Indirect Spectrophotometric Determination of Mesalazine via Chromate-1,5-Diphenyl carbazide Complex

A simple and rapid indirect spectrophotometric method for the determination of mesalazine is developed. The method is based on the rapid reduction of known large amount of chromate CrO4-2 in the presence of mesalazine in acidic medium of 2N H2SO4. The excess amount of chromate is measured after it's reaction with 1,5-diphenylcarbazide which finally gives a pink-violet, water soluble and stable complex, which exhibit a maximum absorption at 546 nm. Beer's law is obeyed in the concentration range from (5-900) g of mesalazine in a final volume of 25 ml (0.2-36 ppm) with a molar absorbtivity of 1105 l.mol-1.cm-1, Sandell's sensitivity index of 0.0015 g .cm-2 and relative standard deviation 0.0848 to 0.3155 depending on the concentration level. The proposed method is applied successfully to the assay of mesalazine in its pharmaceutical prepearation (capsules).