Mass Spectroscopy.

A specific, sensitive and rapid LCMS/MS method was developed for simultaneous determination of olmesartan and hydrochlorothiazide in human plasma using olmesartan D4 and hydrochlorothiazide 13C6 as internal standards. Solid-phase extraction (SPE) method was used to extract the analytes from biological matrix. Analysis was carried out on phenomenex Luna C18 column with a flow rate of 0.600 mL/minute with 80% flow splitting. Detection was carried out on a triple quadrupole linear mass spectrometer, equipped with turbo ion spray source. The method was validated over the concentration range of 32.32 ng/mL to 2676.60 ng/mL for olmesartan and 5.12ng/mL to 423.83ng/mL for hydrochlorothiazide. Olmesartan and hydrochlorothiazide were found to be stable upto 75 days in K3EDTA based Human Plasma at -20ºC. Inter and intra-batch precision of olmesartan and hydrochlorothiazide were less than 15% and the accuracy was within 85–115% in plasma.  The mean % recovery was 53.09 % for olmesartan and 59.12 % for hydrochlorothiazide in human plasma. The stability of olmesartan and hydrochlorothiazide in plasma were confirmed up to five freeze-thaw cycles at -20°C and on bench up to 24 hours and 15 minutes at ambient temperature. The method was validated satisfactorily and was suitable for the quantitation of olmesartan and hydrochlorothiazide from plasma samples in a pharmacokinetic study.