QUANTIFICATION OF INTERMEDIATE, UNKNOWN IMPURITIES AND Z ISOMER IN ENTACAPONE API BY HPLC

Simple, linear and accurate method was developed for the quantification of Z-isomer impurity and 3, 4-dihydroxy-5-nitrobenzaldehyde intermediate in entacapone active pharmaceutical ingredient by using high performance liquid chromatography. Separation between impurities and Entacapone was achieved on Phenomenox Kinetex C18, (100 x 4.6) mm, 2.6 micron column. Mobile phase consisted of 0.1% Orthrophosphoric acid in water: Methanol in ratio 58:42:0.1 in isocratic mode for RSD of standard. Gradient method was used for sample preparation and blank with flow rate of 0.8 ml/min at 300 nm and column oven temperature at 50°C. RSD for standard preparation under system precision and percentage recovery was observed with in acceptance range. RSD for retention time was observed 0.05% which shows reproducibility during replicate injections. Limit of detection and limit of quantification was achieved at 0.1 ppm and 0.2 ppm level respectively which indicates the lowest level of detection and quantification. The linearity range was achieved from 0.2 ppm to 0.75 ppm level for entacapone, Z-isomer and intermediate. The method was applied for quantification of Z-isomer, intermediate and any unknown impurity of entacapone API