ABSTRACT
<p><b>OBJECTIVE</b>To establish RP-HPLC method for determination of atropine sulphate, diphenhydramine hydrochloride, capsaicin and dihydrocapsaicin in pain-relieving plaster for arthritis.</p><p><b>METHOD</b>The sample were separated on an Alltima C18 Column (4.6 mm x 250 mm, 5 microm) with the moblie phase of CH3 CN-0.1% H3 PO4. Flow rate was 1 mL x min(-1). The detective wavelength was set at 210 and 280 nm. Column temperature was 30 degrees C.</p><p><b>RESULT</b>The calibration curve for atropine sulphate, diphenhydramine hydrochloride, capsaicin and dihydrocapsaicin revealed linearity in the range of 2.01-50.25, 15.08-377.00, 5.02-125.50, 5.03-125.75 mg x L(-1), respectively. The recoveries of atropine sulphate, diphenhydramine hydrochloride, capsaicin and dihydrocapsaicin were 99.00% with RSD of 0.95%, 99.89% with RSD of 1.2%, 100.1% with RSD of 1.5% and 99.51%, with RSD of 1.4%, respectively.</p><p><b>CONCLUSION</b>The method is simple, rapid and accurate, which is suitable for the quality control of pain-relieving plaster for arthritis.</p>