Vol 79, No 12 (2024)

The use of X-ray spectral analysis in determining the elemental composition of medicinal plants have been considered. The review mainly presents works by Russian authors published in Russian journals and collections over the past 20 years. When determining the contents of macro- and microelements in medical plants, the authors utilize X-ray fluorescence spectrometry (XRF) with wavelength dispersion (WDXRF), with energy dispersion (EDXRF), synchrotron radiation XRF (SR XRF), total reflection XRF (TXRF), electron probe microanalysis and scanning electron microscopy. The simultaneous determination of macro- and microelements, a non-destructive sample preparation procedure and acceptable time and reagent expenses make XRF attractive in the identification and control of the chemical composition of plants, in particular, those used in medical practice. Most of the published works contain information on the sample preparation and measurement procedures, metrological estimates are given and the results obtained are discussed. However, there is no methodological information in some publications. There are typos in the presentation of analytical data.

The use of nanostructured sorbents at the stages of sample preparation (extraction, concentration) of multicomponent mixtures in the processes of solid-phase extraction of organic substances is of great interest. In the present work, the sorption properties of ordered mesoporous analogues of SBA-15 synthesized in the presence of quercetin as a potential sorbate are studied. The features of sorption isolation and concentration of quercetin, dihydroquercetin, naringin and rutin under dynamic conditions from acetonitrile solutions by the method of breakthrough curves are considered. The use of a generalized criterion for optimizing the sorption concentration of CE within the framework of the model of dynamic sorption concentration of Venitsianov – Tsyzin, taking into account the limiting (mixed-diffusion) stage of sorption kinetics, made it possible to evaluate the effectiveness of sorption concentration of flavonoids on the studied sorbents. It is shown that the use of ordered silica synthesized in the presence of a potential sorbate makes it possible to significantly increase the concentration efficiency compared with unstructured silicas, as well as samples of an unmodified analogue of SBA-15.

Conditions for determining the content of urea and humates in aqueous fertilizers in their combined pr esence by IR spectroscopy of frustrated total internal reflection are proposed. The urea and humate spectra were identified. Characte ristic bands of urea and humate were selected for their determination in the joint presence. The error in determining urea is minimal w hen registering an analytical signal at 1628 and 1598 cm^–1 (10-200 g/l), humate — at 1380 cm^–1 (10-100 g/l). When calculating the content of humate and urea in their mixtures by the Firordt method, the e rror in determining each component is 3%. The proposed determination conditions have been tested on model fertilizers and commercial humate fertilizers.

Polymer micro- and nanoparticles (microplastics) are an environmental pollutant. The low content of microplastics in such objects can affect ecosystems and human health, therefore, there is a growing need to determine microplastic particles at a low content level and simultaneously assess the physico-chemical parameters of the systems under study. Thermolensing spectrometry (TLS) was used to determine polystyrene particles with sizes of 65 and 80 nm in the concentration range of 0.0005–0.15 mg/l in their aqueous dispersions. The comprehensive registration of the TL data also made it possible to evaluate the thermal conductivity of these solutions. It has been established that an increase in the content of polystyrene nanoparticles in water leads to a nonlinear change in thermal conductivity.

Electrodes modified with gold particles, multi-walled carbon nanotubes, an ionic liquid based on 1-butyl-3-methylimidazolium hexafluorophosphate, as well as a composite based on them for the voltammetric determination of sulfamethazine, sulfacetamide and sulfathiazole have been developed. It has been established by cyclic voltammetry that modification of the surface of a glass-carbon electrode with gold particles, a composite based on carbon nanotubes and an ionic liquid leads to an increase in its effective area. The electrochemical impedance data indicate an increase in the electron transfer rate on the modified electrodes compared to the unmodified one. A composite electrode with gold particles, carbon nanotubes and an ionic liquid with the best characteristics was used for the amperometric determination of sulfonamides under batch injection conditions. The optimal parameters for the determination of sulfonamides in the batch injection system have been established. The dependence of the analytical signal on the concentration of the compounds in question in logarithmic coordinates is linear in the range from 1 × 10^–8 to 5 × 10^{– 3} M for sulfamethazine and sulfacetamide and from 1 × 10^–7 to 5 × 10^–3 M for sulfathiazole. The proposed method for the determination of sulfonamides has been tested in the analysis of medicines.