High‐performance liquid chromatographic determination of metoprolol and α‐hydroxymetoprolol concentrations in human serum, urine, and cerebrospinal fluid

A sensitive and simplified high‐performance liquid chromatographic procedure was developed for the simultaneous quantification of metoprolol and α‐hydroxymetoprolol in human serum, as well as cerebrospinal fluid and urine. Following protein precipitation with trichloroacetic acid, the sample was alkalinized with 1 M NaOH and extracted with dichloromethane. The mobile phase consisted of acetonitrile‐water (50:50) containing 0.005 M 1‐heptanesulfonic acid in 0.001% acetic acid. Using pronetalol as an internal standard, compounds were quantitated using fluorescence detection at 230 nm with a 300‐nm emission filter and 0.02 AUFS. Extraction recovery is ∼80% for both compounds. The lower limits of detection are 5 ng/mL and 4 ng/mL for metoprolol and α‐hydroxymetoprolol, respectively.