Simultaneous content determination of benzoic acid and salicylic acid in a new concentrated benzoic acid and salicylic acid ointment by RP-HPLC

AIM To establish a method for the simultaneous content determination of benzoic acid and salicylic acid in a new concentrated benzoic acid and salicylic acid ointment by RP-HPLC.METHODS A Kromasil-C_(18)chromatographic column(150 mm×4.6 mm,5μm)was used;the mobile phase was V(methanol):V(0.02 mol·L~(-1) KH_2PO_4,the pH value was adjusted to 3.1 with H_3PO_4 solution)=50:50;the determination wave length was 280 nm;the flow rate was 1.0 mL'min1 and the column temperature was 20℃.RESULTS The linear ranges of benzoic acid and salicylic acid were 96-144 mg·L~(_1)(r=0.9995)and 48-72 mg·L~(-1)(r=0.999 7),respectively.Their average recoveries were within 99.6%-100.6%and 99.4%-100.2%.respectively.CONCLUSION The method is simple, accurate,reproducible and suitable for the determination of benzoic acid and salicylic acid levels in a new concentrated benzoic acid and salicylic acid ointment.