Abstract.
A simple and rapid flow-injection (FI) method is reported for the simultaneous spectrophotometric determination of Fe(II) and Fe(III) in pharmaceutical products. The method is based on the reaction of Fe(II) with 2,2′-dipyridyl-2-pyridylhydrazone (DPPH) in acidic medium to form a water-soluble reddish complex (λ max=535 nm). Fe(III) reacts with DPPH under flow conditions only after its on-line reduction by ascorbic acid (AsA). Both analytes were determined in the same run via a double-injection valve, which enabled the simultaneous injection of two sample volumes in the same carrier stream ("single-line double-injection" approach). The two well-defined peaks produced corresponded to total iron [Fe(II)+Fe(III)] and Fe(II). Speciation of the analytes in their mixtures was achieved by multiple regression analysis. The calibration curves obtained were linear over the ranges 0–30 and 0–50 mg L–1 for Fe(II) and Fe(III), respectively, and the precision [s r=1.0% for Fe(II) and 1.5% for Fe(III)] was satisfactory. The method proved to be selective and adequately sensitive (c L=0.25 and 0.17 mg L–1 for Fe(III) and Fe(II), respectively, in mixtures). Application of the method to the analysis of pharmaceutical samples resulted in excellent accuracy; the percent mean recoveries were in the range 99.0–102.0% for both Fe(II) and Fe(III) and the mean relative error was e r=1.0%.
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Themelis, D.G., Tzanavaras, P.D., Kika, F.S. et al. Flow-injection manifold for the simultaneous spectrophotometric determination of Fe(II) and Fe(III) using 2,2′-dipyridyl-2-pyridylhydrazone and a single-line double injection approach. Fresenius J Anal Chem 371, 364–368 (2001). https://doi.org/10.1007/s002160100930
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DOI: https://doi.org/10.1007/s002160100930