EFFECT OF BUFFER SOLUTION PH ON THE ELUTION AND SEPARATION OF BETA-BLOCKERS BY MICELLAR ELECTROKINETIC CAPILLARY CHROMATOGRAPHY

Study was made of the effect of the pH of phosphate buffer (0.08 M) co ntaining 15 mM cetyltrimethylammonium bromide as surfactant on the elu tion order of eleven widely used beta-adrenergic blocking agents. In t he pH range 6.0-7.8 the elution order of six of the beta-blockers rema ined the same, while the order of five of them changed. Sotalol eluted as the sixth compound at pH 6.8 and migrated more quickly with increa sing pH. Below pH 7.0 labetalol eluted before propranolol and above pH 7.0 afterwards. Likewise, the order of elution of atenolol and timolo l was reversed at pH 7.0. The pH also affected the resolution; the bes t resolution values were achieved between pH 6.6 and 7.0 and between p H 7.4 and 7.8. The relationship between the structure of the beta-bloc kers described by molecular and molecular connectivity indices and the elution order and separation of the beta-blockers in micellar electro kinetic capillary chromatography at varying pH of the buffer solution is discussed.