A rapid and sensitive liquid chromatography-tandem mass spectrometry method has been developed and validated for the determination of febuxostat in human plasma. The liquid-liquid extraction technique was used for the extraction of febuxostat from human plasma using trandolapril as the internal standard (IS). Chromatography was performed on a ultra-performance liquid chromatography (UPLC) BEH C18, 50 mm X 2.1 mm, 1.7 µm particle size column, with the mobile phase consisting of 0.1% formic acid and acetonitrile (in a 25:75 ratio), followed by detection using mass spectrometry. The method involves a simple reversed isocratic chromatography condition and mass spectrometry detection, which enables detection at sub-microgram levels. The method was validated and the lower limit of quantification for febuxostat was found to be 0.075 µg/ml. The mean recovery for febuxostat ranged from 100.9 to 106.5%. This method increased the sensitivity and selectivity; resulting in high-throughput analysis of febuxostat using commercially available IS for pharmacokinetic, bioavailability, and bioequivalence studies, with a chromatographic run time of 1.5 min only.

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A rapid and sensitive liquid chromatography tandem mass spectrometry method has been developed and validated for the determination of the active metabolite (R-138727) of prasugrel in human plasma. Because R-138727 contains a thiol group, it requires stabilization by derivatizing with N-ethyl maleimide. Commercially available trandolapril was used as the internal standard (IS). The derivatives of R-138727 and IS were extracted from human plasma using a liquid-liquid extraction technique. Chromatography was performed on a Hypurity C18, 5 µ (50 mm × 4.6 mm, i.d.) column, with the mobile phase consisting of acetonitrile and 10 mM ammonium formate (pH 3.0, 50:50 V/V), followed by detection using mass spectrometry. No significant endogenous peaks corresponding to R-138727 or IS were detected in the blank human plasma samples and no significant matrix effect was observed for R-138727 and IS in the human plasma samples. The mean recovery for R-138727 ranged from 90.1 to 104.1%, with the lower limit of quantification set at 1 ng/ml. Linearity was established for concentrations in the range of 1.0-500.12 ng/ml, with a coefficient of determination (r(2) ) of 0.9958. The derivatized R-138727 was stable in human plasma for 3 months at -20 °C. This method increased the sensitivity and selectivity, resulting in high-throughput analysis of R-138727 using trandolapril as the IS in pharmacokinetic and bioequivalence studies, with a chromatographic run time of 3.7 min.

A rapid and sensitive method for the determination of miglitol in human plasma was developed using ultra-performance liquid chromatographic separation with tandem mass spectrometry detection. The preparation of samples required a deproteinization step with acetonitrile. Chromatography was performed on a 5 µ (50 mm × 4.6 mm, ID.) C18 inertsil column, with the mobile phase consisting of acetonitrile 2 mM and ammonium acetate (pH 3.5) with formic acid. Detection was performed using an Applied Biosystems Sciex API 2000 mass spectrometer set at unit resolution in the multiple reaction monitoring mode. Electrospray ionization was used for ion production. The mean recovery of miglitol was 88.9%, with the lower limit of quantification set at 150 ng/mL. Linearity was established for concentrations in the range of 150-4000 ng/mL, with a coefficient of determination (r(2) ) of 0.9981. This assay method makes use of the increased sensitivity and selectivity of tandem mass spectrometric detection, resulting in high-throughput analysis of miglitol for bioequivalence studies.