New spectrophotometric methods for the determination of sulfadoxine by the formation of Co(II) complexes

New sensitive spectrophotometric methods are developed for the determination of sulfadoxine (SFD). Proposed methods are based on the reaction of drug with aryl aldehyde followed by Co(II) chloride in the acidic medium. The reaction of aryl aldehyde with drug results in the formation of Schiff base which acts as a ligand for the formation of complex with Co(II). Different aryl aldehydes are tested, out of which p-dimethylaminobenzaldehyde (used in method A) and vanillin (used in method B) gave stable green colored complexes. The complexes formed due to p-dimethylaminobenzaldehyde and vanillin are measured at 672 and 665 nm for method A and method B, respectively. The molar absorptivity and Sandell's sensitivity of method A and method B are 0.1264 × 104, 0.2453 and 0.6982 × 104, 0.4444, respectively. The optical reaction condition and their analytical parameters are evaluated. Both the methods are free from interference of the ingredients such as lactose, sucrose and starch, thus it is successfully applied to pharmaceutical formulations.