High-performance liquid chromatographic determination of propranolol and 4-hydroxypropranolol in serum.

A simple, sensitive and selective high performance liquid chromatographic method for the analysis of propranolol and its major metabolite 4-hydroxypropranolol is developed. The drugs and the internal standard, quinidine, were extracted from serum with ether at pH 10. The latter was evaporated and the residue was dissolved into phosphoric acid solution. Propranolol, 4-hydroxypropranolol and quinidine were eluted from 5 microns, C-18 reversed phase column with a mobile phase consisting of acetonitrile-methanol-phosphoric acid at pH 4 and detected with fluorescence detector. Quantification was achieved by measuring the peak height ratio of each drug to the internal standard. Interference due to either biological constituents of serum or other propranolol metabolites such as n-desisopropyl propranolol and propranolol glycol was absent. The mean percentage recoveries for serum samples spiked with propranolol and 4-hydroxypropranolol were 94.7 and 98.4%, respectively. Detection limits were 10 ng/ml for propranolol and 5 ng/ml for 4-hydroxypropranolol. Within-day coefficients of variation ranged from 3.2-6.9% for propranolol and 0.8-6.2% for 4-hydroxypropranolol.