On-Line Concentration Methods for Analysis of Fat-Soluble Vitamins by MEKC

A fast, selective and sensitive reversed phase liquid chromatographic method employing a C-18 column has been developed and validated for simultaneous analysis of four impurities of duloxetine hydrochloride, an antidepressant drug, viz., (S)-N,N-dimethyl-3-hydroxy-(2-thienyl)-propanamine, phenolic impurity, 1-napthol and duloxetine succinamide. Good separations were achieved by a gradient elution with mobile phase consisting of a mixture of phosphate buffer 14 mM containing 0.1% of sodium octanesulfonate, pH 3.0, at a flow rate of 0.8 mL min^?1. The detection was at 220 nm. The method was validated for precision, linearity and accuracy. Finally, the developed method was used to quantify the impurities during stability sample analysis of duloxetine hydrochloride drug products.