Vol 78, No 2 (2023)

A summary of the accumulated experience of using chromatomembrane methods (CMMs) for automation of the chemical analysis of water and air media is presented. Particular emphasis is placed on flow-through methods of continuous analysis, where chromatomembrane methods often have no alternative.

Samples of complex composition usually contain similar organic compounds, molecules of which differ in the composition and structure but are characterized by common features (structural, functional, chemical analytical, etc.), uncharacteristic for other compounds. summary concentration of similar compounds are figures of the group composition of a studied sample. Procedures for their determination are widely used in analytical control and research laboratories. A special type of chemical analysis, group analysis (GA) was developed by the end of the 20th century. Structural group analysis (SGA) is considered an important special case of GA. Unfortunately, the methodological and metrological aspects of GA and SGA have been studied insufficiently. A conventional system of terms in this field also has not been developed. This paper considers the system of terms and the history GA, principles of group formation, and methods of the assessment of summary concentration. The unresolved problems of GA are emphasized. These are the uncertainty of the qualitative composition of groups, hindering the interpretation of the results of group analysis, and also intragroup selectivity and nonadditivity of the analytical signals. Possible solutions of these problems are considered.

We studied the effect of chemically active fluorine-containing additives AlF3, BaF2, and ZnF2 on the character of evaporation of some low-volatile elements from a refractory matrix in the crater of a DC arc electrode in the analysis of zirconium by atomic emission spectrometry. The additives cause the formation of volatile fluorides of low-volatile elements and their fractional evaporation with respect to the base element evaporation. Impurity fluorides rapidly and completely evaporate during the first 30 s of arcing, and only after that the intensive evaporation of the base begins. Such fractionation increases significantly the intensity of the spectral lines of impurities, decreases the background intensity, and, consequently, improves the limits of determination of low-volatile elements in zirconium oxide. Zinc fluoride is the most effective of the studied additives. Using zinc fluoride, we lowered the limits of determination of low-volatile elements by two orders of magnitude compared to the limits of determination in zirconium oxide without additives and improved the reproducibility of the results of determinations.

An automated method is developed for dispersive liquid–liquid microextraction of fluoroquinolone antibiotics based on the principles of stepwise injection analysis. The method involves the dispersion of the extractant by the gas phase, formed in situ in the extraction chamber of the flow analyzer. A deep eutectic solvent based on a terpenoid and a mixture of hydrophilic and hydrophobic carboxylic acids is studied as an extractant for the isolation and preconcentration of fluoroquinolones, and a possibility of its use is substantiated. Hydrophilic carboxylic acid in the composition of the extractant acts as a proton donor for the formation of a carbon dioxide dispersant in the presence of sodium carbonate dissolved in the aqueous phase. A possibility of combining the developed method with high-performance liquid chromatography with fluorimetric detection is shown on an example of the determination of fluoroquinolones in wastewaters. The limits of detection (3σ) for ofloxacin, fleroxacin, and norfloxacin were 0.3 µg/L.

A procedure is proposed for the extraction of 2,6-diisobornyl-4-methylphenol (IBP), the molecule with potential multi-target activity, and its active metabolite 2,6-diisobornyl-4-hydroxymethylphenol (IBP–OH) from human and rat plasma samples for further determination by liquid chromatography–tandem mass spectrometry. The solubility of IBP (in mg/mL) in various organic solvents is determined. In particular, the compound is readily soluble in chloroform (346 ± 14), methyl tert-butyl ether (98.6 ± 3.8), and ethyl acetate (96.8 ± 2.0). It is shown that the use of a mixture of chloroform and isopropanol (5 : 1, v/v) as an extraction system with simultaneous protein precipitation makes it possible to extract only 66 ± 10% of IBP, while the recovery of IBP–OH is 96 ± 7%. Pre-dilution of 200 µL of plasma with 300 µL saline increases IBP recovery to 100 ± 4%. Drying the extracts in a vacuum concentrator (air, 45°C) with the further reconstitution of the residues in 300 μL of acetonitrile facilitates the purification of biosamples and the preconcentration of analytes. The total sample preparation time does not exceed 70 min, and the duration of an analysis is 7 min, the injection volume is 2 µL. The procedure has been successfully tested on actual rat plasma samples after a single oral administration of IBP (10 mg/kg in oil) in the framework of pharmacokinetic studies.