The electrochemical behavior of vitamin B2 at a glassy-carbon electrode is studied. Some physicochemical parameters of the electrode reaction (pK values for different forms of vitamin B2 and the number of electrons involved in the electrode process) are calculated. A rapid procedure is developed for the quantitative chemical determination of vitamin B2 in breast milk by differential voltammetry.

Potentials of the reduction of gamma-pyrilocyanines, their heteroanalogues, and flavilium dyes on a mercury film electrode and potentials of their oxidation on a glassy-carbon electrode in nonaqueous media are obtained for the first time ever by a voltammetry method. It is shown that the oxidation and reduction potentials depend on the dye molecule structure, in particular, on the nature of the heteroatom in the heterocycle. It is established that the ClO 4 − anion and complex anions InCl 4 − and TlCl 4 − , which enter the composition of cationic flavilium dyes, undergo neither reduction nor oxidation in the potential region studied.

The conditions are found for the voltammetric determination of fat-soluble vitamin E (α-tocopherol acetate) in nonaqueous media using carbon electrodes of different types. The electrochemical behavior of vitamin E is studied, and some parameters of the electrode reaction that are of analytical importance are estimated. The stage of sample preparation is optimized by the multifactorial design of experiments. Procedures for determining vitamin E in multicomponent vitaminized mixtures by differential voltammetry are developed and metrologically certified.

Conditions were selected for the voltammetric determination of streptomycin and azitromycin using electrodes of different types. The interfering effects of cations. anions, and organic substances, food proteins among them, on the analytical signals from antibiotics were estimated. Procedures for determining streptomycin and azitromycin in pharmaceuticals and for determining streptomycin in milk at nano levels were developed.

Rapid voltammetric procedures for the determination of water-soluble vitamins C, B1, and B2, fat-soluble vitamin E (α-tocopherol acetate), and quercetin in bioactive food additives have been developed. The systematic error (i.e., correctness) of the proposed procedures was evaluated using certified reference materials and the additive recovery tests, which gave the following limiting metrological characteristics: relative error, 25 %; reproducibility, 28 %; convergence, 22 %. The full analysis time (with sample preparation) did not exceed 2 hours. Voltammetric determinations under optimum conditions can be performed in the automated regime controlled by a computer according to the specially developed software.

The express voltammetric procedures of the determination of the water-soluble vitamins C, B 1 , B 2 , fat-soluble vitamin E (α-tocopherol acetate) and quercetin in bioactive additives have been developed. The systematic error component was evaluted with using certified reference materials and by recovery tests. The full analysis time (with probe treatment) did not exceed 2 hours. Voltammetric determinations in optimal conditions were computerized and the appropriate software have been designed.

The introduction of foodstuffs, biologically active additives, animal feeds certification procedure requires development of express, high sensitive and accurate methods of determination of a number of chemical organic compounds. Vitamins and some flavonoids belong to alimentary organic substances required in small amounts. The antibiotics contained in foods and biologically active additives based on milk stuffs render toxic activity on human organism. One should pay attention on the high level of contaminating by chloramphenicol, streptomycin, tetracycline -the antibiotics with dangerous side - effects. The optimal conditions of quantitative chemical analysis antibiotics mentioned above, water- and liposoluble vitamins in foodstuffs and feeds, pharmaceuticals (powders, eye drops, tablets etc.) have been determined. The stage of preliminary isolation of determined substances at pretreatment before voltammetric measurements has been considerable simplified. The interference of water-soluble proteins has been eliminated by their hydrolysis, saponification and salting-out with organic solvents and salts. The designed methods allow to control the content of antibiotics, vitamins at levels of the demanded by the normative documents. The methods are certificated

Conditions for determining vitamin B2by stripping voltammetry were found, and a procedure was developed for measuring the mass concentration of vitamin B2in vitaminized supplements and feeds. Random error, as estimated for 13 different samples, varies in the range between 8 and 18 rel %. Total error was 35% in the whole analytical range. The procedure can be used for determining vitamin B2in multivitamin preparations, biologically active supplements, and pharmaceuticals.

Voltammetric methods for quantitative chemical determination of phenol and aniline and their derivatives in natural waters, potable water, and treated waste effluents were studied. For improving the detection limits for phenol and aniline, solid-phase pre-extraction using Styrosorb-type sorbents can be used. Metrological characteristics of the methods are given. The lower limits of analyte concentrations are 0.0004 mg/dm(3) for phenol and 0.00005 mg/dm(3) for aniline. The time of a single determination does not exceed 1.5 h.