Selective Extraction Spectrophotometric Determination of Iron by Utilizing the Peculiar Absorption of Iron(II)–2-(2-Thiazolylazo)-5-dimethylaminophenol Complex

Abstract

Abstract Thiazolylazo compounds react with iron(II) to form brownish complexes, which show a characteristic absorption in near-infrared region. These compounds possess the hydroxyl group in the o-position next to the azo group. Among them, iron(II)-2-(2-thiazolylazo)-5-dimethylaminophenol complex has the absorption maximum at 760 nm in chloroform; the optimum pH for iron extraction lies between 8.2–10.0. Beer’s law holds up to 2.0 μg cm−3 of iron and the molar absorption coefficient is 2.70×104 dm3 mol−1 cm1. The composition and the extraction constant of the complex are estimated to be Fe: TAM=1 : 2 and logKex=−4.20±0.04, respectively. Since the present method utilizes the specific absorption of the iron(II)-TAM complex, the presence of many ions is tolerable, especially of 3d type metals. The method was applied to the determination of traces of iron dissolved in river and sea waters with satisfactory results.