Natalia Yu. Stozhko

Ural State University of Economics · Department of Physics and Chemistry

Uric acid is an important component of milk, which has antioxidant properties and protects it from rapid microbiological spoilage. The article studies the change in uric acid content during unwanted spoilage of pasteurized and unpasteurized milk using a developed voltammetric sensor based on a carbon veil. The sensor allows to estimate the content...

The purpose of the study is a comparative analysis and assessment of the current environmental situation against the background of the global environmental crisis and constantly growing turbulence, uncertainty and environmental risks. The article reveals the humanitarian context of modern environmental risks caused by extensive industrial productio...

A potentiometric sensor system (PSS) was developed to assess antioxidant activity (AOA) using the potassium hexacyanoferrates ([Fe(CN) 6 ] 3–/4– ) mediator system. The screen-printed indicator electrode was made of carbon ink modified with multi-walled carbon nanotubes (MWCNTs). The screen-printed silver electrode was potentiostatically modified wi...

Optimization of technological processes using mathematical methods is an integral part of the development of science and technology. This study reports on the application of the Harrington desirability function for multifactorial stability assessment of quasi-reference electrodes (QREs) in a solution with variable content of ferro- and ferricyanide...

This article presents an original planar carbon fiber electrode (PCFE), in which shungite (SHU) is used as a modifier for the first time. Shungite is a unique natural nanostructured composite consisting of carbon in the form of aggregated graphene stacks, oxides of silicon, titanium, aluminum, iron, magnesium, potassium, etc. Macro- and micro-eleme...

Plant phenolic compounds demonstrate bioactive properties in vitro and/or in vivo, which creates demand for their precise determination in life sciences and industry. Measuring the concentration of individual phenolic compounds is a complex task, since approximately 9000 plant phenolic substances have been identified so far. The determination of th...

This paper presents a novel eco-friendly sensing material based on carbon paper (CP) volumetrically modified with a composite nanomodifier that includes functionalized poly(diallyldimethylammonium chloride) graphene (PDDA-G) and phytosynthesized gold nanoparticles (phyto-AuNPs). The functionalization of graphene was justified by Fourier-transform i...

Thermal and non-thermal technologies used in food processing should be not only effective in terms of decontamination and preservation but also minimize undesirable losses of natural bioactive compounds. Arabica (Coffea arabica) is the most cultivated variety of coffee, making it a valuable source of phytonutrients, including antioxidants. In the p...

The paper describes the development of an electrochemical sensor to be used for the determination of synthetic food colorants such as Sunset Yellow FCF (SY) and Tartrazine (TZ). The sensor is a carbon paper (CP) electrode, manufactured by using hot lamination technology and volume modified with fine-grained graphite powder (GrP). The sensor (GrP/CP...

Gold nanoparticles are widely used in electrosensing. The current trend is to phytosynthesize gold nanoparticles (phyto-AuNPs) on the basis of the “green” chemistry approach. Phyto-AuNPs are biologically and catalytically active, stable and biocompatible, which opens up broad perspectives in a variety of applications, including tactile, wearable (b...

A voltammetric carbon fiber sensor for the determination of nitrite ions was developed. The carbon veil was used as a carbon fiber and modified non-ionic surfactant Triton X-100 (TrX100). For the manufacture of the carbon veil electrode (CVE), a simple modern technology of thermal bonding was used, which allows to produce well-reproducible electrod...

Testing as an assessment technique has been widely used at all levels of education—from primary to higher school. The main purpose of the paper is to evaluate the effect of context-based testing in teaching and learning of analytical chemistry in a Russian university. The paper formulates the objectives of context-based testing, discusses its featu...

The paper describes the development of a carbon veil-based electrode (CVE) for determining uric acid (UA) in saliva. The electrode was manufactured by lamination technology, electrochemically activated and used as a highly sensitive voltammetric sensor (CVEact). Potentiostatic polarization of the electrode at 2.0 V in H2SO4 solution resulted in a h...

In contemporary bioanalysis, monitoring the antioxidant activity (AOA) of the human skin is used to assess stresses, nutrition, cosmetics, and certain skin diseases. Non-invasive methods for skin AOA monitoring have certain advantages over invasive methods, namely cost-effectiveness, lower labor intensity, reduced risk of infection, and obtaining r...

