Chemistry

Chromatographical Analysis of Meldonium with Preliminary Concentration by Solid-Phase Extraction on Magnetite Nanoparticles

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. It was found that quantitative sorption proceeded in 20 min with a meldonium extraction degree of 88%.

Optimization of the Conditions for Determining 2,4-D and Deltamethrin by HPLC

The paper presents the results of optimizing the conditions for the chromatographic determination of 2,4-dichlorophenoxyacetic acid and deltamethrin for two capillary columns (Supelcosil LC-18, Kromasil C-18). The modes of individual chromatography of pesticides were selected. The use of the isocratic elution mode in the joint presence of 2,4-dichlorophenoxyacetic acid and deltamethrin was shown and experimentally proved to be invalid. Three options were proposed for the conditions of the gradient mode of the separate detection of analytes in a mixture.

Synthesis and Heterocyclization of 4-Hydroxy-3 - ((2-hydroxy-4,4-dimethyl-6-oxocyclohex1-en-1-yl) (aryl) methyl) -2H-chromen-2-ones

The possibility of obtaining asymmetric 1,5-diketones based on 4-hydroxy-2H-chromen-2-one and dimedone by three-component condensation in the presence of L-proline as a catalyst is shown. As a result, a series of 4-hydroxy3 - ((2-hydroxy-4,4-dimethyl-6-oxocyclohex1-en-1-yl) (aryl) methyl) -2H-chromen-2-ones was obtained with a yield of 25 up to 73%. The study revealed that the highest yield was observed for compounds containing fragments of ortho-substituted aldehydes capable of forming a hydrogen bond. For meta- and para-substituted – the lowest yield was observed.

Application of Mathematical Model of Adsorber for the Development and Optimization of Adsorption Modes

A mathematical model of the adsorber was developed using the Toth equation. Microporous mordenite was synthesized to confirm model validation. The structure and characteristics of the obtained sorbent were confirmed by SEM, N2 adsorbtion, XRD and XRF methods. Adsorption of the hydrogen-methane mixture on H-form of synthesized mordenite was carried out at the pressure of 2 MPa and the temperature range of 20–35 °С. Based on the mathematical model of the adsorber, the possibility of developing a process for separating a mixture of hydrogen and methane at high pressure was shown.

Physico-Chemical Principles of Structure Formation of Gypsum Binding Materials

The article shows the results of the study of composite materials obtained by the modification of mineral resources with active mineral components, which is the main direction in the production of new materials of high quality. In this work, binding materials were obtained on the basis of construction gypsum and carbonate drilling sludge, which is a retarder of the setting time as well. The physical and chemical properties, the structure of the system, and the phase influence of the modifier on the structure and hardening of the obtained new materials were investigated.

Density Calculation for Mixture Melts of LiF + NaF

Salt mixtures are used as molten electrolytes of chemical current sources, solvent melts of inorganic substances, heat storing compositions, fluxes for welding and soldering. Modern coolants include alkali metals and their halogenides. Lithium-containing thermofors have a special place. Density is one of the important properties of the melts used. The paper presents the analytical description of the density for the mixture melts of LiF + NaF of various compositions in the temperature range of 1130 ... 1320° K.

Pre-Concentration and Extraction of Samarium Isotopes by Precipitation of Slightly Soluble Hydroxides and Fluorides of Metals

The comparison and assessment of the efficiency of using the precipitation of sparingly soluble metal hydroxides and fluorides for the extraction and pre-concentration of samarium isotopes from the solution simulating acidic leachate of the soil were made. It was shown that the precipitation of samarium isotopes was achieved quantitatively at the pH of about 7 and the co-precipitation of alkaline and alkaline earth elements did not exceed 20%.

The Investigation of Benzimidazoles’ Sorption on Modified Silicagels and Hypercrosslinked Polystyrene by HPLC

The production of good-quality, effective and harmless pharmaceutical products and import substitution of drugs are of top priority for the pharmaceutical industry. Benzimidazole and its derivatives are active substances of many drugs due to the wide range of their pharmacological activity. In the article under consideration the sorption of the newly synthesized benzimidazole’s derivatives from liquids media was studied. Reverse phase high performance liquid chromatography (RP HPLC) is the most appropriate method used for the analysis of biologically active substances, particularly drugs.

Improvement of Potentiometric Determination of Ammonium Ions in Surface Waters for the Samples with a High Concentration

The problem of choosing a technique for determining ammonium ions, in concentrations above 1 gm/cdm, in surface waters, as in complex matrix, is one of the important problems of monitoring the condition of water bodies contaminated with ammonium salts. The solution to this problem will allow us to reliably assess the ecological condition of water bodies and the degree of reduction of environmental load during pollution elimination measures.

Modified Potentiometric Sensors of Various Types for Ceftriaxone Determination

The planar unmodified and modified by polyaniline, nanoparticles and their binary mixtures potentiometric sensors of various types were manufactured on the basis of tetradecylammonium associates (TDA) with complex connections silver (I) – ceftriaxone (Ag (I) – Ceftr). In sensors of I type electroactive components (EAC) and modifiers were brought in carboniferous ink. The polyvinylchloride plasticized unmodified and modified membranes on the basis [Ag2 (Ceftr)2] 2- · 2TDA were used in the sensors of II type; C (EAC) = 1,2,3%.

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