RESUMO
Objective To establish the HPLC method of assay for diphenhydramine hydrochloride in compound diphenhydramine cream. Method HPLC analysis was carried on ACE5C18S/N-A66766 column (150 mm×4.6 mm, 5 µm) with the mobile phase of methanol-water-triethylamine (70:30:0.67, adjusting pH to 6.50 with phosphoric acid) at room temperature. The detection wavelength was set at 230 nm and the flow rate was 1.0 ml/min. The analyte was extracted from the cream and 20 μl of sample was injected. Results The calibration curve of diphenhydramine hydrochloride was linear in the range of 39.52-197.6 µg/ml (r=0.999 7). The average recovery of diphenhydramine hydrochloride was 100.5% (RSD=1.25%, n=9). The repeatability of the method was expressed using RSD with 0.78% (n=6). The results of assay were 101.3%, 99.83% and 99.62%. Conclusion The method is accurate, sensitive, selective and repeatable, which can be applied for improving the quality standard of compound diphenhydramine cream.