Currently, the food industry pays great attention to the research of antioxidants used as food additives and functional food ingredients. Monitoring the antioxidant activity (AOA) of foods containing dietary antioxidants serves as an innovative tool for the food industry development and is an urgent research task. The article presents data on the d...

A film carbon veil-based electrode (FCVE) modified with non-ionic surfactant Triton X-100 (TrX100) has been developed for nitrite determination. A new simple and producible technique of hot lamination (heat sealing) has been used for the FCVE manufacturing. The paper presents the findings of investigating the FCVE and the TrX100/FCVE by using volta...

An original voltammetric sensor (Au-gr/CVE) based on a carbon veil (CV) and phytosynthesized gold nanoparticles (Au-gr) was developed for ascorbic acid (AA) determination. Extract from strawberry leaves was used as source of antioxidants (reducers) for Au-gr phytosynthesis. The sensor was characterized by scanning electron microscopy, energy-disper...

The paper discusses the problem of the sustainable functioning of the educational system in the context of the intensive development of information technologies, which is urgent in Russia and, practically, in other countries throughout the world. It has become especially acute in recent years in connection with the forced transition to a large-scal...

Synthesis of gold nanoparticles (phyto-AuNPs) with the use of leaf extracts (phytosynthesis) is based on the concept of Green Chemistry. The present study is conducted to discuss how antioxidant activity (AOA) of extracts from plant leaves impacts on the kinetics of phytosynthesis, the size of the formed nanoparticles, and the stability of their na...

A new version of the hybrid potentiometric method (HPM) for evaluating the antioxidant activity (AOA) of fruits and vegetables, which we called contact (CHPM), is proposed. A screen-printed electrode pair coated by a membrane impregnated with a mediator serves as a sensor system. The potential shift, which is observed when the sensor system is expo...

Unreliable terminology and incompatible units of antioxidant activity/concentration expression lead to the failure of antioxidant clinical trials, ambiguity of conclusions about the effect of a chosen therapy in medicine and evaluation of food quality, diet, difficulties using information in monitoring the training process in sports, etc. Many diff...

The skin is a natural barrier between the external and internal environment. Its protective functions and the relationship of its state with the state of health of the organism as a whole are very important. It is known that oxidant stress (OS) is a common indicator of health status. This paper describes a new sensory system for monitoring OS of th...

This paper focuses on the development of a simple, fast and reliable technique of sample preparation to be employed as part of potentiometric measurements of plant total antioxidant activity (AOA). Plant extracts and plant microsuspensions were analysed. The conditions for obtaining plant extracts were chosen: they exhibited the highest antioxidant...

The paper presents a new variant of non‐invasive potentiometric method for determination of human skin antioxidant activity (AOA). The use of a porous cellulose acetate membrane as the carrier for reagent solution (potassium hexacyanoferrate (III)) is presented. The increase of reagent shelf life, improvement the reproducibility of the results (dur...

The unique properties of nanoparticles make them an extremely valuable modifying material, being used in electrochemical sensors. The features of nanoparticles affect the kinetics and thermodynamics of electrode processes of both nanoparticles and redox reactions occurring on their surface. The paper describes theoretical background and experimenta...

The unique properties of nanoparticles make them an extremely valuable modifying material, being used in electrochemical sensors. The features of nanoparticles affect the kinetics and thermodynamics of electrode processes of both nanoparticles and redox reactions occurring on their surface. The paper describes theoretical background and experimenta...

Introduction. The aim of the study was the hygienic characteristics of meat treated with high pressure, according to organoleptic and microbiological parameters, the processes of oxidative damage and changes in the chemical composition during storage. Material and methods. For the experiment, a control and experimental group were selected, includin...

The paper discusses the mechanism of uric acid (UA) electrooxidation occurring on the surface of gold nanoparticles. It has been shown that the electrode process is purely electrochemical, uncomplicated with catalytic stages. The nanoeffects observed as the reduction of overvoltage and increased current of UA oxidation have been described. These na...

