On the discrepancy between crossovers of solubility in supercritical carbon dioxide and retention in supercritical fluid chromatography.

Various crossover phenomena are immanent to supercritical fluids due to multidirectional temperature effects in highly compressible supercritical fluid media. Solubility crossover, i.e.

Understanding Complex Interplay among Different Instabilities in Multiferroic BiMnO Using Fe Probe Mössbauer Spectroscopy.

Here, we report the results of a Mössbauer study on hyperfine electrical and magnetic interactions in quadruple perovskite BiMnO doped with Fe probes. Measurements were performed in the temperature range of 10 K < < 670 K, wherein BiMnFeO undergoes a cascade of structural ( ≈ 590 K, ≈ 442 K, and ≈ 240 K) and magnetic ( ≈ 57 K, ≈ 50 K, and ≈ 24 K) phase transitions. The analysis of the electric field gradient (EFG) parameters, including the dipole contribution from Bi ions, confirmed the presence of the local dipole moments , which are randomly oriented in the paraelectric cubic phase ( > ).

Poly(vinyl chloride)/Nanocarbon Composites for Advanced Potentiometric Membrane Sensor Design.

Polymer nanocomposites filled with carbon nanoparticles (CNPs) are a hot topic in materials science. This article discusses the current research on the use of these materials as interfacial electron transfer films for solid contact potentiometric membrane sensors (SC-PMSs). The results of a comparative study of plasticized poly (vinyl chloride) (pPVC) matrices modified with single-walled carbon nanotubes (SWCNTs), fullerenes-C60, and their hybrid ensemble (SWCNTs-C60) are reported.

Entropy driven separation of xylene isomers on graphitic carbon adsorbents.

Separation of xylene isomers remains one of the most important and challenging applications of adsorption-based separations in petrochemical industry. Despite the sustainable success of zeolite-based separations a search for efficient adsorbents selective for xylenes, especially para-xylene, is constantly ongoing. In this work, a potentially scalable chromatographic separation of all three xylenes was achieved on graphitic carbon sorbents, including a self-packed sorbent based on an oligo-graphene.

Nafion-212 Membrane Solvated by Ethylene and Propylene Carbonates as Electrolyte for Lithium Metal Batteries.

The use of cation-exchange membranes as electrolytes for lithium metal batteries can prevent the formation of lithium dendrites during extended cycling and guarantee safe battery operation. In our study, the Nafion-212 membrane in lithium form solvated by a mixture of ethylene carbonate and propylene carbonate (EC-PC) was used as an electrolyte in a lithium metal battery with the LiFePO cathode. The Nafion-212-EC-PC electrolyte is electrochemically stable up to 6 V, indicating its suitability for high-energy density batteries.

Chromatography-like propagation of water along raw material bed in supercritical fluid extraction.

A chromatography-like propagation of water through the material bed was observed while performing supercritical fluid extraction of aroma plants having high moisture content. While parts of raw material bed placed at the inlet of the extraction vessel get dried after appropriate extraction time, the parts closer to the outlet not only stay wet but, in fact, gain more moisture than initial raw material. Presumably, water and other extractables with limited solubility in supercritical CO, get re-adsorbed onto the plant material surface along the extraction column and then desorbed further on.

[Antiviral properties of synthetic histidine derivatives containing membranotropic volumetrical carbocycles in their molecule against SARS-CoV-2 virus ].

Introduction: Currently, low molecular-weight compounds are being developed as potential inhibitors of CoVs replication, targeting various stages of the replication cycle, such as major protease inhibitors and nucleoside analogs. Viroporins can be alternative protein targets. The aim of this study is to identify antiviral properties of histidine derivatives with cage substituents in relation to pandemic strain SARS-CoV-2 in vitro.

Study of Lithium-Extraction Systems Based on Benzo-15-Crown-5 Ether and Alkylimidazolium-Based Ionic Liquid.

The extraction of lithium from aqueous solutions of LiNTf and LiCl salts using benzo-15-crown-5 ether (B15C5) as an extractant in [C8mim][NTf] ionic liquid was studied. The transition of the extractant into the aqueous phase and the distribution of Cl ions during lithium extraction from LiCl solutions were determined. LiNTf complexes with B15C5 with different LiNTf:B15C5 ratios were isolated for the first time and characterized via X-ray diffraction and IR spectroscopy.

Synthesis and Self-Assembly of β-Octa[(4-Diethoxyphosphoryl)phenyl]porphyrins.

