Determination of Content and Related Substances of Methylparaben Sodium by HPLC

OBJECTIVE To establish a method to determine the content and related substances of methylparaben sodium. METHODS HPLC was adopted on a Shim-pack VP-ODS C₁₈ column (250 mm×4.6 mm, 5 μm) using an isocratic mobile phase consisting of methanol-0.1% acetic acid solution (60∶40) with a flow rate of 1.0 mL·min^-1. The column temperature was kept at 35 ℃ and the detection wavelength was set at 254 nm. RESULTS The separation of methyl parahydroxybenzoate and other impurities was achieved within four times of the major peak retention time. The concentration-response relationship was linear over the range of 21.64-194.8 mg·mL^-1(r=1.000). The average recovery was 99.5%(RSD=0.64%, n=9) and the limit of detection was 0.214 4 ng. The solution was stable for 24 h. CONCLUSION The method is specific, accurate, sensitive and suitable for the determination of content and related substances of methylparaben sodium.