Vitamin K2-4 and K2-7 estimation in nutraceutical solid dosage forms by post column derivatization with fluorescence detection

Abstract

A post column derivatization method for the estimation of fat soluble vitamins K2-4 and K2-7 was developed by reverse phase HPLC and validated as per ICH guidelines. The compounds were extracted by solvent extraction with acetone followed by evaporation in a rotary evaporator. The residue was dissolved in ethanol and injected in to a chromatograph consisting of C18 column (Waters symmetry, 150×4.6, 3.5 μ) and fluorescence detector. The derivatization reagent was prepared by dissolving 136 mg of zinc chloride, 40 mg of sodium acetate and 0.1 ml of glacial acetic acid in methanol. The mobile phase comprises of methanol:isopropyl alcohol:acetonitrile:zinc chloride buffer solution 850:90:50:10 with a flow rate of 1 ml/min. The overall percentage recoveries of five different levels were found to be 99.85 and 100.5%, respectively. The linearity of the analytical method was determined from 10% to 120% level and the linear regression coefficients were 0.9991 and 0.9995 which is well within the acceptance criteria of 0.999. The limits of detection and limits of quantification were determined based on signal to noise ratio. The established values were 0.050, 0.50 μg/ml and 0.005, 0.047 μg/ml which is much lesser than available literatue limits. The developed method can be more suitable for the estimation of K2-4 and K2-7 present in drug substances as well as drug product formulations.