This article aims to determine the effect of a virtual chemistry laboratory on university student achievement. The article describes a model of a laboratory course that includes a virtual component. This virtual component is viewed as a tool of student pre-lab autonomous learning. It presents electronic resources designed for a virtual laboratory a...

A new sensitive non-invasive gold nanoparticle-based sensor that enables to detect thiols in the human skin has been developed. The detection procedure implied the assessment of the color change of a paper sensor resulting from aggregation of gold nanoparticles caused by thiols. The ratio of the intensity of the photo image blue channel vs the red...

The paper discusses student research project work as an essential component of the context-based approach to teaching analytical chemistry. The key principles of student research project work were formulated. Step-by-step planning and organization of this work was proposed considering different functions of the teacher and the student in the resear...

Physical and mathematical models are proposed which describe the electrochemical transformation of compounds diffusing from the solution to an ensemble of nanoparticles (i.e., nanoelectrodes), located on a solid bulk electrode surface. Electrochemical oxidation of ascorbic acid at solid electrodes (glassy carbon, Graphite Ultra Trace and gold) unmo...

Here is reported the determination of water-soluble antioxidants from human skin by potentiometry and capillary zone electrophoresis. A rapid and simple capillary electrophoretic method was developed for the determination of ascorbic acid, uric acid, and glutathione. The limits of detection were 1.5 µ mol L−1 for uric acid, 4.5 µ mol L−1 for glutat...

The paper aims to show how the context-based approach can be applied to teaching the analytical chemistry course to the university students with major in food processing technology and food expertise. The article describes the principles that underlie the context-based teaching and innovative approaches to structuring analytical chemistry lab work...

Aim. The work is devoted to the study of the conditions of formation in the educational process on the subject «Analytical Chemistry and Physical Methods of Analysis», the most important competences necessary to the modern specialist in the food sector (production and examination of food quality technology) for food quality control and food safety...

The article studies a way of enhancing student cognition by using interdisciplinary project-based learning (IPBL) in a higher education institution. IPBL is a creative pedagogic approach allowing students of one area of specialisation to develop projects for students with different academic profiles. The application of this approach in the Ural Sta...

For the first time, carbon screen-printed electrodes (CSPE) modified with bismuth nanoparticles have been used to determine sulfide ions with stripping voltammetry (SV) by formation of sparingly soluble compounds with the electrode material. The impact of weight, degree of bismuth dispersion on CSPE surface, and Bi2S3 accumulation parameters on the...

The purpose of this paper is to propose mathematical modeling of different kinds of electrochemical processes. Electrooxidation of nitrite ions on some types of electrodes (glassy carbon, screen-printed carbon-containing, gold, and gold nanoparticles) and oxidation of ascorbic acid on gold electrodes nonmodified and modified by gold nanoparticles w...

The article describes the system of computer assisted learning (CAL) designed for classes in analytical chemistry. The system is developed in the Ural State University of Economics (USUE, Yekaterinburg, Russia). The CAL system consists of two subsystems for organizing students' laboratory (in class) work and independent study (outside of class) and...

The article proposes theoretical and experimental justification for using potentiometry as a new noninvasive method of evaluating antioxidant/oxidant state (oxidative stress) of a skin. Since the inductor of oxidative stress is an overall deficit of electrons accessible to cells, electrochemical methods of evaluating this parameter are naturally co...

The article presents the findings of microscopic and electrochemical studies of electrooxidation of bismuth particle of varying sizes. Bismuth particles were immobilized on the surface of indifferent carbon containing screen-printed electrodes. The calculations and experimental studies demonstrated that the transition from macroparticles to nanopar...

Carbon screen-printed electrodes (CSPE) are used as substrate for bismuth nanoparticles immobilization. Sensors modified with bismuth nanoparticles of different origin (prepared by the method of gas condensation and chemically synthesized) are used to determine nickel by adsorptive stripping voltammetry (AdSV). The effect of the structural organiza...

This article presents the findings of microscopic and electrochemical studies of electrooxidation of silver nanoparticles of varying sizes in comparison with “bulk” silver. Silver particles were immobilized on the surface of indifferent carbon-containing screen-printed electrodes. Vacuum-deposited silver represented the “bulk” electrode. The calcul...

