Gas chromatography–mass spectrometry method for determination of metoprolol in the patients with hypertension

A sensitive and efficient method was developed for determination of metoprolol in human plasma by gas chromatography–mass spectrometry (GC–MS). Metoprolol and atenolol (internal standard, IS) were extracted from human plasma with a mixture of ethylacetate and diethylether at basic pH with liquid–liquid extraction. Calibration curves were linear over the concentration range 15–500 ng/ml. Intra- and inter-day precision values for metoprolol in human plasma were less than 6.4, and accuracy (relative error) was better than 8.8%. The analytical recovery of metoprolol from human plasma averaged 91.20%. The limits of detection (LOD) and quantification (LOQ) of metoprolol were 5.0 and 15 ng/ml, respectively. Also the developed and validated GC–MS method was successfully applied to three patients with hypertension who had been given an oral tablet of 100 mg metoprolol.