Objective: A unique liquid chromatog.-tendon mass spectrometric technique for the determination of metformin and vildagliptin in K3EDTA human plasma was developed and verified as per the USFDA guidelines of bioanal. Methods: The chromatog. separation was achieved using a Cosmosil CN (150 x 4.6 mm, 5μm) column with an isocratic elution pattern using 10 mM ammonium formate (pH 5.0) and methanol in the ratio of 30:70 volume/volume as a mobile phase. A mass spectrometer coupled with an electrospray ionization (ESI) source operating in the pos. ion was used for detection. Data were obtained in the multi-reaction monitoring (MRM) acquisition mode. Metformin D6 and vildagliptin D7 were used as internal standards, with the flow rate at 1.0 mL/min throughout the experiment The drugs were extracted by solid phase extraction (SPE) packed with Phenomenex Strata-X. Extraction of the drug was achieved using methanol: 5 mM sodium lauryl sulfate solvent mixture in equal proportions. Results: The retention time for MET and VLG were 3.2 and 3.8 min individually. The drugs were extracted by SPE with good recovery of 89.44% and 87.57% for metformin and ISTD and 92.26% and 89.58% for vildagliptin and ISTD, resp. Sample elution was performed using solid phase extraction (SPE), and this technique produced very pure extracts with good recovery rates. A liner calibration curve was found in the range of 0.5-400 ng/mL for MET and 0.2-160 ng/mL for VLG with a correlation coefficient r2 > 0.99. Conclusion: The aforementioned technique is reliable and effective for monitoring bioequivalence investigations in human participants.

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