Vol 79, No 8 (2024)

The first part of the review provides general information about the liquid extraction of organic compounds from solid samples and discusses various methods of its implementation: extraction in a Soxlet apparatus, ultrasonic extraction, extraction in a microwave field. Based on the analysis of the review papers, information on the features of sample preparation using these methods is systematized, experimental parameters affecting the extraction efficiency are considered, examples of the use of these methods for the isolation of organic compounds in the analysis of solid environmental objects, food and plants are given.

A new reagent based on salicylaldehyde was synthesized, its crystalline structure determined, and the complex formation of this reagent with iron(III) was studied by the spectrophotometric method. The crystalline structure of the reagent was established using X-ray structural analysis. The dissociation constant of the reagent in a water-ethanol medium was determined potentiometrically: pK = 9.66 ± 0.02. The interaction of iron(III) with 2-(((1-(3-bromophenyl)ethylidene)hydrazono)methyl)phenol was studied in the presence and absence of diantipyrylmethane (DAM), diantipyrylphenylmethane (DAFPM), and diantipyrylpropylmethane (DAPM). Optimal conditions for complex formation (λопт, pНопт) were found. It was established that iron(III) forms colored mixed-ligand complexes with the reagent in the presence of the third components – DAM, DAFPM, and DAPM, with a hypsochromic shift observed in the absorption spectrum. The maximum yield of complexes was achieved in a more acidic medium compared to the binary complex. The molar absorption coefficients of the complexes and their compliance with Beer's law were determined. The component ratios in the homogeneous and mixed-ligand complexes were established by the isomolar series method, the relative yield method of Starik-Barbanel, and the equilibrium shift method. All methods showed that the Fe(III)–R component ratio in the binary complex is 1:2, while in the mixed-ligand complexes Fe(III)–R–DAM, Fe(III)–R–DAFPM, and Fe(III)–R–DAPM, the ratios are 1:2:1, 1:1:1, and 1:1:2, respectively. The mixed-ligand complexes of iron(III) with 2-(((1-(3-bromophenyl)ethylidene)hydrazono)methyl)phenol are characterized by good chemical-analytical properties. The developed method was applied for determining trace amounts of iron(III) in oil sludge.

4-[(S)-2-Methyl-3-hydroxypropoxy]-4'-formylazobenzene, 4-(3-hydroxypropoxy)-4'-formylazobenzene, and µ-oxo dimer of iron 2,8,12,18-tetramethyl-3,7,13,17-tetra-n-amylporphyrin were synthesized using known methods. A mixture with a specified concentration of the synthesized compounds was prepared and used to impregnate a wide-pore adsorbent Chromaton N-AW. The degree of impregnation was 10%. The prepared adsorbent was used as the stationary phase for reversed gas-mesophase chromatography. Using the reversed gas chromatography method, the sorptive redistribution of a series of volatile organic compounds—methyl- and dimethylpyridine isomers, weakly polar xylenes, and enantiomers—was studied from the gas phase on the prepared adsorbent. During the experiment, specific retained volumes of sorbates, characterizing the sorptive activity of the prepared stationary phase, were calculated. Activity coefficients of sorbate distribution in the liquid layer of the liquid crystal were obtained for structural isomers. To confirm the data on sorptive activity, thermodynamic parameters of the dissolution of specific isomers were found. Conclusions were made regarding the influence of enthalpy and entropy factors on the retention capacity of the sorbates. The influence of structure, isomerism, intermolecular interactions, and the addition of a macrocycle on the sorptive characteristics of sorbates is discussed. Analytical sorption features were evaluated, and maximum values of separation factors for structural and optical isomers, as well as for compounds with different structures but close boiling points, were calculated. It was experimentally established that the prepared adsorbent exhibits sufficiently high capability for separating structurally similar isomers with close boiling points and moderate capability for enantiomer separation. Special attention was given to the maximum separation factor for 3,4- and 3,5-lutidines, which was higher than that of previously developed stationary phases of similar structure. The application of the prepared adsorbent in an integrated chemical analysis system is justified.

The gas-chromatographic retention indices (RIs) of trimethylsilyl (TMS) derivatives of the simplest amino acids on standard nonpolar polydimethylsiloxane stationary phases were systematized. This processing of data included combining them for derivatives of the same amino acids depending on the number of TMS groups (from one to four) and calculating average RI values together with their standard deviations based on data from various sources of information. This form of presenting the results made it possible to identify the best characterized derivatives and evaluate the reliability of the retention indices known for them. The simplest additive scheme for calculating retention indices based on even limited data for the most common amino acids was formed to estimate their unknown values, control previously determined values, and identify erroneous data. The increment ΔRI = RI(bis) – RI(mono) for the transformation –CO₂Si(CH₃)₃ + –NH₂ → –CO₂Si(CH₃)₃ + –NHSi(CH₃)₃ was well reproducible (118 ± 9). The other increments ΔRI = RI(tris) – RI(bis) were different for the transformations –NHSi(CH₃)₃ + XH → –N[Si(CH₃)₃]₂ + XH (238 ± 35) and –NHSi(CH₃)₃ + XH → –NHSi(CH₃)₃ + + –XSi(CH₃)₃ (111 ± 16). A method for monitoring the correctness of the obtained values of ΔRI was proposed.

This paper presents a method for the simultaneous determination of nine uremic toxins and choline in blood serum. The target substances were selected based on literature data as potential biomarkers for assessing the severity and progression of immunoglobulin A nephropathy, a kidney disease that leads to disability, and, without timely treatment, death in young and middle-aged individuals. Ultrafiltration is used to separately determine free and protein-bound indolic uremic toxins in the blood. The use of high-performance liquid chromatography combined with high-resolution tandem mass spectrometry ensures satisfactory accuracy of the analysis without complete chromatographic separation of analytes under standard reversed-phase HPLC conditions. For calibration purposes, an albumin solution in phosphate buffer was used as a surrogate for blood serum. The protein concentration of 45 mg/mL and pH 7.4 match the characteristics of native blood serum. A pilot experiment demonstrated the feasibility of determining key indicators of the gut microbiome’s state—choline and trimethylamine N-oxide (TMAO)—in dried blood spots.

Modified electrodes based on gold particles and mixed-valence ruthenium oxides, as well as a binary system based on them, were developed for voltammetric determination of ceftriaxone, cefotaxime, and cefoperazone. The electrode with the binary system of gold particles and mixed-valence ruthenium oxides, which exhibited the best characteristics, was used to detect cephalosporins under flow-injection analysis conditions. Optimal detection conditions for cephalosporins in the flow-injection system were selected. The dependence of the analytical signal on the concentration of the examined compounds in logarithmic coordinates is linear within the range from 5 × 10^–7 to 5 × 10^–3 M. The proposed method for determining cephalosporins was tested during the analysis of pharmaceutical products.