Capillary zone electrophoretic method for the quantitative determination of the beta-blocker atenolol in human urine

A simple capillary zone electrophoresis method was developed for the quantitation of the beta-blocker 4-[2-hydroxy-3-[(1 -methylethyl)amino]propoxy] benzeneacetamide, atenolol. The electrophoretic separation was performed using a 78 cm x 75 mu m I. D. fused silica capillary. The electrolyte consisted of a buffer Na2HPO4 (25mM)-Na2B4O7 (25 mM) (50-50; V/V), pH 9.7. The introduction of the sample was made hydrostatically for 25 s and the running voltage was 20 KV at the injector end of the capillary. Photometric detection was used and a wavelength of 214 nm. The method was applied to the determination of atenolol in urine samples obtained from a hypertensive patient under medical treatment with the pharmaceutical formulation ''Tenormin 100 mg'' (atenolol 100 mg), another patient under treatment with the pharmaceutical combination ''Tenoretic'' (atenolol 100 mg + chlorthalidone 25 mg), and also in urine samples obtained from a healthy volunteer after the ingestion of a 100 mg atenolol tablet, ''Tenormin 100 mg''. Using a simple solid phase extraction, a recovery of 70.69+/-3.27% and a very good separation from the urine matrix are achieved. A good reproducibility, linearity, and accuracy are obtained, and a quantitation limit of 0.1 mu g/mL in urine, allows the method to be applied to pharmacokinetic studies of the compound.