The article presents the findings of microscopic and electrochemical studies of size-dependent gold particles electrooxidation. Gold particles were immobilized on the surface of carbon-containing screen-printed electrodes. The experiment demonstrated that the transition from macroparticles to nanoparticles caused a shift of the maximum current pote...

A procedure is developed for the immobilization of bismuth nanoparticles prepared by the method of gas condensation on inert supports manufactured by the screen printing method using carbon-containing inks. The electrochemical behavior of the immobilized bismuth nanoparticles is investigated, and the conditions of their electrochemical activation a...

A correlation between the morphology of the solid surface and electrochemical response was found in microscopic and electrochemical investigations. A shift of the oxidation potentials of metals to more negative values was observed on electrodes with microstructured surface with respect to similar processes on macrostructured electrodes. The formati...

Papers dealing with modified electrodes made of carbon materials and composites for use in stripping voltammetry of metals have been reviewed. The review consists of two parts, of which the first considers applications of modified glassy carbon and carbon paste electrodes, while the second describes diverse modified carbon-containing composite and...

The second part of the review, which covers modified carbon-containing electrodes, describes composite and microelectrodes. Electrodes made of commercial and laboratory carbon-containing composite materials are discussed. Impregnated and thick-film electrodes and microelectrodes made of carbon fibers form a separate group. Various modifiers and met...

The novel bismuth modifying technique for disposable thick film carbon containing sensors (TFCC) by means of a surface synthesis of the modifier (bismuth phosphate) have been developed. The optimal composition and the method of cathodic reduction (“activation”) of the modifying BiPO4 layer has been proposed. These conditions provided the structure...

Selected trace metals (copper, lead, and zinc), an ultra-trace metal (cadmium) and pesticides (metalaxyl, penconazole, procymidone and parathion) were determined during the fermentation step in a vinification process. Two laboratory-scale fermentations were carried out, with and without skins (for the production of red and white wine, respectively)...

Without Abstract

A ceramic composite electrode for the determination of selenium(IV) was manufactured using solgel and screen-printing technologies. This electrode exhibits a higher sensitivity and selectivity in comparison with the other studied carbon-containing electrodes. The effect of the type and amount of graphite powder, modifier, catalyst, and pore-forming...

An original, simple, and rapid method consuming little labor and eliminating the contamination of a sample and the loss of analytes is proposed for the electrochemical preparation of wine samples. The time of electrochemical sample preparation (ECSP) is no longer than 10 min. A four-electrode single-compartment electrolyzer allows all stages of vol...

A thick-film graphite-containing electrode modified with calomel was proposed for determining iron(III) by stripping voltammetry. Of the organic reagents under study, pyrocatechol was found to be the most sensitive in determining iron(III). The detection limit for iron(III) was 3.6 10−10 M (0.02 g/L) at a preconcentration time of 30 s. The analytic...

Papers of Russian authors on the development of thick-film electrodes fabricated by screen-printing technology and their use in inorganic voltammetric analysis are surveyed. Procedures for determining elements are classified by the version of analyte preconcentration on thick-film electrodes of different types. The advantages of new electrodes over...

A mercury-free thick-film graphite-containing electrode modified with formazan is proposed for determining manganese(II) by cathodic stripping voltammetry. The detection limit for manganese(II) found with this electrode is 0.04 g/L at a preconcentration time of 60 s. The analytical signal from manganese(II) is a linear function of its concentration...

Methods of express voltammetry determinations of iron (II) and iron (III) in wine with the help of thick-film graphite-contain electrode and a modified sol-gel electrode are designed. Analysis time is 10-20 minutes. Procedures are tested on white and red wines. The regularity of determination is demonstrated by comparison with other methods.

A mercury-free thick-film graphite electrode is proposed for determining cobalt(II) by stripping voltammetry. It was found that nitroso-R-salt ensures the highest efficiency of the preconcentration and determination of cobalt(II), as compared to the other organic reagents. The effects of different parameters (the pH of the solution, the concentrati...

