Turkish Journal of Chemistry




A selective and sensitive ultra performance liquid chromatography-tandem mass spectrometry method was developed for the simultaneous determination of losartan (LOS), EXP-3174, which is an active metabolite LOS carboxylic acid, and hydrochlorothiazide (HCTZ) in human plasma. Solid-phase extraction was carried out on Oasis HLB cartridges with 100 $\mu $L of plasma to give an extraction recovery in the range of 88.5%-102.5% for the three analytes. Chromatography on a BEH C18 column afforded baseline separation of all the analytes within 2.4 min using 1.0% formic acid in water and acetonitrile (15:85, v/v) as the mobile phase. Quantitation was performed with multiple reaction monitoring in the negative ionization mode. The response of the method was linear over a dynamic range of 0.5-500, 1.0-750, and 0.25-150 ng/mL for LOS, EXP-3174, and HCTZ, respectively. Extent of signal suppression/enhancement was examined through postcolumn infusion. The effect of matrix components was evaluated by postextraction spiking and calculation of the slope of calibration lines. The method was successfully applied to a bioequivalence study of 50 mg losartan and 12.5 mg hydrochlorothiazide tablet formulation in 65 healthy human subjects. Reproducibility of the method was shown by reanalysis of 213 incurred samples.


Losartan, EXP-3174, hydrochlorothiazide, solid phase extraction, UPLC-MS/MS, human plasma

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