Chiral separations of selected pharmaceuticals on avidin column

An unexplored commercially available avidin protein column was investigated for chiral separation of selected pharmaceuticals. Mobile phase compositions such as pH, buffer strength, and organic modifier were varied to affect separation of racemic mixtures. Baseline resolution of enantiomers were successfully achieved for thalidomide, glutethimide, primaquine, aminoglutethimide, hydroxyzine, chlorthalidone, and pyridoglutethimide. Partial separation of enantiomers were achieved for oxazepam, lorazepam, verapamil, and hexobarbital. Separation conditions of each racemate were optimized so that the methods can be used for the analysis of racemic pharmaceuticals. The pH and organic modifier of mobile phase played a greater role than buffer strength in the separation of individual racemate. The presence of aromatic rings and carbonyl functions directly attached to the chiral center of an analyte may play an important role in recognizing a specific site in the protein bonded phase.