ROLE OF THE SOLVENT IN RPLC - INFLUENCE OF THE NATURE OF ORGANIC MODIFIERS OF THE MOBILE-PHASE IN NONAQUEOUS REVERSE-PHASE LIQUID-CHROMATOGRAPHY

Following the common previsions from solvophobic and partition theorie s, it is shown that the retention of solutes versus the percentage of organic modifier can be correlated with the variation of mobile phase surface tension versus the percentage of organic modifier in non-aqueo us reverse phase liquid chromatography (NARP). This is true for mixtur es of acetonitrile or nitromethane in methanol but not for THF, aceton e, methylene chloride or chloroform, (solvents with dielectric constan ts lower than 30). In the latter cases, the parameter affecting the re tention is the dielectric constant of the mobile phase. A conformation al modification of the alkyl chain of the stationary phase results fro m the use of this type of solvent. In choosing the organic modifiers t o be used in NARP in regard to their properties, the Kaelble triangle appears to be more efficient than the well known Snyder triangle. Fina lly, the molecular interactions between the organic modifiers that con stitute a non-aqueous ternary mobile phase (MeOH/MeCN/X) could be rati onalized by the examination of their partial solubility parameters.