Determination of ten beta-blockers in urine by micellar electrokinetic capillary chromatography.

beta-Adrenergic blocking agents are of therapeutic value in the treatment of migraine and various cardiovascular disorders (angina pectoris, cardiac arrhythmia, hypertension). Owing to their sedative effect, they are also used as doping agents in sport. A characteristic feature of beta-blockers is the alkanolamine side-chain terminating in a secondary amino group. The pKa values vary from 9.2 to 9.8. Because some beta-blockers are hydrophilic and some lipophilic, simultaneous determination is difficult. In this work, a method based on micellar electrokinetic capillary chromatography (MECC) was developed for the separation and determination of beta-blockers. The 0.08 M phosphate buffer (pH 7.0) solution contained 10 mM N-cetyl-N,N,N-trimethylammonium bromide (CTAB). Ten parent beta-blockers in human urine could be separated in a single run and determined quantitatively by the internal standard (2,6-dimethylphenol) method. Neither endogenous compounds in urine nor caffeine and its metabolites interfered with the analysis. The clean-up procedure for urine consisted of a simple filtration through 0.5-microns PTFE membranes. The MECC method exhibited good repeatability and a linear range of 25-150 micrograms/ml. The method was applied to determination of oxprenolol in real samples.