Electrochemical sensors were developed based on thick-film carbon-containing electrodes coated with thin xerogel films fabricated by the sol–gel technology. The effect of the composition of a hydrolyzed mixture and the types of carbon-containing inks and a support on the properties of sol–gel electrodes was studied. Conditions for preparing sol–gel...

The surface microreliefs and voltage–current characteristics of gold electrodes and modified thick-film graphite-containing electrodes were studied. The relationship between the formation of an analytical signal of mercury(II) and the surface microrelief was determined. It was found that the surface of a modified graphite-containing electrode is a...

A method has been developed for determination of copper, lead, cadmium and zinc concentration in dry wines by stripping voltammetric with a thick-film modified graphite-containing electrode (TFMGE). This method does not require the preliminary acid digestion of the sample or other approaches for the destruction of organic substances. The optimal co...

The tape electrode, consisting of flexible polymer substrate, covered with carbon-containing paste and modified by calomel, has been developed as an alternative to the flexible voltammetric sensor with replaceable surface, which was made of a carbon-containing filament and modified beforehand by insoluble mercury diethyldithiocarbaminate. The tape...

Three types of thick-film graphite-containing electrodes were proposed for determining selenium(IV) by stripping voltammetry. Their advantages over the widely used gold-film, glassy-carbon, and impregnated graphite electrodes were demonstrated. Optimum conditions for determining selenium(IV) were chosen. Procedures for determining selenium(IV) in d...

The electrochemical behavior of some hetarylated formazans introduced into the bulk of carbon-containing inks of thick-film screen-printed electrodes was studied. The compositions of complexes formed at the electrode surface were found, and their stability constants were estimated. It was shown that the modification of a carbon-containing thick-fil...

A mercury-free modified screen-printed electrode was proposed for the preconcentration and determination of Cu(II), Pb(II), Cd(II), and Zn(II). The simplicity of design, compactness, and low cost of the developed electrode; the possibility of using it as a disposable electrode; and no need in any operations on the mechanical treatment of the electr...

An electrochemical sensor, namely, a graphite thick-film electrode modified with Au(III) was proposed for the determination of Hg, As, Se, and Cu. The detection limits for mercury and arsenic using the new sensor are 0.005 and 0.1 g/L, respectively.

The review covers over 230 papers published mostly in the last 5 years. The goal of the review is to attract the attention of researchers and users to stripping voltammetry in particular, its application in environmental monitoring and analysis of foodstuffs. The sensors employed are impregnated graphite, carbon paste, thick film carbon/graphite an...

The paper describes the determination of mercury (II) by anodic stripping voltammetry (ASV) using modified disposable thick film graphite electrodes (MDTFGEs).The optimized conditions, interferences, and analytical applications of mercury determination using thick film electrodes modified with a gold (III)/pyrrolidinedithiocarbamate (PDC) complex a...

Various types of modified thick-film graphite electrodes are reviewed. Two modification options are available: either in situ modified or beforehand. Electrodes modified in situ by various organic compounds were used for the determination of W, Mo, Cr, Ni and Mn by adsorptive stripping voltammetry. Insoluble inorganic salts, insoluble organic compl...

The paper describes the development of modified thick film graphite electrodes (TFGEs) for the stripping voltammetric determination of mercury. It is well known that mercury is determined best using gold electrodes. Therefore we have decided to modify the surface of a solid graphite containing electrode so that after the preliminary chemical or ele...

The paper describes the determination of tin by ASV using modified thick film electrodes. Three different types of electrodes were developed: One modified with a mixture of Nafion and mercury(II)acetate, one modified with diethyldithiocarbamate (DDC) or pyrrolidinedithiocarbamate (PDC) and mercury(II)acetate, and one modified with calomel. The anal...

The application of three types of in situ modified electrode in stripping voltammetry is considered. Electrodes of type I were obtained by surface modification using triphenylmethane dyes and were used for the determination of the concentrations of SbIII and l– ions. Electrodes of type II were modified by electrodeposition of mercury on a graphite...

This paper presents an electrochemical method of destroying organics in solutions and to separate electropositive elements. The authors studied the effect of electrochemical wet ashing on the determination of Cu, Pb, Cd, and As in waters with low and high organic carbon contents. The solutions were prepared with water triple distilled from an alkal...