A procedure for manufacturing an indicator carbon-paste electrode of ergonomic design and testing of the electrode for voltammetric determination of a number of substances of inorganic and organic origin are described. This electrode is made of a high purity graphite rod (∅6 mm, L = 70 mm) coated with insulation and having a cavity filled with electroactive carbon-containing material at the end of the rod. The characteristic features of the proposed electrode — the insulating body shell made of heat-shrink tube and electrolytic coating of the cavity surface with a conductive metal film — can simplify the design of the electrode and improve the mechanical strength, extend the life of the electrode, and provide the possibility of volumetric and surface modifications with sparing application of the modifying reagents. The performance and metrological characteristics of the new indicator carbon paste electrode were evaluated in testing food, beverages, natural objects for heavy metal ions and pharmaceuticals for hydrogen peroxide and riboflavin (vitamin B₂) using various options: cyclic voltammetry with a linear sweep, square pulse, differential pulse, and inverse voltammetry. When using the developed electrode modified with a bismuth film for determination of cadmium and lead ions, the linear dynamic range of the calibration characteristic was 10 – 110 and 10 – 160 μg/dm³, respectively. The linear dynamic range of the calibration characteristic for riboflavin determination was 0.01 – 0.2 mmol/liter (3.76 – 75.3 mg/liter) for electrode volume-modified with the microparticles of manganese dioxide. The same electrode, modified with MnO₂ nanoparticles obtained during reduction of Mn (VII) ions by Mn (II) ions in a neutral medium was used in chrono-amperometric determination of hydrogen peroxide in model and pharmaceutical preparations with a detection limit 0.03 mmol/liter for H₂O₂. The simplicity of manufacturing the developed indicator carbon-paste electrode, high performance, and cost-effectiveness when using expensive and scarce modifiers, allows us to recommend it to be used in voltammetric analysis and design of various biosensor systems.

Determination of proteins in biological fluids is rather important for diagnostics in current clinical practice. The results of total protein determination depend on the amino-acid composition of the proteins present in the biological fluid. We discuss some aspects of the spectrophotometric determination of proteins in biological fluids, in particular, the methodological features of the technique based on the reaction of proteins with brompyrogallol red (BPGR). The most important advantage of BPGR in the determination of proteins in biological fluids is rather high and equal sensitivity of the dye to the proteins of albumin and globulin fractions, thus minimizing the errors attributed to the mismatch of the protein composition of the analyzed samples and calibration solutions used. The goal of the work is to study the impact of conditions and shelf life of the BPGR solution on the analytical properties of the solution in the spectrophotometric determination of proteins in biological fluids. Stability of the optical and analytical properties of BPGR solutions are studied using Fisher and Student criteria under conditions of different storage temperatures and nature of the stabilizer (ethanol or sodium benzoate) in the reagent solutions. Verification of the correctness of the total protein determination by the proposed method was carried out in spike tests. The introduced additives of standard solutions are prepared from the «Total protein» or «Albumin» calibrators. The developed method of the spectrophotometric determination of the mass concentration of proteins in the urine by the reaction with bromopyrogallol red was tested on real objects, metrologically certified and listed in the Federal register of certified measurement techniques. Analytical and metrological studies have shown that the developed method of protein determination with a reagent based on BPGR provides equal and high sensitivity of determination of albumin and globulin protein fractions in human biological fluids. To increase the shelf life of the reagent solution and preserve the analytical properties of the solution, we recommend to use ethanol as a stabilizer.

The results of spectrophotometric study of the system Re (VII) – HNO₃ – HCl – mercaptoacetic acid – Sn (II) are used to develop a sensitive and selective method of photocolorimetric determination of rhenium in acid nitrate-sulfate solutions formed upon decomposition of molybdenite concentrates with nitric acid and also to reveal trends in complexation of aliovalent rhenium with organic sulfur ligands. Ammonium perrhenate (AR-0) was purified on a Purolite C-100 cation exchanger. Solutions of mercaptoacetic (thioglycolic) acid were prepared from chemically pure Apolda chemical (Germany). Light absorption spectra were recorded on EPS-3T (Hitachi, Japan) and Specord M-40 (Carl Zeiss Jena, Germany) spectrophotometers; the optical density of the solutions was recorded on a KFK-2 (Russia) photocolorimeter. Optimal conditions for the formation of a colored complex compound with mercaptoacetic acid in a mixed hydrochloric-nitric acid solution were determined along with the composition and stability of the complex. The mechanism of redox reactions that occur during complexation is proposed. A technique for monitoring the rhenium content in the products of hydrometallurgical processing of molybdenite concentrates is developed. The procedure provides rhenium determination in the presence of accompanying elements (Mo, Cu, Fe, Ni, etc.) and oxidizing agents (>120 g/liter The developed procedure includes preliminary separation of molybdenum and other interfering impurities by selective sorption of ions on a strongly basic anionite (ChFO) followed by their desorption with a 5 M HNO₃ solution and subsequent photocolorimetric determination of rhenium in the eluate in the form of an orange-yellow (λ_max = 460 nm) mixes-ligand complex of Re (III) of assumed composition [Re(L)₃NOCl]–, where L — is mercaptoacetic acid anion. The developed method of rhenium determination was used in analysis of effluents of washing sulfuric acid taken from the sulfuric acid workshop of the copper smelting plant of Almalyk MMC JSC (Uzbekistan).

