Acetylacetone-formaldehyde reagent for the spectrophotometric determination of some sulfa drugs in pure and dosage forms

A new simple and sensitive spectrophotometric procedure for the determination of sulfacetamide sodium (I), sulfadiazine (II), sulfadimidine (III) and sulfathiazole (IV) is based on the reaction of the drug with acetylacetone-formaldehyde reagent to give a yellow product having lambda(max) at 400 nm. Optimization of the reaction conditions has been investigated. A linear correlation was obtained between absorbance at lambda(max) and the concentration. The Beer's law limits of I, II, III and IV are 4-80, 4-72, 4-60 and 4-80 mu g/ml, respectively. For more accurate results, Ringbom optimum concentration ranges were evaluated to be 6-76, 8-66, 6-56 and 8-75 mu g/ml for I, II, III and IV, respectively. The molar absorptivities and Sandell sensitivities for all sulfa drugs under consideration were evaluated. Relative standard deviations of 0.98, 1.07, 0.86 and 0.79\% were obtained for I, II, III and IV, respectively. The method has been compared to the official method and found to be simple, accurate (t-test) and reproducible (F-test). The developed procedures were applied for bulk sulfa drugs and some of their dosage forms without interferences from additive and common prescribed drugs.