Hydroxycinnamic acids, including caffeic and chlorogenic acids, are widely found in plant extracts and demonstrate significant biological activity, making them promising for pharmaceutical and food industry applications. However, their natural origin and tendency to degrade during storage requires quality control, including the identification of impurities and degradation products. This study explores the potential of gas chromatography – mass spectrometry (GC-MS) for the analysis of pure caffeic and chlorogenic acid samples in order to detect impurities of various origins. It demonstrates that GC-MS analysis of acids without derivatization is not feasible due to the high polarity and thermal instability of the compounds under study, which leads to their decomposition under chromatography conditions. To improve volatility and thermal stability, derivatization was performed using N,O-bis(trimethylsilyl)trifluoroacetamide in the presence of trimethylchlorosilane, which increased the method’s sensitivity. Mass spectral analysis of the derivatized samples, supported by library searches, revealed the presence of various cinnamic acid derivatives, as well as an unidentified peak, presumably corresponding to the trimethylsilyl derivative of trihydroxycinnamic acid. The results demonstrate the effectiveness of GC-MS with prior derivatization for the detailed analysis of pure hydroxycinnamic acids and confirm its suitability for quality control and stability studies of these compounds.

To control the excretion of beta-agonists used to accelerate the growth of muscle mass in animal husbandry, a method of determination of 20 compounds of this series in the cattle urine and blood, and 12 compounds in the cattle hairs samples by high-performance liquid chromatography – tandem mass spectrometry has been developed. The sample preparation of cattle urine included enzymatic hydrolysis in a phosphate buffer followed by purification using solid-phase extraction with a Copure C8/SCX sorbent. For the blood samples extraction of analytes by acetonitrile and acetic acid, followed by a phase separation and purification using C₁₈ and aluminum oxide were carried out. Hair samples were subjected to an alkaline hydrolysis, and the analytes were extracted using methyl tert butyl ether. The extract was then transferred to acetonitrile for further dispersive purification. The overall loss during sample preparation ranged from 27 to 85% for blood samples and from 2 to 80% for urine samples, depending on the compound being determined. Chromatographic separation was conducted in a gradient mode using an ACQUITY UPLC HSS C₁₈ column. Detection was performed in the selected reactions monitoring mode with registration of at least two product ions for each compound. The detection ranges of beta-agonists in urine were 0.25 – 20.0 μg/kg; 0.1 – 10.0 μg/kg in blood; 0.5 – 20.0 μg/kg in hairs depending on the analyte. For urine and blood analysis, the relative expanded uncertainty values ranged from 9 to 25%, while for hair analysis, they ranged from 9 to 30%.

A method for the determination of 18 polycyclic aromatic hydrocarbons (PAHs) in soils and sediments has been developed, combining the QuEChERS technique of analyte extraction with subsequent determination by HPLC with fluorescence and diode array detection (FLD/DAD). The limits of HPLC-FLD/DAD quantification of analytes were established, which amounted to 0.015 – 1.0 μg/kg while recoveries were 80 – 100%. The relative standard deviations of the repeatability and reproducibility of the PAHs determination method ranged from 1.5 to 10 and from 2.3 to 12%, respectively. The metrological characteristics of the proposed approach were compared with the corresponding values for the PAHs determination by gas chromatography – mass spectrometry also in combination with the QuEChERS technique: the quantification limits of a number of PAHs have been reduced by two orders of magnitude. An optimized scheme for the determination of PAHs in soils has been tested in the analysis sand samples collected on the Black Sea coast after the emergency flooding of fuel oil tankers. PAHs of various molecular weights were identified: 2-methylnaphthalene, phenanthrene, fluoranthene, pyrene were predominant among the light PAHs, while the heavy PAHs were primarily represented by triphenylene, chrysene, and benzo[b]fluoranthene. The total content of certain PAHs in the sand samples did not exceed 10 μg/kg, close to the level of background pollution.

