Spectrophotometric Determination of Mesalazine in Pharmaceutical Preparations by Diazotization and Coupling with 2,6- Dihydroxytoluene as a New Coupling Agent


A simple and sensitive spectrophotometric method is proposed for the determination of mesalazine (MZ) in some of its pharmaceutical preparations. The method is based on the diazotization of mesalazine by reaction with sodium nitrite in an acidic medium and then coupling of diazonium salt corresponding to mesalazine with 2,6-dihydroxytoluene reagent in basic medium to produce an intense orange colored water-soluble and stable azo-dye for at lest two hrs, and exhibits maximum absorption at 453 nm. Beer’s law is obeyed in the concentration range of 2.5-100 µg of mesalazine in a final volume of 10 ml i.e.,0.25-10.0 ppm with a molar absorptivity of 4.6×104 l. mol-1. cm-1 and sandell sensitivity index of 0.00332 µg. cm-2 . A relative error is -0.48 to -4.80 and relative standard deviation of ±0.01 to ±0.17 depending on the concentration level. The proposed method has been applied successfully to determine mesalazine in pharmaceutical preparations, tablets and suppositories.