SUMMARYLiterature data on activity coefficients of various solutes in water, of some tetraalkyl compounds in methanol-water mixtures and of water in organic solvents have been correlated with the product of the molecular surface area of the solute and the solute-solvent interfacial tension at ambient temperature. The conditions for which this relationship holds are examined.The retentions of apolar solutes have been measured on LiChrosorb RP-IS using methanol-water mixtures as eluents at 25°C. The results are discussed in terms of a monolayer adsorption model (according to Locke-Everett) and in terms of the adsorption model based on the solvophobic interaction theory. The important role of solute activity coefficients in the eluent on solute retention is shown quantitatively. The affinity of the adsorbent towards solutes is shown to be a result of apolar interactions in the RP-IS phase and of polar interactions in the interfacial layer of adsorbed methanol_ The influence of both contributions is illustrated.

SUMMARYRetention data of methylbenzenes, n-alkylbenzenes, fused arenes, polyphenyls, chlorobenzenes, -anilines and -phenols and some polar monosubstituted benzenes have been measured on LiChrosorb RP-18, using methanol-water mixtures as eluents at 25'C.The important effect of solute activity coefficients in water on capacity ratio (k) data, holding for water as eluent, and on partition coefficients in the octanol-water system (PO,,_) is shown. The log k-log I',,,,_ correlation is improved by using (1inearIy extrapolated) log X-values in water, instead of those in methanol-water mixtures. At similar log Pact_ values the log k values of the polar benzenes are slightly higher than those of the lipophilic compounds_ Consequently, two log k-log Pa,,_ regression equations are proposed. Steric and intramolecular electronic effects on the values for log P,,,,_ of halogenated anilines and phenols are described quantitatively. The results cast doubt on the reliability of Rekker'sf-method for the prediction of log PO,,_ values of highly substituted aromatic compounds_