The possibility of determining the speciation of tantalum and niobium in various compounds (metallic Ta and Nb, TaH, NbH, Ta₂O₅, and Nb₂O₅) using the ratio of the intensities of the characteristic emission lines of these elements was investigated. The «Spectroscan Max-GVM» commercial medium-resolution X-ray fluorescence spectrometer was used for experiment. Tantalum L-series lines in the range of 1000 – 1450 mÅ and niobium L-series lines (5000 – 5400 mÅ) were used to calculate the relative integral intensity. Since the difference in the ratios of characteristic emission lines intensities for different element speciation are small, special attention was paid to spectra processing for selection of smoothed line intensities in the spectral ranges chosen. The proposed approach allowed to distinguish Ta compounds using both the intensity ratios of high-lying/low-lying transitions and two low-lying transitions. It was also possible to distinguish all three of Ta speciation forms using the ratio of the most intense (Lβ_2,15/Lβ₁) lines of the L-series. In the case of Nb, it was possible to distinguish the oxide from the pure metal and its hydride by the ratio of NbLγ₁ and NbLβ_3,4 intensities, however the proposed approad didn’t allow to distinguish the metal from its hydride. The proposed spectral recording mode is compatible with the mode used in the standard X-ray fluorescence analysis scheme, which, in principle, allows the determination of the elemental composition and form of presence of analytes in a single experiment.

Currently, there is a growing need for environmental monitoring and industrial safety, and, accordingly, for cost-effective, selective and stable sensor systems capable of promptly detecting even low concentrations of toxic components. The paper presents the results of a study of thin-film sensor materials based on biopolymer matrices of polysaccharides modified with AgI nanoparticles. The materials are intended for highly sensitive determination of ammonia in the air. The relationship between the structural and morphological characteristics of composite films containing AgI nanoparticles and their functional sensory properties with respect to ammonia vapors was analyzed. Particular attention was paid to studying the mechanisms of sensory response and the effect of surface morphology on the sensitivity of the material. Atomic force microscopy and electrophysical measurements have shown that the introduction of AgI nanoparticles significantly modifies the film surface, forming a developed relief with nanoparticle agglomerates (50 – 200 nm in size), a porous structure and an increased specific surface area (roughness increases by 3 – 5 times). Such morphological changes have been shown to significantly increase the sensitivity of the material to ammonia due to an increase in the area of active adsorption centers. Ammonia is detected due to a reversible complexation reaction between Ag⁺ ions and NH₃ molecules, which changes the conductivity of the composite. High dynamic characteristics of the sensor have been established (the response time does not exceed 8 sec at an NH₃ concentration of 50 ppm, and the recovery time is about 30 sec). In addition, the developed materials are selective for ammonia in the presence of potential interferents (CO₂, H₂O, volatile organic compounds). The results obtained can be used to create a new generation of gas sensors.

For quantitative analysis of X-ray absorption in the range of wavelengths from few to quarter part of angstrom (which approximately correspond to energies from 5 to 50 keV) and X-ray detectors calibration the source of monochromatic radiation is necessary. We present the studies of the monochromator setup constructed for the wide range of energies. The principle of the developed device is based on the X-ray diffraction effect. Pyrolytic graphite single crystal is applied as a diffracting element in the setup. When it is rotated to the assigned angle the monochromatic part is selected from the bremsstrahlung spectrum of the X-ray tube. During the testing procedures it was revealed that the presented system provides a monochromaticity of X-ray beam in the range of energies 15 – 100 keV at level of 1.5 – 9% (suitable for calibration and testing of detectors). It is also shown that available laboratory components applicable for generating tunable monochromatic radiation. The obtained results can be used in defectoscopy, tomography and other tasks which require spectral-selective X-ray analysis.

Intermetallic iron-aluminium alloys are used mainly as wear- and corrosion-resistant coatings intended for use in chemically aggressive environments or at elevated temperatures. At the same time, the alloys are characterized by brittleness at normal temperatures, uneven structure and properties of the contact zone of the intermetallic material with the base. The paper presents the results of a study of the properties of experimental iron-aluminium alloys. The influence of the initial composition of thermite charges on the parameters of the aluminothermic remelting process, the properties of cast samples and their stress-strain state under uniaxial loading was analyzed. The methods of etching microsections of the alloys were determined depending on the aluminum content in them, which is 7.35 – 58.5 % wt. It was found that samples obtained from thermite charges with an active aluminum content of up to 45 % wt. have high resistance to compressive loads. The obtained results can be used to solve problems of processing technogenic formations (scale, non-ferrous metal shavings, etc.) and forming functional surfaces and cast products from them while maintaining operational characteristics under normal conditions.

