The application of factor analysis to solvatochromic parameters and pHs values for the standardization of potentiometric sensors in mobile phases used in liquid chromatography

The pH(s) values for reference buffer solutions in aqueous acetonitrile, methanol, and tetrahydrofuran mixtures used as mobile phases in LC were subjected to factor analysis in order to discover the number of factors which affect the variation with the percentage of organic co-solvent of the whole data sets. Afterwards, target factor analysis was used to identify these factors. The pH(s) values were correlated with the solvatochromic parameters (pi*, alpha, beta, and E-T) Of the hydro-organic mixtures according to the results obtained using these chemometric techniques. An equation is proposed which permits the calculation of pH(s) values in any aqueous acetonitrile, methanol, or tetrahydrofuran mixtures, and thus accurate pH measurements can be made in these media as well as in water. An overview of the effects on pH(s) values of preferential solvation in these media is also presented. (C) 1999 Elsevier Science B.V. All rights reserved.