Spectrophotometric Determination of Sulfadiazine via Diazotization and Coupling Reaction - Application to Pharmaceutical Preparations

A simple, rapid, accurate and sensitive spectrophotometric method has been developed for the quantitative determination of sulfadiazine (SDz) in both pure and its dosage forms. The method is based on diazotization of primary amine group of sulfadiazine with sodium nitrite and hydrochloric acid followed by coupling with γ-resorsolic acid (2,6dihydroxybenzoic acid) in alkaline medium of sodium hydroxide to form a yellow coloured azo dye shows a maximum absorption at 458 nm against reagent blank solution. Beer's law is obeyed over the concentration range of 10-300 µg of SDz / 25 ml (0.4-12 ppm) with a determination coefficient (R 2 =0.9998 ) and molar absorptivity 4.38×10 4 l.mol -1 .cm -1 and a relative error in the range of 0.1- 0.64% and a relative standard deviation from ± 0.27 to ± 1.21 % depending on the concentration level of SDz. The method is suitable for the determination of sulfadiazine in the presence of other ingredients that are usually present in dosage forms. The effect of organic solvents on the spectrophotometric properties of the azo dye and the composition of the resulting product have also been worked out and it is found to be 1:2 γ-resorsolic acid: sulfadiazine. The method has been successfully applied to the determination of sulfadiazine in its pharmaceutical preparations ( tablet, and burn cream ).