Determination of atenolol in human urine by gas chromatography-mass spectrometry method

A sensitive and efficient method was developed for the determination of atenolol in human urine by gas chromatography-mass spectrometry (GC-MS). Atenolol and metoprolol (internal standard, IS) were extracted from human urine with a mixture of chloroform and butanol at basic pH with liquid-liquid extraction. The extracts were derivatized with N-Methyl-N-(trimethylsilyl)trifluoroacetamide (MSTFA) and analyzed by GC-MS using a capillary column. The standard curve was linear (r = 0.99) over the concentration range of 50-750 ng/mL. Intra- and inter-day precision, expressed as the relative standard deviation were less than 5.0%, and accuracy (relative error) was better than 7.0%. The analytical recovery of atenolol from human urine has averaged 91%. The limit of quantification was 50 ng/mL. Also, the method was successfully applied to a patient with hypertension who had been given an oral tablet of 50 mg atenolol.