Vol 73, No 3 (2018)

The scientific achievements in the field of calculation and prediction of gas chromatographic indices of retention of organic compounds on standard nonpolar polydimethylsiloxane stationary phases of capillary chromatographic columns are analyzed. Approaches based on the study of correlation dependences with the use of physicochemical, fragment, and quantum-chemical descriptors, topological indices, and various additive models are described.

The development and use of thioether sorbents for the separation and preconcentration of metals from aqueous solutions are described. The possibilities of initial polymer thioethers in selective preconcentration and the acceleration of sorption through the introduction of nitrogen-containing groups into thioethers are considered. The dependence of the selectivity of sorbents on the nature of radical at the nitrogen atom is revealed. The use of aminothioethers with different substituents at the nitrogen atom enables distinguishing the groups of noble metals, toxic elements of arsenic and selenium subgroups, and a number of nonferrous metals in the presence of large excesses of other elements. A high recovery of the elements to be determined into the sorption preconcentrate and the selectivity of the sorbents help to improve the accuracy of the analysis. Prospects for the use of aminothioethers are considered on an example of sewage waters. It is found that the extraction of small concentrations of elements from large volumes of solutions is more convenient to carry out in dynamics, for which powdered aminothioether sorbents are not suitable. To ensure a possibility of using aminothioethers in dynamics, a “snake in a cage” synthesis method is used, in which the inert granular support is modified with aminothioether moieties. The introduction of aminothioethers with different radicals at the nitrogen atom makes it possible to combine sorbents selective with respect to different groups of elements on one carrier and thus to create a universal sorbent with predetermined properties, aimed at extracting certain metals.

A rapid method is developed for the quantitative determination of 5–35 g/L of isonicotinic hydrazide (INH, isoniazide) in aqueous media. The method is based on the formation of copper(I) oxide in the reaction of isonicotinic hydrazide with copper ions on the surface of indicator tablets and the subsequent recording of the analytical signal by reflectance spectrophotometry and colorimetry. Aluminum oxide is proposed as a solid-phase substrate for the production of indicator tablets. Isonicotinic hydrazide can be determined in the tablet form of the Isoniazid preparation.

Experimental data on the generation and detection of characteristic X-radiation of elements in electron probe microanalysis of dielectric samples in the low vacuum mode without the deposition of conducting coatings are discussed. The main advantage of the considered method of analysis is the stability of the intensity ratio between diagnostic analyte lines in the wide range of currents of the electron probe and gas phase pressure in the chamber in the range 60–130 Pa, sufficient for obtaining undistorted images of the surface of dielectrics. The stability of the intensity ratio ensures obtaining correct data of the quantitative analysis of nonconducting samples without the deposition of conducting coatings. The main features of low-vacuum microanalysis for the range of gas phase pressures used are discussed, which can create additional difficulties in the study. Among such features is a possibility of the manifestation of reflexes of gas-phase elements, significant underestimation of the relative emission intensity from lighter elements in the composition of the studied samples, loss of scanning locality in the analysis of small sites on the sample surface. An example of the correct quantitative elemental analysis of a dielectric surface without the deposition of an electroconductive coating for a number of aluminosilicates is presented.

The present study highlights the first time use of hybrid synergy electrocatalysis to design a cost effective, non-enzymatic ethanol sensor. The nanohybrid has been synthesized by decorating platinum palladium bimetallic nanoparticles (Pt‒PdNPs) on graphene nanosheets (G/Pt‒PdNPs). Field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, electrochemical measurements and UV-Vis spectrophotometry have been used to characterize the nanocomposite. An ethanol oxidation current of 332 μA was obtained with the use of G/Pt‒PdNPs modified glassy carbon electrode (GCE) that is 167 times higher than that of bare GCE in cyclic voltammetry studies with a potential scan rate of 50 mV/s in 0.1 M NaOH as the supporting electrolyte. Chronoamperometry studies have shown a distinct increase in the current for increasing concentration of ethanol with a wide range of linearity extending from 5 mM to 3 M and a detection limit of 1 mM with the use of G/Pt‒PdNPs. Quantum mechanical modeling using density functional theory was used to arrive at the minimization energies of G/Pd, G/Pt and G/Pt‒Pd in the presence and absence of ethanol. The improved catalytic activity of G/Pt‒PdNPs nanocomposite for ethanol detection is on account of the cooperative effects of Pt and PdNPs, coupled with the high conducting nature of graphene.

The most difficult task in antidoping control is the identification of compounds whose origin can be either endogenous or exogenous. This paper presents a procedure for determining the origin of 19-norandrosterone based on the extraction of target components from urine, their multistage purification by semipreparative HPLC, acetylation, and quantification by gas chromatography–isotope-ratio mass spectrometry and gas chromatography–mass spectrometry. Effects of isotope fractionation were not observed in sample preparation. The degree of extraction of the target analytes was 80 ± 5%.