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

Abstract

β-Adrenergic blocking agents are of therapeutic value in the treatment of migraine and various cardiovascular disorders (angina pectoris, cardiac arrythmia, hypertension). Owing to their sedative effect, they are also used as doping agents in sport. A characteristic feature of β-blockers is the alkanolamine side-chain terminating in a secondary amino group. The p K a values vary from 9.2 to 9.8. Because some β-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 β-blockers. The 0.08 M phosphate buffer (pH 7.0) solution contained 10 m M N-cetyl-N,N,N-trimethylammonium bromide (CTAB). Ten parent β-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- μm PTFE membranes. The MECC method exhibited good repeatability and a linear range of 25–150 μ/ml. The method was applied to determination of oxprenolol in real samples.