RETENTION BEHAVIOR OF AROMATIC SULFONIC-ACIDS IN REVERSED-PHASE ION-PAIR LIQUID-CHROMATOGRAPHY WITH METHANOL AND ACETONITRILE AS ORGANIC MODIFIERS

The capacity factors of phenylamine- and naphthylaminesulphonic acids in reversed-phase ion-pair liquid chromatography were measured. The eq uations log k' = log k(w) - Sphi and log k' = log k(w) + Aphi2- Sphi t o describe the effects of methanol and acetonitrile concentration were compared. It has been observed that the effect of organic modifier co ncentration up to phi = 0 on retention follows the empirical equation log k' = log k(w) - Sphi. It was found that the effect of acetonitrile on retention is stronger than that of methanol, which is the same as the order of their elution strengths observed in RP-HPLC.