Vol 79, No 7 (2024)

A highly sensitive sensor based on carbon fiber paper modified with a shungite–copper formazanate composite is presented for the voltammetric determination of lidocaine. The synthesized organometallic complex, composite, and modified electrode are characterized by infrared spectroscopy, high-resolution mass spectrometry, elemental analysis, scanning electron microscopy, and cyclic and linear sweep voltammetry. The twofold increase in the current of the lidocaine oxidation peak on the modified electrode compared to the unmodified one is associated with the sensitizing effect of the composite modifier, which is due to an increase in the electroactive area and the number of lidocaine binding sites on the electrode surface. The sensor exhibits a wide dynamic range from 2 to 2120 µM with a low limit of detection of 0.18 µM lidocaine and high sensitivity of 0.755 µA/V µM. The interelectrode and intraelectrode repeatability of the analytical signal do not exceed 3.5%. The sensor response is stable within three weeks. The developed sensor was used for the determination of lidocaine in pharmaceuticals. The results of an analysis of real samples demonstrated good reproducibility (RSD ≤ 5.5%) and recovery (98–102%).

The high catalytic activity of arenediazonium, along with the ability of gold ions to form specific bonds with amikacin, has been used in the fabrication of an electrochemical sensor based on a glassy carbon electrode modified with a gold solution and arenediazonium tosylate (Ar/GGCE) for the detection and quantification of amikacin upon its release from implants. Atomic force microscopy, cyclic voltammetry, and square-wave voltammetry were used to demonstrate that the use of a gold solution and arenediazonium tosylate for the surface modification of a glassy carbon electrode significantly enhances the electrode characteristics. The determination of amikacin was achieved using square wave voltammetry, which enabled the detection of amikacin at the Ar/GGCE in the concentration range 0.2–60 μM and ensured a limit of detection of 0.058 μM for amikacin released from implants.

The control of oxygen and carbon dioxide concentrations in an airflow released from a reactor, in which a sample is heated, can be used to investigate the thermal stability of polymer materials. This approach, known as oxithermography, involves analyzing experimental data (oxithermograms), representing the variation in oxygen concentration decrease and carbon dioxide appearance in an airflow with changing temperature conditions. This method allows for monitoring the effect of fillers introduced into polymer compositions on their thermal stability. The application of oxithermography to studying oxidative thermostability is demonstrated using pure polypropylene and polypropylene with titanium dioxide admixtures as examples.

A method for obtaining effervescent tablets, consisting of magnetic carbon, tartaric acid, sodium carbonate and sodium bicarbonate, and their use for the adsorption of dichlorophenoxycarboxylic acids (DCPA)—2,4-dichlorophenoxyacetic, 2,4-dichlorophenoxypropionic and 2,4-dichlorophenoxybutyric acids and their metabolites—2,4-dichlorophenol and 4-chlorophenol is proposed. The tablets are immersed in an analyzed solution with a neutral reaction medium. To analyze soils, extraction with an alkali solution followed by the neutralization of the extract is carried out. After CO₂ separation is completed, the sorbent is removed with a neodymium magnet and the analytes are desorbed with acetone. The acetone extract is evaporated under a stream of nitrogen, and the concentrate is analyzed by gas chromatography–mass spectrometry. The method was tested on model systems—samples of river water and typical chernozem, which were artificially contaminated with DCPA and chlorophenols (CP). In analyzing river waters, the limits of determination for DCPA are 0.7–0.9 μg/L, for CP—40 ng/L. In soils, the limit of detection is 3–4 and 0.1 μg/kg for DCPA and CP, respectively.

The paper presents the results of assessing the sorption and fluorescence properties of compounds from the azolotriazine class and phases based on cadmium sulfide quantum dots in the presence of volatile organic compounds (biomarkers of the state of living systems). The sorption properties of phases based on organic dyes and encapsulated semiconductors in relation to vapors of alcohols, ketones, amines, acids, ammonia, and aldehydes were studied using direct high-sensitivity quartz crystal microgravimetry. Spectral properties and their changes in the presence of analyte vapors were studied using various spectroscopic methods (absorption, photoluminescence). The results of these studies and the possibility of optimizing this stage were compared. It is proposed to evaluate the consistency of methods for predicting changes in fluorescence properties in test systems for volatile organic compounds using Kendall’s W concordance coefficient. It was found that the highest concordance coefficient (W = 0.89) was obtained with the methods of spectrofluorimetry and direct vapor microgravimetry when sorption occurs on phases—potential fillers for test systems. The correlation of results obtained by different fluorescence methods (visual plate test systems and fluorimetry of phases on paper substrates) is 0.80, which confirms a high degree of consistency in assessing the interaction between analytes and organic, combined fluorochromes. It was established that methods similar in the nature of their analytical response are not better aligned with each other than with the method of direct vapor microgravimetry on microphases of fluorimetric reagents of different natures (CdS/chitosan quantum dots, organic compounds of the azolotriazine class, mixed phases). This, in turn, allows for the selection of simpler, more accessible, and rapid methods and tools for analysis during routine experiments.