixtures at 298.15 K were determined from e.m.f. measurements of the reversible cell Pt/Ag/AgCl/ standard buffer +KCl, in acetonitrile-water/glass electrode. In order to obtain pH s values in each of the unlimited number of possible acetonitrile-water mixtures, pH s values were correlated with mole fraction, %(w/w) and %(v/v) of acetonitrile in solvent mixtures and the methodology of linear solvation energy relationship, based on the Kamlet-Taft multiparametric scales, was applied and pH s data were correlated with π *, α and β solvatochromic parameters of the acetonitrile-water mixtures.