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 curveswere linear over the concentration range 15–500 ng/ml. Intraand
inter-day precision values formetoprolol 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 100mg metoprolol.