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Abstract: Liquid chromatography–electrospray ionization-tandem mass spectrometry (LC–ESI-MS/MS) was used for a quantitative estimation of entecavir (EV) in human plasma using lamivudine (LM) as internal standard (IS). The method herein described is simple, sensitive, and specific. Chromatographic separation was performed on XBridge-C18, 4.6mm×50mm, 5-μm column with an isocratic mobile phase composed of 10mM ammonium hydrogen carbonate (pH 10.5):methanol (85:15 v/v), pumped at 0.3ml/min. EV and LM were detected using proton adducts at m/z 278.1→152.1 and 230.2→112.0 in multiple reaction monitoring (MRM) positive mode. Solid phase extraction method was employed in the extraction of EV and LM from the biological matrix. This method was validated over a linear concentration range of 50.0–20000.0pg/ml with a correlation coefficient (r) ≥0.9983. Intra and inter-day precision of EV was found within the range of 1.2–4.2 for EV and 4.4–4.5 for LM. EV was stable throughout three freeze/thaw cycles, bench top and postoperative studies. This method was successfully used in the analysis of plasma samples following oral administration of EV (0.5mg) in 26 healthy human volunteers. [Copyright &y& Elsevier]

Abstract: The present study aims at developing a simple, sensitive and specific liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for the quantification of pantoprazole sodium (PS) in human plasma using pantoprazole D3 (PSD3) as internal standard (IS). Chromatographic separation was performed on Zorbax SB-C18, 4.6mm×75mm, 3.5μm, 80Å column with an isocratic mobile phase composed of 10mM ammonium acetate (pH 7.10): acetonitrile (30:70, v/v), pumped at 0.6mL/min. PS and PSD3 were detected with proton adducts at m/z 384.2→200.1 and 387.1→203.1 in multiple reaction monitoring (MRM) positive mode, respectively. Precipitation method was employed in the extraction of PS and PSD3 from the biological matrix. This method was validated over a linear concentration range of 10.00–3000.00ng/mL with correlation coefficient (r)≥0.9997. Intra- and inter-day precision of PS were found to be within the range of 1.13–1.54 and 1.76–2.86, respectively. Both analytes were stable throughout freeze/thaw cycles, bench top and postoperative stability studies. This method was successfully utilized in the analysis of blood samples following oral administration of PS (40mg) in healthy human volunteers. [Copyright &y& Elsevier]