Recent advances in gas chromatography for solid and liquid stationary phases containing metal ions

Effect of silver(I) ion reduction on the selectivity of olefins, paraffins, and aromatic compounds by gas chromatographic stationary phases consisting of silver(I) salts in ionic liquids

The olefin/paraffin selectivity offered by ionic liquid (IL) stationary phases can be enhanced through the addition of silver(I) ion, which is well-known to undergo selective complexation with unsaturated compounds. However, such stationary phases often suffer from the loss of chromatographic selectivity as silver(I) ion can be reduced to elemental silver. To maintain the separation performance of silver(I) ion/IL stationary phases, an understanding of factors and conditions that promote the reduction of silver(I) ion is needed. In this study, capillary gas chromatography columns featuring a stationary phase consisting of the 1-decyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C₁₀MIM⁺][NTf₂^-]) IL impregnated with [Ag⁺][NTf₂^-] were examined to investigate the effects of temperature, hydrogen content in exposure gas stream, and time of heating/exposure events on olefin selectivity. Retention factors of representative analytes, such as C₆ olefins and paraffins as well as aromatic compounds, were measured after subjecting the columns to the aforementioned conditions, followed by an evaluation of selectivity factors over time. Selectivity factors of olefins and aromatic compounds were observed to decrease significantly when the stationary phases were heated to temperatures higher than 110°C as well as being subjected to mixed gas streams containing greater than 50 mol% of hydrogen. As constant column heating temperatures were applied under exposure gas mixtures containing hydrogen and nitrogen, a gradual decrease in analyte selectivity factors was observed under prolonged periods of time. However, application of a ternary gas mixture comprised of 25/50/25 mol% hydrogen/nitrogen/methane resulted in an increase in the 3-hexyne/cis-2-hexene selectivity when measured at 120°C for 60 h, due to a smaller decrease in the retention factor of 3-hexyne compared to cis-2-hexene.

The Membrane Interactions of Nano-Silica and Its Potential Application in Animal Nutrition

Simple Summary

Silicon dioxide nanostructures, due to good biocompatibility, low toxicity and high synthetic availability, are promising materials for various biological and industrial applications. Interest in using silicon dioxide nanostructures arises not only from their special interactions with cell membranes, but also from an ease in manipulating their particle size, shape and porosity, allowing one to make a material with the desired physicochemical properties. Despite that, there is still little known about the possible use of silicon dioxide and other nanostructures in animal nutrition. The aim of the present paper was to describe the properties of silica nanostructures, demonstrating potential applications and achievable benefits of using nanostructures as a feed additive. Based on the literature, it seems that diet supplementation with nanoparticles leads to improved performance and immunity in animals, which might be, at least partially, related to changes in the composition of gut microbiota. These unique features make nanoparticles interesting candidates as feed additives used in animal nutrition.

Abstract

Nanoparticles are increasingly popular in numerous fields including electronics, optics and medicine (vaccines, tissue engineering, microsurgery, genomics and cancer therapies). The most widely used nanoparticles in biomedical applications are those designed by man. Scientists have obtained many types of silica nanoparticles with defined shape and chemical composition, but different properties and applications. Nanoparticles include particles with at least one dimension ranging from 1–100 nm. Silica nanoparticles (Sn), reaching values from several dozen to several hundred m²/g, have unique physicochemical properties due to their porous structure and well-developed specific surface. Currently, the use of Sn in animal nutrition, with a focus on gastrointestinal tract function, is of great interest.

Liquid Crystals as Stationary Phases in Chromatography

The most correct analysis of the compositions of diverse analytes mixtures is significant for analytical studies in different fields; however, many prevalent analytes cannot be identified employing traditional partition gas chromatographic methods. Thus, the increasing requirements on analytes of isomeric compounds and the problems encountered in their separation demand a study of more diverse analytical systems which are characterised by higher selectivity. Therefore, the selectivity and polarities of various liquid crystals (rod-like, banana-shape, biforked, oxygen, sulphur, nitrogen, and metal containing molecules, Schiff-base, and polymeric dendrimers) employed as liquid crystalline stationary phases (LCSPs) have been discussed from both points of views, namely, their analytical applications and thermodynamic characteristics of infinitely diluted probes with different acceptor–donor properties. Extreme particular effort has been paid to the different interdependencies between the bound up chemical structures of liquid crystal molecules with their different acceptor–donor properties and the connected resolution capabilities in the interpretation of the probe—LCSP systems, on the basis of the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ { \ln }V_{g\left( T \right)} = f\left( {\frac{1}{T}} \right) $$\end{document}lnVgT=f1T and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ { \ln }\left( {\frac{{a_{1} }}{{w_{1} }}} \right)^{\infty } = f\left( {\frac{1}{T}} \right) $$\end{document}lna1w1∞=f1T dependencies, with regard to the LCSP compositions, which have been controlled by the counterbalancing of the enthalpy and entropy factors. The properties of binary systems composed of liquid crystalline poly(propyleneimine) dendrimers—rod-like molecules of liquid crystals and effects of the dendrimer structure, the chemical nature, and molecular size of the non-mesogens on the ability to dissolve in the liquid crystalline phases, have been interpreted. Practical applications of metallomesogenes and chiral stationary phases for analytical separation of different organic substances have also been taken into consideration.