A fluorimetric liquid chromatographic method for the determination of propranolol in human serum/plasma

A simple, rapid, and sensitive fluorimetric-high-performance liquid chromatographic method for the determination of propranolol in human serum/plasma has been developed, without the need for solvent extraction. The procedure required 200 μl of serum/plasma, and the addition of 1 ml of acetonitrile for protein precipitation followed by vortexing and centrifugation at 10 000 g. The clear supernatant was evaporated to dryness under a stream of nitrogen at 50 60°C, the residue was reconstituted in 100 μl of methanol, and a 90 μl portion was injected onto the high-performance liquid chromatograph for propranolol quantitation. Chromatography was accomplished using a Hypersil^® cyano column, a mobile phase of acetonitrile - aqueous acetic acid (1%) containing 0.2% triethylamine (35:65, v/v) (pH 3.6), a flow rate of 1.5 ml min⁻¹, a fluorescence detector set at an excitation wavelength of 230 nm and an emission wavelength of 340 nm, and using pronethalol as the internal standard. Retention times for pronethalol and propranolol were 7.5 min and 9.5 min, respectively. Standard curves were linear in the range 5–200 ng ml⁻¹. Relative standard deviations for both inter-day and intra-day precision analysis were less than 7% for serum. No interference was observed from endogenous serum/plasma components. Specificity was shown for some, but not all, commonly coadministered drugs tested. The advantages of this method include good precision, low sample volume, good reproducibility and recovery, and high sensitivity.