Simultaneous quantitative determination of olmesartan and hydrochlorothiazide in human plasma and urine by liquid chromatography coupled to tandem mass spectrometry

A specific, sensitive and rapid method based on high performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) was developed for the simultaneous determination of olmesartan (OLM) and hydrochlorothiazide (HCTZ) in human plasma and urine. Solid-phase extraction (SPE) was used to isolate the analytes from biological matrices followed by injection of the extracts onto a C18 column with isocratic elution. Detection was carried out on a triple quadrupole tandem mass spectrometer in multiple reaction monitoring (MRM) mode using negative electrospray ionization (ESI). The method was validated over the concentration range of 1.00–1000 ng/mL and 5.00–5000 ng/mL for OLM in human plasma and urine as well as 0.500–200 ng/mL and 25.0–25,000 ng/mL for HCTZ in human plasma and urine, respectively. Inter- and intra-run precision of OLM and HCTZ were less than 15% and the accuracy was within 85–115% for both plasma and urine. The average extraction recoveries were 96.6% and 92.7% for OLM, and 87.2% and 72.1% for HCTZ in human plasma and urine, respectively. The linearity, recovery, matrix effect and stability were validated for OLM/HCTZ in human plasma and urine.