Vol 78, No 1 (2023)

We present a critical review of experimental studies of the efficiency of the separation of various groups of chemical compounds under the conditions of high-performance liquid chromatography using metal-organic framework polymers (metal-organic frameworks (MOFs)) or composite materials with MOFs as a stationary phase. MOFs demonstrated many advantages in high-performance liquid chromatography and a possibility of competing successfully with conventional phases, especially in the determination of low-molecular-weight compounds and optical isomers. Among the promising options for using this class of materials are the development of monolithic separation columns and hybrid adsorbents that eliminate the disadvantages of adsorbents based on pure MOFs.

A simple and an available method is proposed for the identification and authentication of milk using a test device, a smartphone, and chemometric analysis. For the identification by the region of origin and the species of milk (cow, goat, sheep, etc.) and authentication (authenticity, falsification of milk), acid-base indicator papers and test papers are used to determine the total hardness and total alkalinity of water and chloride and sulfate ions. Two indicator systems are proposed. In the first test system, 16 indicator zones are used, of which 12 zones are acid-base indicators with a color change in the pH range of 3–9, and 4 are indicator zones, the color change of which depends on the concentration of calcium ions and chloride, sulfate, carbonate, and hydrocarbonate ions. The second test system uses fluorescent indicators, as well as the intrinsic fluorescence of milk on cellulose paper and a thin silica layer. In this case, the indicator zones of the matrix are irradiated with monochromatic ultraviolet light (365 nm) after applying milk samples to them. A device and a method for measuring the colorimetric characteristics of test systems using a smartphone are proposed. The data array (the sum of the RGB channel values) is processed using the XLSTAT software. The use of chemometric analysis made it possible to establish the authenticity of milk, identify it by the region of origin, and reveal facts of milk falsification by dilution with water, the use of vegetable fats, and emulsification with surfactants. The manufacturers of pasteurized milk were identified and a possibility of determining its fat content by the data array of RGB colorimetric parameters is proved

It was found experimentally that the replacement of acetonitrile with ethanol upon the acidification of the mobile phase with phosphoric acid is an effective version for replacing acetonitrile. At that, the order of elution of glycosides of the same type of the five main anthocyanidins (delphinidin, cyanidin, petunidin, peonidin, and malvidin) does not change in eluents convenient for analysis, and the range of retention times for a complete set of such anthocyanins becomes noticeably narrower in going from acetonitrile to ethanol. To determine the effect of aglycone structure on the retention of derivatives of the same anthocyanidin (cyanidin), a mixture of six glycosides was used: one monoglycoside (3-glucoside), two 3-diglycosides (sophoroside and sambubioside), and two 3-triglycosides (2"-glucosylrutinoside and 2"-xylosylrutinoside). This mixture is a real set of anthocyanins, requiring the careful selection of the mobile phase for separating all components. In this work, based on an analysis of separation maps, the composition of a mobile phase based on ethanol is determined that ensures the achievement of the effective separation of these anthocyanins.

We studied the regularities of gas-chromatographic retention indices of aliphatic enyne alcohols containing С=С and С≡С bonds in the molecule (14 secondary and two tertiary homologues) on standard nonpolar polydimethylsiloxane stationary phases, which have not been characterized in sufficient detail earlier. Using homologous increments of retention indices iRI = RI – 100x, where х = int(M/14), М is the molecular weight number, and 14 is the mass number of the CH2 homological difference, one can compare data for structural analogs, including alkanols, alkenols, and alkynols. The features of comparing iRI values for compounds belonging to different homologous groups y ≡ M(mod14), for example, CnH2n+2O (y = 4), CnH2nO (y = 2), CnH2n–2O (y = 0), and CnH2n–4O (y = 12), are discussed. The main feature is that when the boundary value of y = 0 is passed, the relation between the parameter x and the number of carbon atoms in the molecule changes due to an increase in the formal unsaturation (the condition n = x – 1 is replaced by the condition n = x). Therefore, in the latter case, 100 should be subtracted from the iRI homologous increments to compare them with the data for structural analogs of other series. Taking this correction into account, we found that the iRI values for secondary enyne alcohols (12 ± 16) and previously characterized sec-alkynols (23 ± 21) virtually coincide, and for tertiary enyne alcohols, they are consistent with the data for all considered groups of structural analogues (alkanols, alkenols, and alkynols).

The results of the determination of sulfur-containing compounds in atmospheric air polluted by products of the depressurization of a product pipeline with gas condensate are presented. Hydrogen sulfide was determined online using mobile automatic control stations and by photometry in a stationary laboratory. Organic sulfur-containing compounds (mercaptans, sulfides, disulfides) were identified by chromatography–mass spectrometry. It was found that the results of the analysis obtained in the automatic mode reflect the total content of hydrogen sulfide and some organosulfur compounds.

A new type of potentiometric sensor for cesium ions based on a crown ether (dibenzo-21-crown-7) is proposed; its analytical characteristics are presented: limit of detection, slope of electrode function, selectivity to a number of interfering ions, and the working pH range of solutions.