Combined Use of Normal and Reversed Phase Thin Layer Chromatography in the Screening for Basic and Quaternary Drugs

Abstract

Abstract The combined use of normal and reversed phase thin layer chromatography in drug screening is evaluated by the mean list length method. A reversed phase system, involving RP-18 plates and aqueous hydrochloric acid - methanol as a mobile phase, is shown to be an effective complementary pair to basic medium-polar normal phase systems. With a set of 140 basic and quaternary drugs, a mean list length of 1.8 is obtained for a TLC/RPTLC pair. The combination is also applicable to hydrophilic drugs extracted as bis(2-ethyl-hexyl)phosphate ion-pairs.