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We studied the effect of the mutual arrangement of substituents in an aminobenzoic acid molecule on the analytical characteristics of the determination of bacteria Staphylococcus aureus using a label-free electrochemical immunosensor. An immunosensor based on m-aminobenzoic acid demonstrated the best performance. This is apparently due to the best combination of the density of the coating formed by electrochemical deposition and the availability of carboxyl functional groups for carbodiimide cross-linking with an immunoreceptor.

The new Russian drug Triazid® is a highly effective antiviral agent. The active substance of the drug (5-methyl-6-nitro-7-oxo-4,7-dihydro-1,2,4-triazolo[1,5-a] pyrimidinide l-arginine monohydrate, triazid) belongs to azoloazine series compounds. Using cyclic voltammetry, it was found that the electrochemical activity of triazid (TD) in Britton–Robinson aqueous buffer solutions (BRB) on a glassy carbon electrode is due to the electroreduction of the nitro group bound with the conjugated aromatic system. The maximum current of triazid reduction in the potential range 0.0‒(‒1.25) V was used as an analytical signal. A method was developed for the quantitative determination of triazid by direct cathodic square-wave voltammetry. The linearity range of the calibration graph using the developed method in a BRB solution (pH 4) is 10–500 mg/L (R2 = 0.9998) with the limit of detection for TD 1.9 mg/L. The developed method was used to analyze the Triazid pharmaceutical substance for the concentration of TD. The results obtained satisfy the stated requirements of the draft pharmacopoeial article of the company “TRIAZID substance” for the content of TD found by HPLC.

We present the results of synthesis and study of the electrocatalytic activity of gold and silver nanoparticles of different composition (individual metals, core–shell particles, nanoalloys, and particles synthesized electrochemically), immobilized on the surface of a glassy carbon electrode, with respect to cholesterol. A surfactant (cetyltrimethylammonium bromide) is selected to create an aqueous–organic emulsion of cholesterol. It is demonstrated that nanoparticles with a gold core and a silver shell with the regression equation of I = 1.4 × 10–5 c chol + 5.8 × 10–5 (R 2 = 0.97) and silver nanoparticles synthesized electrochemically with the regression equation of I = 1.0 × 10–5 c chol + 3.0 × 10–4 (R 2 = 0.95) possess optimal electrocatalytic characteristics.

Reaction of quinoxaline or its 6,7-difluoroderivative with C-nucleophiles in nitrogen atmosphere afforded along with the products of hydrogen substitution in the heterocyclic ring the corresponding bisquinoxalines. An ESR signal of the cation-radical of the diprotic salt of quinoxaline was detected in the DMSO solution of quinoxaline and dimedone.

An electrochemical immunoassay method is developed for determining the strain of Escherichia coli ATCC 25922 with the use of electroactive nanocomposite particles based on magnetite Fe3O4 coated by SiO2 modified with ferrocene as a signal label. A sensitive, direct, and easily measured analytical response is obtained by cyclic voltammetry. The developed method enables the determination of bacterial cells at a minimum concentration of 2.3 × 103 CFU/mL. The analytical range is 2.3 × 103–2.3 × 107 CFU/mL; the detection limit is 2.5 × 102 CFU/mL. The required sample volume is 0.5 mL, and the analysis time is 40 min.

Methods are developed for the non-enzymatic chronoamperometric determination of urea in blood serum and creatinine in model solutions imitating the composition of blood serum. The selectivity of determination is ensured using columns packed with an anion-exchange resin for urea or synthesized molecularly imprinted polymers for creatinine.