Investigation of Pressure-Induced Changes in the Chromatographic Selectivity of Methyl and Ethyl Orange on Silica Gel

Abstract
With water as the solvent and two azo dyes as the exemplary solutes, the modification of selectivity through pressure-induced changes in column equilibria has been shown to be significant using a chromatograph capable of going to 4000 kg/cm2. Data from high-pressure conductance, spectroscopy, adsorption chromatography, and steric-exclusion chromatography indicated that the primary contribution to the pressure shifts in selectivity was occurring in the bulk solution. An explanation correlating the various experimental observations is offered.