Human plasma

In this paper the authors proposed a simple, sensitive and selective liquid chromatography–tandem mass spectrometry (LC–MS/MS) assay method for the determination of darifenacin in human plasma. This method employed solifenacin as an internal standard (IS). Analyte and the IS were extracted form 200 µL of human plasma using protein precipitation technique. The chromatographic separation was achieved on a C18 column by using a mixture of acetonitrile and 5mM ammonium formate in 0.01% formic acid (90:10, v/v) as the mobile phase at a flow rate of 1.0 mL/min. The linearity of the method was established in the concentration range 0.05–20.5 ng/mL with r2 ³ 0.99. The intra–day and inter–day precision (%CV) and accuracy results in three validation batches across five concentration levels were well within the acceptance limits. The validated method was successfully applied to a pharmacokinetic study in humans under fasting condition with 15 mg darifenacin extended release tablet.

A new reverse phase high performance liquid chromatography (RP-HPLC) method for the quantitative determination of Sitagliptin in human plasma was developed and validated as per US-FDA guidelines. The drug was spiked in the plasma and extracted with mobile phase by precipitation method. The extracted analyte was injected into an INTERSIL C18 column (150 mm × 4.6 mm, 5μm), maintained at ambient temperature and effluent was monitored at 267 nm. The mobile phase consisting of acetonitrile: methanol: buffer (2:3:5 v/v). The pH of the mobile phase was adjusted to 4.0 by using O-phosphoric acid. The flow rate was maintained at 1.0 mL/min. The developed method shows high specificity for sitagliptin. Calibration curve was plotted with a range from 25-125µg/mL (r2>0.9994). The lower limit of quantification (LLOQ) was found to be 25μg/mL. The method was validated for parameters like accuracy, precision, recovery, linearity, range, stability and sensitivity. This RP-HPLC method is suitable for determining the concentration of sitagliptin in human plasma and it was applied to routine analysis for determination of the Sitagliptin from dosage form during pharmacokinetic study.