An increase in the cost of energy resources and urgent character of the problem of resource conservation entailes the necessity of developing means of operational control of the thermophysical characteristics of building materials, including those synthesized using nanoparticles. The goal of the study is developing of the new method for determining the thermophysical characteristics (thermal diffusivity and thermal conductivity) of building materials. The method for determining the thermophysical characteristics proposed in this article consists in measuring the temperature in two points on the sample surface subjected to thermal pulsed impact of focused microwave radiation of the given power. The number of pulses and their frequency are adaptively set by the microprocessor information-measuring system, with which the method is implemented when the temperature is reached at the setpoint control point. To implement the method, a microprocessor information-measuring system is presented. The accuracy of the proposed method is improved by controlling high temperature values, taking information in a pulse-frequency form and heating a large bulk of the material under study. The samples of clay, concrete, silicate and red brick are studied. The data obtained were compared with the results of traceable measurements of the thermophysical characteristics of the samples, using IT-λ-400 devices under laboratory conditions. The experiments showed that the developed method has several advantages compared to other traditional methods and accuracy sufficient for thermophysical measurements. The method can be used in various fields of industry and thermal engineering for construction.

The development of modern engineering is inextricably linked with the development of the new types of multilayer dielectric materials. Existing radio wave methods for monitoring interlayer defects in such materials exhibit low accuracy in reconstructing the geometric parameters of defects. The results of studying extended interlayer defects in the three-layer coating consisting of polymethyl methacrylate, F-4D PTFE, and semi-hard rubber by the method of surface electromagnetic waves are presented. The method is based on the solution of inverse problems in the reconstruction of the geometric parameters of extended interlayer defects of special multilayer materials and coatings from the frequency dependence of the attenuation coefficient of the field of a slow surface electromagnetic wave. Unlike the methods that make use from the complex reflection coefficient we proposed to increase the accuracy of the reconstruction of the geometric parameters of extended interlayer defects taking into account the linear frequency dependence of the attenuation coefficient as well as reducing the number of fixed measurement frequencies. Moreover, the determination procedure is rather simple, since only the field strength of the surface electromagnetic wave is measured, and there is no need for phase measurements. Experimental data obtained on a multifrequency measuring complex in the range of 10 – 11 GHz were used for reconstruction of the interlayer defects in the coating under study. The developed method provided a relative error of thickness estimation below 10%. The proposed method approach can be used in studying multilayer dielectric coatings on the metal for detection of delamination in the lack of glue or poor adhesion between the layers. The developed method is also suitable for control of the defects in semiconductors, ferrite and composite materials.

An engineering approach to estimation of the transverse shear stresses in layered composites is developed. The technique is based on the well-known D. I. Zhuravsky equation for shear stresses in an isotropic beam upon transverse bending. In general, application of this equation to a composite beam is incorrect due to the heterogeneity of the composite structure. According to the proposed method, at the first stage of its implementation, a transition to the equivalent model of a homogeneous beam is made, for which the Zhuravsky formula is valid. The transition is carried out by changing the shape of the cross section of the beam, provided that the bending stiffness and generalized elastic modulus remain the same. The calculated shear stresses in the equivalent beam are then converted to the stress values in the original composite beam from the equilibrium condition. The main equations and definitions of the method as well as the analytical equation for estimation of the transverse shear stress in a composite beam are presented. The method is verified by comparing the analytical solution and the results of the numerical solution of the problem by finite element method (FEM). It is shown that laminate stacking sequence has a significant impact both on the character and on the value of the transverse shear stress distribution. The limits of the applicability of the developed technique attributed to the conditions of the validity of the hypothesis of straight normal are considered. It is noted that under this hypothesis the shear stresses do not depend on the layer shear modulus, which explains the absence of this parameter in the obtained equation. The classical theory of laminate composites is based on the similar assumptions, which gives ground to use this equation for an approximate estimation of the transverse shear stresses in in a layered composite package.

