Reversed-phase ion-pair partition chromatography of carboxylates and sulphonates.

A reversed-phase partition chromatographic system for separation of organic anions as ion pairs with quaternary ammonium ions has been developed. Commercial, hydrophobized silica supports are used with 1-pentanol as stationary phase and aqueous solutions of tetrabutylammonium (TBA) as mobile phase. The separation of the aromatic sulphonates and benzoic acid derivatives is demonstrated. The use of the TBA concentration of the mobile phase to regulate the capacity factor of the anions, as a means of improving separation by gradient elution and direct injection of large sample volumes, is demonstrated. The isolation of nicotinic acid from human serum samples is shown.