Simple, sensitive and accurate spectrophotometric methods have been developed for the determination of Sulphamethoxazole (SMZ) drug . This method based on the reaction of Sulphamethoxazole (SMZ) with new organic reagent (BYN) it was prepare by reaction between ethyl acetoacetate with 2,4-Dinitrophenylhydrazine. The azo dye product shows absorption maximum at 435 nm. The linearity ranges of Sulphamethoxazole are (2-14 μg.mL-1) with molar absorptivity (14412.77 L.mol-1.cm-1), Sandell's sensitivity index (0.0175 μg.cm-2) , detection limit and Quantification limit ( 0.057, 0.175 μg / ml) respectively. The results showed there are no interferences of excipients on the determination of the drug. The proposed method has been successfully applied for the determination of sulfanilamide in pure and pharmaceutical formulations.

Development of an easy, inexpensive, fast and selective spectrophotometric method for the determination of Folic Acid  (FA) by its reaction with 4-nitro aniline reagent, with good sensitivity, as an oxidative coupling method in the presence of Potassium permanganate solution, and it was found that the concentrations that were agreement with Beer-Lambert’s law at the wavelength of 374 nm ranged between 1- 21 µg/ml of folic acid solution, and a deviation from Beer’s law occurs at a concentration higher than 21 µg/mL, gave a linear coefficient and correlation coefficient its value is 0.9994, 0.9996, respectively, While the value of the molar absorption coefficient  12138.5 L/mol.cm and Sandel's sensitivity  0.0363 gm/cm2  with  the limits of qualitative and quantitative detection 0.103 and 0.363 μg / ml-1, respectively. The proposed method was successfully applied for the determination of folic acid in its pharmaceutical preparations, from Erbil Company – Iraq. Trade name (folic acide).