Objective: The present study is aimed to develop and validate an Ultra-Fast Liquid Chromatography-Diode Array Detector (UFLC-DAD) method for the quantification of vitamin K2 as Menaquinone-4 (MK-4) in rabbit plasma. Method: Standard solutions and spiked plasma samples of MK-4 and Internal Standard (IS) were prepared from primary stock solutions of 1mg/ ml concentration in ethanol each. Protein precipitation was carried out for the MK-4 and IS extraction from plasma spiked samples. Chromatographic separation was employed using Isopropyl Alcohol and Acetonitrile (50:50 v/v) as mobile phase and a C-18 column with 1ml/min flow rate and a run time of 10 mins. Detection was carried out in the range 190-600 nm with 269 nm set as a reference wavelength. Result: The retention times of MK-4 and IS were at 5.5 ± 0.5 mins and 8 ± 0.5 mins respectively. Calibration curve for MK-4 was found to be linear in the range of 0.374 to 6 µg/ ml with an R 2 value of 0.9934. The % RSD for accuracy was <15%, inter and intraday precisions were <10%. The samples were found to be stable throughout the study. Conclusion: This method can be applied to the estimation of MK-4 in rabbit plasma using UFLC-DAD.

A simple, accurate, rapid, and sensitive method using liquid chromatographic-quadrupole time of flight mass spectrometric method has been developed and validated for the simultaneous estimation of telmisartan (TS) and hydrochlorothiazide (HCTZ) in marketed tablet formulation utilizing olmesartan medoxomil (OSM) as internal standard. Sample preparation employed a simple solvent extraction technique. Chromatographic separation of analytes and internal standard, OSM, has been achieved on a Thermo Accucore TM C18 column (50 × 4.6 mm i.d, 2.6 µ) using gradient elution with 10 mM ammonium acetate solution and acetonitrile at a flow rate of 0.4-0.6 ml/minute. Mass spectrometric detection was achieved by combined electrospray ionisation as interface in negative polarity mode. Upon MRM ion scan, precursor and product ions were observed at m/z 513.20, 287.11 for TS, m/z 295.94, 204.97 for HCTZ, m/z 557.18, m/z 401.18 for Olmesartan medoxomil, respectively. The method was found to be linear in the range 0.20 to 4.01 ng per injection volume (5 µl) for TS and 0.06 to 1.25 ng per injection volume (5 µl) for HCTZ with precision values (as coefficient of variance) <2%. The assay recovery values of TS and HCTZ were found to be 98.9% and 99.6%, respectively.