Optimization of the modes of technological processing aimed at reduction or redistribution of residual stresses requires the use of modern and reliable methods of control. The method of laser interferometry leads to minor damages which are considered acceptable or can be easily removed. It is possible to use the method in industrial conditions of the workshops. Unlike physical methods, which have restrictions imposed on the classes and characteristics of materials in terms of structure, magnetic properties, and hardness, the method of laser interferometry exhibits a universal character. The method allows data saving in a digital format on speckle interferograms, thus providing a possibility of the traceability of measurement stages, expert comparison and reliable reporting. Laser interferometry provides determination of the absolute values of stresses with the error of the yield point measurement below 10%. The method can be successfully used to control the stress state in the production of critical welded structures from aluminum alloys, which are subject to stringent requirements for dimensional stability, accuracy and reliability. The technology of manufacturing the above welded structures usually includes vibration treatment, combined with the arc welding process. This technology, unlike heat treatment, is rather efficient, environmentally friendly, and low energy consumption process. Optimization of the technology plays a key role in the industrial implementation and can significantly reduce the economic costs of subsequent machining. The method of laser interferometry provides effective determination of the optimal technological mode by the parameter of residual post-welding stresses, as well as determination of the degree of the reduction of those stresses compared to the case without concomitant vibration treatment.

The goal of the study is optimization of the fracture toughness determination procedure on the samples with a chevron notch. Well-known principles of fracture mechanics are used to determine the geometry of a specimen with a chevron notch, which ensures the independence of the stress intensity factor from the crack length in the range sufficient for its practical application. A requirement to the shape of the dependence «compliance – crack length» is formulated for a chevron-notched specimen. The choice of the cross-sectional shape of the specimen with a chevron notch, the geometric dimensions of the specimen, and the drawing of the gripping device are justified. The formula for calculation of the fracture toughness from the maximum test load and thickness of the specimen is derived and experimentally validated. The results of the fracture toughness tests of the samples with a chevron notch and standard samples are compared for a number of aluminum alloys. The data on the scale factor in the range of a sample thicknesses of 12.5, 25, and 50 mm and variation coefficient obtained upon the fracture toughness determination revealed the absence of the significant effect of the scale factor, 6% variation under the normal law of the fracture toughness distribution in the tests of chevron-notched specimens. The results on the fracture toughness distribution in the height of the thick plates of alloys 1163T1 and V95pchT2 are presented. The temperature dependence of the fracture toughness of the plate (alloy 1201T1) are constructed for chevron-notched specimens within a temperature range of –196 – +200°C. The features of using chevron-notched specimens for determination of the crack growth rate attributed to independence of the stress intensity factor at the crack tip on crack length are considered in a rather wide range. The method of the crack growth rate determination is described and the results of assessing da/dN – ΔK for an aluminum alloy plate 1163T are presented. The simplicity and reliability of the methods for determination of the fracture toughness and fracture growth rate (fatigue, creep, corrosion) on chevron-notched specimen of the proposed geometry allow us to recommend them for control tests and research in various test conditions.

Since September 1, 2019, GOST ISO/IEC 17025–2019 has been enacted as a national standard in the Russian Federation. The novel standard imposes a number of fundamentally new requirements for testing laboratories (hereinafter referred to as the IL or laboratory), and also supplements and specifies the requirements previously regulated by GOST ISO/IEC 17025–2009. In this regard, in order to transfer laboratories to the new requirements, the FSA issued an order in August 2019 listing the mandatory activities that IL must fulfill to bring their activities in line with the new requirements. However, a transition period desired for matching these requirements is absent on a practical level for a number of the laboratories. The purpose of the article is to facilitate a gentle, efficient and pain-free move from the requirements of GOST ISO/IEC 17025–2009 to the new requirements of GOST ISO/IEC 17025–2019, including compliance with new changes in accreditation criteria. We carried out a comparative analysis of the requirements of the new and previous versions of the standard and marked each new and significant item to which the laboratory should pay attention first of all. The new standard focuses on the application of the process approach, risk and opportunity management, as well as on implementation of the policy of impartiality, independence, minimization of competitive interests and confidentiality. The article describes the planning, implementation and monitoring of each event or phase of the transition of testing laboratories to new requirements. Moreover, the recommendations on the structure of the «Quality Manual» and self-assessment on the compliance of IL activities and QMS with the new requirements, including the use of statistical methods for substantiation of the correctness of the assessment are given as an example of the implementation of IL capabilities.