Three simple spectrophotometric methods for the determination of sulphinpyrazone

Three simple and sensitive spectrophotometric methods for the determination of sulphinpyrazone (SP) in bulk samples and pharmaceutical formulations are described. They are based on the oxidation of sulphinpyrazone with excess N-bromosuccinimide (NBS) and determination of the unconsumed NBS with metol-isonicotinic acid hydrazide (method A, lambda(max): 620 nm); by the reduction of Folin-Ciocalteu reagent (method B, lambda(max) 770 nm); or by the formation of a chloroform-soluble, coloured ion-association complex between the drug and Methylene Violet (MV) at pH 7.0 (method C, lambda(max) 545 nm).