Abstract
2-(2-Thiazolylazo)-4-methoxyphenol (TAMP) forms a brownish 2:1 complex with iron(II) in the presence of ascorbic acid; the complex has a characteristic absorption at 784nm in chloroform. By utilizing this peculiar absorption, selective spectrophotometric determination of iron has been developed. The optimum pH for iron extraction lies between 5.0-9.3 and Beer′s law holds up to 5.0μg/ml of iron. Many type of ions are tolerable. The method was successfully applied to the determination of iron in river waters. The extraction constant of iron(II) complex was logKex=-2.50±0.12 and the extraction mechanism was kinetically investigated. The complexation rate was first-order with respect to iron(II) and TAMP concentrations and independent of ascorbic acid concentration. From these results, the major extraction rate-determining step was concluded to be a 1:1 complexation reaction between iron(II) and dissociated TAMP. Kinetic data and activation parameters for the first-order reaction were determined and discussed.
