Raboshvil K. New analytical forms for the spectrophotometric determination of vanadium (V) and selenium (VI) based on their complexes with 4-sulfo-2 (4'-sulfonaphthalene-1'-azo)naphthol-1

The paper is devoted to the study of the peculiarities of the oxidative behavior of the сarmoazine (KAN) azo dye and its interaction with metal ions in higher degrees of oxidation, on the basis of which new analytical forms for selective spectrophotometric determination of V (V) and Se (VI) in complex objects of various origin were proposed. The method of cyclic voltammetry has shown that oxidation and reduction peaks at 0.935 V and 0.170 V, respectively, are observed for KAN, and currents have an adsorption nature. Chemical-analytical characteristics of the complexes in water-ethanol solutions were determined: V (V): KAN = 1: 3, (pHopt 0, λmax = 365 nm, εmax = 1.6·104, Kst≈109, charge of the complex (-6) , C min = 0.26 mg / ml) Se (VI):KAN = 1: 4 (pHopt -0.5, λmax = 370 nm, εmax = 1.0·104, Kst = 4.6·103, charge of the complex (-8), Cmin = 1.58 μg/ml) and a mechanism for their formation was proposed. The probable structure of complete compounds after the redox interaction with KAN was proposed and the effect of the presence of oxygen atoms in the composition of the complex metal-metal ion on the kinetics of the reaction is shown. The activating action of the Mn (VII) ions on the complexing ability of the ions V (V), Se (VI) and Cr (VI) with KAN has been revealed, which allows them to be determined at room temperature. Based on the complex compounds of vanadium (V) and selenium (VI) with KAN, a new analytical form is proposed, a complex of simple and express spectrophotometric techniques has been developed, which has been tested in their determination in some food products of vegetable origin, medicinal herbs and multivitamin complex. It was shown that the use of the KAN allows the determination of vanadium (V) (0.26÷1.79 μg/ml) and selenium (VI) (1.58÷12.64 μg/ml) in the presence of ions forming macro- and microstructure of analyzed objects.