Summary.A new sensitive and validated liquid chromatography electro spray iontandem mass spectrometry (HPLC-ESI-MS/MS) method for the quantification of Vildagliptin (VG) in rat plasma has been developed and validated using repaglinide (RG) as an internal standard (IS). The analytes were extracted by liquid-liquid extraction using ethyl acetate. Elution of the VG and IS was achieved on a reverse phase Betasil (C18 50 mm 4.6 mm ID, 5 μ) column with an isocratic mobile phase composed of acetonitrile: 2 mM ammonium acetate (90:10 v/v). The analytes monitored in the Multiple Reaction Monitoring (MRM) mode were m/z 304.2→154.0 and 453.3→230.3 for VG and RG, respectively. The calibration curve was linear in the range of 1.57-501.21 ng/mL for VG with lower limit of quantification 1.57 ng/mL. The intra run and inter run precision values are within 11.70% for VG at LOQ level.

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& A rapid, selective, and sensitive LC-MS=MS method has been developed and validated for quantification of lansoprazole (LZ) in human plasma using esomeprazole as an internal standard (IS). The analyte and IS were extracted by single solvent liquid-liquid extraction using tert-Butyl methyl ether and separated by isocratic elution on C18 analytical column with 90:10 v=v acetonitrile, and 20 mM ammonium acetate (flow rate of 1 mL=min) as the mobile phase in the positive ion mode. Selected Reaction Monitoring transitions for LZ, internal standard and their daughter ion were observed at 369, 346, 252, and 198 m=z, respectively. The lower limit of quantification was 3.997 ng=mL and total run time for the analysis was 1.2 minutes. Linear calibration was observed in the range of 3.997 ng=mL to 2002.5 ng=mL. The method was validated for its selectivity, stability, accuracy, precision, and recovery.

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New ion pair colorimetric method has been developed for the estimation of dronedrone in bulk and in tablet formulation using methyl orange dye as an ion paring complexant using pH 4 buffer. The developed method has been validated for its sensitivity and specificity. The intensity of ion pair complex of dronedrone and methyl orange found linear over the range of 2-20 µg mL-1 with a correlation coefficient of 0.9958. The inter and intraday precision, accuracy, stability, LOD, LOQ, placebo interference, robustness and ruggedness were evaluated during validation. The % RSD found for the recovery of the method resulted with low value of about 0.72-0.99; and with good precision. From the results obtained the developed method was found suitable and comparable in terms of estimating dronedrone in formulation with that of existing methods.