Determination of nine beta-blockers in serum by micellar electrokinetic capillary chromatography

beta-Adrenergic blocking agents are used for the treatment of angina pectoris, cardiac arrhythmia, hypertension, anxiety attacks, thyrotoxicosis, migraine and glaucoma. Owing to their sedative effect, they are also used as doping agents in sport. All beta-blockers have an alkanol amine side chain terminating in a secondary amino group in their structure. 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 in serum. The phosphate buffer 0.08 M (pH 6.7) solution contained 15 mM N-cetyl-N,N,N-trimethylammonium bromide. Nine parent beta-blockers could be separated in a single run and the concentrations determined by internal standard (ephedrine) method. The simple clean-up procedure consisted of enzyme hydrolysis (Helix pomatia), protein precipitation, and filtration through 0.5-microns PTFE membranes. The MECC method exhibited good repeatability and a linear range of 75-300 micrograms/ml. The method was successfully applied after concentration to the determination of propranolol in real samples.