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Determination of Preservatives in Betamethasone Injectable Suspension by HPLC

??OBJECTIVE To establish an HPLC method for determination of the preservatives in betamethasone injectable suspension, including benzyl alcohol, methylparaben and propylparaben. METHODS The determination method was developed with 5 mmol??L^-1 ammonium acetate(containing 1% triethylamine and adjusted to pH 5.0 with glacial acetic acid) as mobile phase A and acetonitrile as mobile phase B, and gradient elution was performed at a flow rate of 1.0 mL??min^-1. The column temperature was maintained at 30 ?? and the detection wavelength was set at 257 nm. RESULTS The resolutions between the three main peaks and adjacent peaks were greater than 1.5. The calibration curves of benzyl alcohol, methylparaben and propylparaben showed good linearity in the ranges of 0.175 9-1.758 6 mg??mL^-1(r=1.000 0), 0.022 3-0.223 1 mg??mL^-1(r=0.999 8), 0.004 35-0.043 47 mg??mL^-1(r=1.000 0), respectively. The average recovery rates were 98.98%, 99.38% and 100.07%, and the RSDs were 0.6%,1.3% and 1.0%(n=9), respectively. The results of test of influencing factors showed that the contents of hydroxyphenylmethyl ester and propylparaben decreased at high temperature. CONCLUSION The developed method is proved by validation to be applicable for the quality control of the preservatives in betamethasone injectable suspension.