The main methods of quantitative determination of silicon compounds in natural water and its forms of existence were considered. Recommendations are offered on a choice of the method for determination of silicon compounds concentration in natural waters depending on the pH and types of waters. It was established that it is necessary to use the method of atomic absorption spectrometry for fresh neutral waters and both methods of spectrophotometric and atomic absorption spectrometry for alkaline and brackish and salty waters.

In this paper some basic data from the published sources concerning determination of selenium by anodic and cathodic stripping voltammetry in various matrices are presented. The key results regarding the choice of analytical conditions for the selenium voltammetric determination are also reported. Besides, the article describes the developed procedures for selenium quantitative determination in food and various biological objects. The voltammetric methods of selenium definition techniques have been developed and their certification by metrological service of Tomsk polytechnical university was carried out. The data o the certified techniques have been included in the Information fund of the measurement techniques applied in the spheres of state regulation of maintenance of unity of measurements in the Russian Federation, and a part of them - to the Register of the techniques accepted to use in the Republic of Kazakhstan.

The study demonstrates the use of various nanomaterials (carbon materials, organic materials, nanocomposites, metals and metal oxides) for the electrodes in the voltammetric determination of drugs. The article presents the findings of the research aimed at increasing the number of identified organic compounds and pharmaceuticals using electrodes made of nanomaterials.

The method of potentiometric titration with a copper electrode is used for the determination of the total acidity and concentration of citric acid (CA) in identifying the adulteration of wines. The procedure is suitable for the determination of citric acid in wines in the range from 0.1 to 3.5 g/L in the presence of 30-fold amounts of tartaric, acetic, malic, succinic acids and a 10-fold amount of oxalic acid after the separation of organic carboxylic acids on an AV-17-8 anion exchanger. The procedure was developed and certified for the potentiometric determination of the mass fraction of citric acid in table wines and wine materials with an error not exceeding 20%. The criteria (mass fraction of citric acid, the percentage of citric acid in the total acidity, and the shape of the curves of potentiometric titration) were proposed for revealing the adulteration of the acid composition of wines.

Systematic inaccuracy of analytical signal of the determined component has been theoretically estimated using the equations taking into account the influence of electrochemical system resistance and conditions of its recording in the method of inverse voltamperometry. The obtained results of calculation are taken into account at selection of voltamperometry analysis optimal conditions of

It was shown that anodic voltammetry at graphite electrodes can be used for determining thiourea in solutions of copper refinery electrolytes. The proposed procedure involves dilution, the addition of hydrogen hydroxide, and the ultrasonic treatment of the resulting solution to eliminate the matrix effect.

A new procedure for the voltammetric determination of toxic (As, Cd, Pb) and essential (Se, Cu, Zn, Fe) elements in various biologically active additives (BAAs) based on phytopreparations has been developed. Sample preparation includes the acid (HNO 3 + H 2 O 2 ) or UV destruction of interfering substances followed by the reduction of As(V) and Se(VI) to the corresponding electroactive As(III) and Se (IV) forms. The elements Zn, Cd, Pb, and Cu are simultaneously determined using a mercury film electrode; As and Fe are determined consequently, and Se is analyzed separately using a gold/graphite electrode and an appropriate supporting electrolyte. The content of elements in various analyzed BAAs varied in a broad range of concentrations (mg/kg): Zn, 0.3 - 1000; Pb, 0.001 - 0.5; Cu, 0.1 - 200; As, 0.01 - 1.0; Fe, 20 - 2000; and Se, 0.1 - 50. Metrological attestation performed with a large number of samples (above 400) showed a repeatability of 9 %, a reproducibility of 13%, and an accuracy of 30%. The proposed analytical procedure is included into the Federal List of Methods issued by the State Standard Pharmacological Committee of the Russian Federation, which involves methods admitted for use in the field of State Metrological Control and Supervision, and is recommended for use in laboratories of BAA producing plants, state sanitary-epidemiological supervision offices, etc.

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.

A new procedure for the voltammetric determination of toxic (As, Cd, Pb) and essential (Se, Cu, Zn, Fe) elements in various biologically active food additives (FAs) based on phytopreparations has been developed. Sample preparation includes the acid (HNO3 + H2O2) or UV destruction of interfering substances followed by the reduction of As(V) and Se(VI) to the corresponding electroactive As(III) and Se (IV) forms. The elements Zn, Cd, Pb, and Cu are simultaneously determined using a mercury film electrode; As and Fe are determined sequentially, and Se is analyzed separately using a gold/graphite electrode and an appropriate supporting electrolyte. The content of elements in various analyzed FAs varied in a broad range of concentrations (mg/kg): Zn, 0.3–10000; Cd, 0.001–0.5; Pb, 0.001–0.5; Cu, 0.1–200; As, 0.01–1.0; Fe, 20–2000; and Se, 0.1–50. Metrological attestation performed with a large number of samples (above 400) showed a repeatability of 9%, a reproducibility of 13%, and an accuracy of 30%. The proposed analytical procedure is included into the Federal Register of Methods issued by the State Standard Pharmacological Committee of the Russian Federation, which includes methods admitted for use in the field of State Metrological Control and Supervision, and is recommended for use in laboratories of FA producing plants, state sanitary-epidemiological supervision offices, etc.

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

A simple voltammetric method for quantitative determination of total selenium in various waters in the concentration range of 0.003 - 0.05 mg/liter is described; the method involves a photochemical sample preparation and allows measurements to be carried out with a rated accuracy of 45 rel.%. A distinctive feature of the method is the use of a gold-graphite electrode rather than a mercury electrode and the elimination of interfering anions (chloride, bromide, iodide, nitrate, and others) by replacing the supporting electrolyte at the stage of anodic dissolution of the selenium concentrate. Metrological certification of the method is carried out using the analysis results for waters of 16 types (potable, mineral, river, underground waters, and treated water effluents).

More than 40 methods have been developed and certified for quantitative chemical analysis QCA of food products, environmental specimens, and consumer goods in an accredited laboratory at Tomsk Polytechnical University. Values have also been established for the measurement errors and standards for monitoring the accuracy of these QCA methods.

A sensitive method for determination of arsenic in alcoholic and soft drinks is described that does not require separation or concentration of arsenic and permits monitoring it at the level of 0.02 mg/kg using advanced voltammetric instrumentation.

A rapid procedure for determining tin and lead in juices and canned fruit has been developed. The performance characteristics of the procedure meet the requirements for the procedures of foodstuff analysis. The procedure does not require wet or dry incineration and is suitable for operation in automatic mode.