Spectrophotometric methods for the determination of nifurtimox in bulk form and pharmaceutical formulations

Three simple and sensitive methods for the assay of Nifurtimox (NIF) which is an active antitrypanocide were developed. These methods are based on the formation of coloured species by treating either its reduction product with 3-methyl-2-benzothiazolinone hydrazone (MBTH) in the presence of ferric chloride (method A) or its hydrolysis product with 2-thiobarbituric acid (TBA) (method B) or by oxidizing it with excess N-bromosuccinamide (NBS) and determining the consumed NBS using p- N-methylaminophenol sulphate (metol)—isonicotinic acid hydrazide (INH) (method C). All variables have been optimized and the reaction mechanisms presented. Regression analysis of Beer's plot showed good correlation in the concentration range of 2.5–10, 2.5–30 and 1.25–7.5 μg/ml for methods A, B and C, respectively. No interference was observed from the additives and the validity of the methods was tested by analysing the tablets. Recoveries were 99.2–100.9%.