Химия

A comprehensive method for meldonium analysis, based on a combination of magnetic solid-phase concentration of the analyte on magnetite nanoparticles modified with cetylammonium bromide (CTAB) cations and its subsequent analysis by thin-layer chromatography (TLC) were developed in the process of study. The influence of a number of factors on meldonium sorption was studied, namely: pH, sorbent mass, sorption and mixing times; optimal extraction conditions were determined.

The results of the study of the morphology and surface topography of chitosan films of the salt (S-) and basic (B-) chemical form by atomic force microscopy are presented. The films were cast from polymer solutions in acetic, lactic, citric and succinic acid. NaOH and triethanolamine were used for the salt > chitosan base reaction. Surface tomograms were obtained; the main morphological characteristics and roughness parameters of the film samples were estimated.

Visual polythermal method in the bynary system of water-2-(2-butoxyethoxy) ethanol in the range of –25?0° C the ice melting line is determined and the phase equilibria in the ternary system potassium nitrate–water–2-(2-butoxyethoxy) ethanol are studied in the range of 10.0–90.0° C. The ice melting line in the water–2-(2-butoxyethoxy) ethanol binary system is a flat, smooth line. This form of the melting line shows a hidden separation in liquid mixtures.

A comparative analysis of the results of our polythermal study of the ternary systems sodium (potassium, cesium) nitrate – water – triethylamine has been carried out to estimate the efficiency of the use of triethylamine in the extractive crystallization of alkali metal nitrates from water–salt solutions containing 43.0, 44.0, 45.0, 46.0, and 47.0 wt. % sodium nitrate in the range of 10.0–25.0°C, 20.0, 21.0, and 22.0 wt.% potassium nitrate and 18.0, 19.0, 20.0 and 21.0 wt. % cesium nitrate in the range of 20.0–25.0°C.

The sorption properties of glauconite from Beloozersk deposits (Saratov region) for 4-nitrophenol (4-NF) have been investigated. The effect of glauconite on pH and 4-nitrophenol structure in solution is estimated. It is shown that glauconite increases pH of aqueous environment to 8 and shifts the equilibrium towards the formation of aci-form 4-NF. The conditions of sorption 4-NF by glauconite are established: the sorption time 20 min, the mass of the sorbent (0.50–1.0) g.

Colloidal quantum dots (QDs) of lead sulfide have been synthesized and investigated using octadecene and white spirit as a solvent for sulfur, varying the concentration of precursors and the temperature of the process. A method has been proposed for the synthesis of these QDs using anhydrous white spirit as a solvent at a temperature of 200° C, which made it possible to obtain polygonal nanoparticles with an average diameter of 2 to 3.2 nm with a minimum spread in size (± 10%).

The 1st generation cefalexine-cephalosporine antibiotic is used in the treatment of various infectious diseases. Spectrophotometry, kinetic spectrophotometry, spectrofluorimetry are proposed to determination of cefalexine in medicine and biological environment. Planar screenprinted sensors allow analyzing the micro-volumes of samples, which is important for the analysis of biological objects without preliminary samplepreparation. Depending on the active material and modifiers, you can create planar sensors for the determination of different organic compounds.

Aryl-substituted triazolohexahydroquinazolines have been synthesized by means of three-component condensation of pnitro(pbromo) benzaldehydes, cyclohexanone, 1,2,4-triazol-3-amine. A scheme of the reaction mechanism is proposed, which makes it possible to explain the features of the behavior of p-nitro(bromo) benzaldehydes in condensation reactions in comparison with their ortho-substituted analogs.

For the efficient preconcentration of azo compounds – products of the interaction of 4-nitrophenyldiazonium with thymol, a system 4-nitroaniline (4-NA) – NO2 - – Triton X-100 – NaOH – ethanol has been proposed. The optimal conditions for the formation of micellarsaturated phases of the system under study have been established: 3. 10-4 M 4-NA – 3. 10-4 M NO2 - – 5% Triton X-100 – 2.8 M NaOH – 10 vol. % С2Н5ОН. A spectrophotometric study of the above system has been carried out.

Test means based on immobilized Fehling’s reagent for the determination of cephalexin have been obtained. Methods for visual and colorimetric assessment of antibiotic concentration using a smartphone camera have been developed. The optimal conditions for the indicator reaction have been selected with varying heating time and temperature. For a visual semi-quantitative assessment of the content of cephalexin, a color scale has been obtained.