SEPARATION OF IONIC DRUG SUBSTANCES BY SUPERCRITICAL FLUID CHROMATOGRAPHY

The use of ion-pairing principles in supercritical fluid chromatography (SFC) is demonstrated. Using this technique, the scope of SFC can be extended to include ionic and ionizable compounds. The possibilities of ion-pair techniques and the advantages of SFC over high-performance liquid chromatography (HPLC) are discussed. The influence of different ion-pairing reagents on the selectivity was elucidated for a wide range of pharmaceutical compounds. The dependence of efficiency and selectivity on the eluent density was investigated, leading to an optimization strategy for cationic and anionic substances including matching ion-pair reagents, the stationary phase and density programming. It was demonstrated that owing to the combined influences on selectivity of the ion-pair type and the density, together with the high efficiency of SFC, optimized separations are obtained faster by SFC than by HPLC. The limitations of ion-pair SFC are mainly due to the solubility of ion-pairing reagents in the carbon dioxide-modifier mixtures. The solubility of typical ion-pairing reagents under different SFC conditions was investigated. © 1990.