Development of Spectrophotometric Method to Assay Sulfadiazine in Pure and in Pharmaceutical Dosage form through Diazotization and Coupling Reaction

This study involves the development of a sensitive accurate and low-cost spectrophotometric procedure to analyze sulfadiazine as pure and in its dosage forms. In this method sulfadiazine was diazotized with an equimolar solution of sodium nitrite in the presence of hydrochloric acid to form corresponding diazonium salt followed by coupling with phloroglucinol reagent in basic solution of NaOH to produce a yellow water-soluble azo dye that has maximum absorption at 417 nm versus reagent blank. Under optimum conditions. The linearity of the method obeyed Beer’s law in the concentration range 0.25-15 μg/ml with an excellent determination coefficient (R 2 = 0.9992) and molar absorptivity 3.81×10 4 l/mol.cm. The detection limit (LOD) and quantification limit (LOQ) have also been estimated and their values were found to be 0.192 and 0.563 μg/ml, respectively. A relative error% was calculated and found in the range -2.75% to 4.02%, while the precision (RSD%) was estimated as ≤ 1.36%. The stoichiometry of the resulting azo dye was found to be 1:1 sulfadiazine: with stability constant 0.37×10 7 l/mol. The suggested procedure was applied to the analysis of sulfadiazine in cream and veterinary drugs (powder and injection).