Spectrophotometric Determination of Sulfasalazine by Coupling with Diazotized p-Nitroaniline - Application to Pharmaceutical Formulations

A simple spectrophotometric method for the determination of sulfasalazine has been developed. The method is based on the coupling reaction of sulfasalazine in basic medium with diazotized p-nitroaniline, to form a yellow orange water soluble azo dye that shows maximum absorption at 452 nm. Beer's law is obeyed over the concentration range 5-700 g of sulfasalazine in a final volume of 25 ml, i.e, (0.2-28 ppm) with a molar absorptivity of 2.88104 1.mol-1.cm-1 and Sandell's sensitivity index of 0.0138 g. cm-2, a relative error of 0.99 to 1.0 % and a relative standard deviation of 0.03 to 1.09% depending on the concentration level. The proposed method has been applied to assay of sulfasalazine in pharmaceutical formulations (tablets).