Analysis of polymyxin B sulfate by capillary zone electrophoresis with cyclodextrin as additive Method development and validation

A capillary zone electrophoresis method for analysis of polymyxin B sulfate is described. In this method, triethanolamine (TEA)-phosphate buffer at pH 2.5 was employed to reduce the adsorption of analyte onto the capillary wa ll. Methyl-beta-cyclodextrin (M-beta-CD) and 2-propanol (IPA) were found to be necessary for selectivity enhancement. In order to optimize the method and to control its robustness, a central composite design was performed wit h four parameters, i.e. concentration of M-beta-CD, TEA, IPA and buffer pH. The optimal separation conditions were as follows: capillary, 55 cm (50 mu m I.D., 47 cm effective length); 130 mM TEA-phosphate buffer (pH 2.5) cont aining 5 mM M-beta-CD and 5% IPA; 24 kV (51 mu A) applied voltage; column t emperature, 20 degrees C. Further, linearity and limits of detection quanti fication were examined. Three commercial samples were analyzed quantitative ly. (C) 2000 Elsevier Science B.V. All rights reserved.