Determination of sitagliptinin human plasma using protein precipitation and tandem mass spectrometry

A simple offline LC–MS/MS method for the quantification of sitagliptin in human plasma is described. Samples are prepared using protein precipitation. Filtration of the supernatants through a Hybrid-SPE-PPT plate was found to be necessary to reduce ionization suppression caused by co-elution of phospholipids with sitagliptin. The sitagliptin and its stable isotope labeled internal standard (IS) were chromatographed under hydrophilic interaction chromatography conditions on a Waters Atlantis HILIC Silica column (2.1 mm × 50 mm, 3 μm) using a mobile phase of ACN/H2O (80/20, v/v) containing 10 mM NH4Ac (pH 4.7). The sample drying after protein precipitation due to high organic content in the sample is not necessary, because HILIC column was used. The analytes were detected with a tandem mass spectrometer employing a turbo ion spray (TIS) interface in positive ionization mode. The multiple reaction monitoring (MRM) transitions were m/z 408 → 235 for sitagliptin and m/z 412 → 239 for IS. The lower limit of quantitation (LLOQ) for this method is 1 ng/mL when 100 μL of plasma is processed. The linear calibration range is 1–1000 ng/mL for sitagliptin. Intra-day precision and accuracy were assessed based on the analysis of six sets of calibration standards prepared in six lots of human control plasma. Intra-day precision (RSD%, n = 6) ranged from 1.2% to 6.1% and the intra-day accuracy ranged from 97.6% to 103% of nominal values.