High-performance ion-pair partition chromatography of sulfa drugs. Study and optimization of chemical parameters

High-performance ion-pair partition chromatography is shown to be a versatile, efficient method for separating sulfonamides. For a group of fourteen sulfa drugs varying widely in pKA and hydrophobicity, the effect of mobile phase composition, counterion composition, pH, and ionic strength on their ion-pair partition chromatographic separation using tetrabutylammonium as the counterion and n-butanol-n-heptane as the mobile phase is shown. Wide variation in k' and a is possible by changing these parameters. Silica columns coated with buffered aqueous solutions of tetrabutylammonium sulfate resulted in efficiencies of 4000-6000 theoretical plates per 25 cm. These columns are stable for long periods of time, and can be stripped and re-used in the adsorption mode with little or no loss in efficiency. Several chromatograms are presented in order to illustrate the performance of ion-pair partition chromatography.