Direct spectrophotometric determination of diacerhein in capsules

A simple, rapid and precise ultraviolet spectrophotometric method using 0.1 N sodium hydroxide has been developed and validated for the assay of diacerhein. The drug can be estimated at 277 nm (ultraviolet region, UV) as well as at 502 nm (visible region, VIS). The absorbances were linearly correlated with concentration in the 6.0-24 microg mL(-1) range (r = 0.9999) and 10-34 microg mL(-1) range (r = 0.9998), respectively at 277 and at 502 nm. The relative standard deviation values for intra (n = 6) and inter-day (n = 3) precision were <2%. Recoveries ranged between 99.0 and 101.7%. The method has been successfully applied to the drug assay in capsules. It was also found that the excipients in the commercial capsules did not interfere with the method. Statistical analysis showed no significant difference between the results obtained at two wavelengths (277 nm or 502 nm).