Isohydric solvents in liquid-solid column chromatography : Importance for the reproducibility of chromatographic separations and application to the experimental determination of mobile phase polarity

Abstract

Isohydric solvents are defined as solvents with water contents corresponding to the same activity of the adsorbent. The influence of the water content of the mobile phase on the activity of the adsorbent and on the reproducibility of separations was studied. A practical means of determining suitable water contents of solvents and solvent mixtures is described. The use of isohydric solvents greatly improves the reproducibility of chromatographic separations. The water contents of isohydric solvents may constitute a scale of relative polarities. In mixtures of isohydric solvents, good linear relationships were obtained between solute capacity factors ( k′) and the inverse of the molar fraction of water (1/ N H 2O isoh).