Enantioselective separation of thalidomide on on immobilized αl-acid glycoprotein chiral stationary phase

An easy and rapid enantioselective separation for assay of racemic thalidomide on an immobilized alpha (1)-acid glycoprotein chiral stationary phase (GPA CSP) is described. The effects of tetrahydrofuran (THF) as organic modifier, buffer concentration to control the ionic strength, and mobile phase pH were studied. These variations have consequences in terms of chromatographic retention (k), resolution (R-s), selectivity (alpha), and peak asymmetry (USP tailing factor). The main condition affecting chromatographic retention was mobile phase pH. At pH 4.5, no separation of thalidomide enantiomers wets achieved whereas at pH 7.0 chiral separation was optimum. Peak tailing was directly related to changes in pH and to addition of THF as mobile phase modifier. Results also indicated that the resolution factor is THF concentration-dependent, and that the separation factor (alpha) is the best parameter for evaluating enantioselectivity. The best mobile phase was pH 7.0, 30 mM ammonium acetate containing 0.3% THF. Under these conditions validation including linearity recovery, and precision was performed. The suitability of this method has been successfully proved in a limited in-vivo study after intravenous administration of thalidomide to a New Zealand male rabbit.