When designing building structures, due to the increase in their complexity, level and variability of loads caused by the development of industry, the task of determining the exact values of deformations is relevant. The values of deformations are inextricably linked with the values of stresses in structural materials, the level of which determines the strength and safety of buildings and structures in operation. The processes of deformation development are quite complex and depend on many factors, while one of the known methods is more often used to register them during testing of building structures. Each of these methods has its advantages and disadvantages, and an integrated approach with their combined application allows you to get a more complete picture of the processes of deformation and crack development in a reinforced concrete element. The purpose of the work is to increase the strength and reliability of reinforced concrete elements through a comprehensive analysis of the development of deformation and cracking processes using electrotensometry methods, digital image correlation and registration of thermal emissions. Research methods: experimental studies, digital image correlation method, thermal imaging method, strain gauge method. Results: A methodology has been developed, test tensile tests of a reinforced concrete sample have been planned and carried out to obtain deformation data using three methods using a thermal imager, a Vic-3D system and strain gages. The experimental data obtained are presented and analyzed. A comprehensive comparative analysis of the results obtained was carried out, the advantages and disadvantages of the proposed approach were identified. Further ways of developing the proposed methodology are outlined.

Important strength characteristics of fiber-reinforced composites with polymer matrix include their resistance to delamination and splitting, which is traditionally determined in bending of short beams (in terms of interlayer shear strength) or specimens with artificial delaminations (in terms of critical energy release rate, i.e., specific work of delamination). The implementation of these techniques is associated with known difficulties in interpretation and comparison of results. The method of determining the critical value of the stress intensity factor at the occurrence of delamination crack near the apex of the transverse layer notch is proposed in this paper. It allows: to compare the crack resistance of various composites and metals, to estimate the potential strength of unidirectional fiber-reinforced composites at fracture by the mechanism of multiple splitting, to formulate the requirements of «equal strength» under the condition of simultaneous occurrence of different types of fracture. Experimental results on the resistance to delamination of composites with different reinforcement schemes in terms of the critical stress intensity factor at crack rotation and their comparison with the interlayer strength of the material are presented.

Long-term and safe operation of complex mechanisms and aggregates requires timely diagnosis of friction units. The paper presents the results of determining the moment of friction in self-lubricating sliding bearings based on temperature data. A system of sliding bearings made of a polymer composite material supported by a rotating shaft was studed. A mathematical model of the thermal process in the system under consideration is given, taking into account the spatial distribution of temperature and its change over time. The temperature was recorded with thermocouples at several points of each bearing. The moment of friction was determined by frictional heat generation using a solution to the inverse problem of heat transfer (the condition is the proximity of measured and calculated temperatures). Temperature data with measurement errors were statistically processed. The refinement of the solution of the inverse problem was stopped when successive approximations converged. To ensure continuous data processing and determination of the moment of friction during long-term tests, the inverse problem of heat transfer was solved in consecutive short time intervals, then the solutions obtained were «glued together». It is shown that the discrepancy between the values of the total moment of the friction force obtained by calculation from temperature data and measurement by an inductive sensor does not exceed 15%. The proposed method of thermal diagnostics of friction can be used to determine the friction moments in self-lubricating sliding bearings under conditions of bench and operational tests of friction units of machines and mechanisms, as well as to increase the reliability of diagnostics of the technical condition of bearings.

When planning statistical studies, it is often necessary to determine the required sample size. The rules for finding the required sample size are quite widely discussed in the works of specialists in various fields of science and practice — engineering and technology, economics and management, medicine, sociology, etc. However, usually only individual specific statements of the problem are considered, and certain recipes for calculating the required quantity are given without justification. sample size, and often erroneous. The article is devoted to the strict formulation of methods for calculating the required sample size, developed to date, as well as the justification of the corresponding algorithms from the standpoint of modern applied mathematical statistics. Four approaches are considered. In the first of them, the sample size is determined by the available resources (material, financial, personnel, etc.) that can be used to obtain sample elements (measurements, observations, analyses, experiments, tests, surveys). In the second, problems of estimating the theoretical characteristics of a random variable are considered. The required sample size is determined by the specified estimation accuracy, by which we mean the half-width of the confidence interval. The third approach is based on the theory of statistical hypothesis testing. We are talking about choosing between the null and alternative hypotheses, based on the level of significance and power of the criterion. One-sided alternatives are discussed in detail. The fourth is developed within the framework of interval data statistics. It developed a general approach based on the principle of equalizing statistical and metrological errors. Based on the known accuracy of the initial measurements, we determine the rational sample size, which is necessary from the point of view under consideration. As basic examples, the rules for calculating the required sample size when studying probability values and mathematical expectations are considered. Limit theorems of probability theory and mathematical statistics are used as the basis of the mathematical apparatus. In further research, it is advisable to study the rate of convergence in the obtained asymptotic expressions and consider finite sample sizes.