A simple, sensitive, precise and accurate method for simultaneous estimation of metformin and sitagliptin from human plasma was developed and validated. Samples extracted from plasma using acetonitrile were separated on an SCX column and estimated using API 4000 Mass Spectrometer in the positive atmospheric pressure ionization mode (Turboionspray) by following multiple reaction monitoring transitions for both parent and daughter ions. A linear calibration plot was achieved for both the analytes in the concentration ranges of 10-2,206 ng/mL (for metformin) and 3-800.5 ng/mL (for sitagliptin) prepared in K2EDTA pooled plasma. Mean recovery for metformin was 92% and for sitagliptin was 104.5%. It is a fully validated method and successfully applied for estimation of these drug molecules during biostudies.

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Background: A new LC-MS/MS method for the simultaneous determination of lamivudine, zidovudine, and nevirapine in human plasma is developed using column-coupling technique. Method: Labeled compound of respective analyte was used as an internal standard. After extraction from 100 μL plasma by solid phase extraction method, analytes were separated on a C18 column coupled with a cation exchange column. Total run time was 4.5 min. A tandem mass spectrometric detection was conducted using multiple reaction monitoring under positive ionization mode with an electrospray ionization interface. The method was validated as per the FDA guidelines over the concentration range of 9.47-1466.67 ng/mL for lamivudine, 10. 32-1600.00 ng/mL for zidovudine, and 15.05-2426.67 ng/mL for nevirapine. Results: Precision was in the range 0.86-5.77 (intraday) and 1.92-8.19 (interday) while accuracy was 93.25-104.36 % (intraday) and 96.83-103.28 % (interday). Stabilities of stock in aqueous solutions and in plasma were also determined. Conclusion: The method can be applied to the pharmacokinetic study of a combination treatment.

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