The β-substituted porphyrinoids commonly used to form functional assembled systems in nature yet are still scarcely used in material chemistry probably due to the laborious synthesis of these compounds. In this work, β-octa[(4-diethoxyphosphoryl)phenyl]porphyrin () and its metal (Zn(II), Cd(II), Cu(II), and Ni(II)) complexes were prepared in good yields. These highly soluble chromophores were characterized in solution using spectroscopic (NMR, UV-vis, fluorescence), electrochemical, and spectroelectrochemical methods.

Carbon-atom hybridization tunes the halogen-bond strength in the series of DABCO·CHI (n = 0-2) cocrystals.

Two new cocrystals of 1,4-diazabicyclo[2.2.2]octane (DABCO, CHN) with 1,2-diiodoethene (1,2-CHI) and 1,2-diiodoethane (1,2-CHI) complete a series of halogen-bond-assisted cocrystals which started with DABCO·CI [Perkins et al.

Retention mechanisms of imidazoline and piperazine-related compounds in non-aqueous hydrophilic interaction and supercritical fluid chromatography based on chemometric design and analysis.

The experimental design methodology based on central composite design of experiments was applied to compare the retention mechanisms in supercritical fluid chromatography (SFC) and non-aqueous hydrophilic interaction liquid chromatography (NA-HILIC). The selected set consists of 26 compounds that belong to imidazoline and serotonin receptor ligands. The different chemometric tools (multiple linear regression, principal component analysis, parallel factor analysis) were used to examine the retention, as well as to identify the most significant retention mechanisms.

A New Approach to the Formation of Nanosized Gold and Beryllium Films by Ion-Beam Sputtering Deposition.

Thin films of beryllium and gold that are several tens of nanometers thick were obtained, for the first time, on silicon and quartz substrates by the ion-beam method with tenfold alternation of deposition and partial sputtering of the nanosized metal layer. Scanning electron and atomic force microscopy indicate the predominant lateral growth of nanosized metal layers along the substrate surface. Optical spectra indicate the suppression of the localized plasmon resonance.

Potentiometric quantitation of general local anesthetics with a new highly sensitive membrane sensor.

The detection of local anesthetic drugs is of great importance in the analysis of pharmaceutical, clinical and forensic samples. This paper reports a simple and sensitive potentiometric assay suitable for detecting general local anesthetics (LAs) of two types, namely: amino ester-anesthetics (procaine) and amino amide-anesthetics (lidocaine, articaine). As a detector, a new highly sensitive sensor based on a poly(vinyl chloride)-matrix membrane incorporating ion-pair complexes of protonated procaine with 2-[bis-octadecyl-sulfonic)-closo-decaborate is used.

Some aspects of additives effects on retention in supercritical fluid chromatography studied by linear free energy relationships method.

This work is dedicated to the investigation of additives effects on retention mechanisms in supercritical fluid chromatography. Additives are compounds which are added to the mobile phase in small quantities and greatly affect retention factors, peak shape, separation selectivity and other chromatographic parameters. Linear free energy relationship (LFER) method with an expanded set of descriptors including the ones taking ionic interactions into account was used to probe the effect of four types of additive: trifluoroacetic acid, diethylamine, ammonium acetate and water - on retention on four polar stationary phase bearing different functional groups: bare silica, cyano, 2-ethylpyridine and zwitter-ionic sulfobetaine.

Octopus-Type Crown-Bisphthalocyaninate Anchor for Bottom-Up Assembly of Supramolecular Bilayers with Expanded Redox-Switching Capability.

Achievement of information storage at molecular level remains a pressing task in miniaturization of computing technology. One of the promising approaches for its practical realization is development of nanoscale molecular switching materials including redox-active systems. The present work demonstrates a concept of expansion of a number of available redox-states of self-assembled monolayers through supramolecular approach.

Chimeric supramolecular synthons in PhTe(I)Se.

Iodination of PhTeSe by molecular iodine is directed towards the Te atom and yields {diiodo[(phenyltellanyl)selanyl]-λ-tellanyl}benzene, PhTeSeTeIPh or CHISeTe. The molecule can be considered as a chimera of PhTeSeR, PhTeSeTePh and R'TeIPh fragments. The crystal structure features a complex interplay of the supramolecular synthons Te.

On the Enhanced Accuracy of Kinetic Curve Building in Supercritical Fluid Extraction from Aroma Plants Using a New 3D-Printed Extract Collection Device.

Accurate collection of extracted material represents a technical problem in supercritical fluid extraction because trapping should be performed in severe conditions of rapidly moving and freezing expanded fluid. We have developed a simple device for effective sample collection in analytical-scale supercritical fluid extraction. The device consists of a cyclone separator equipped with a spray trap and a heated check valve.

Long-Sought Redox Isomerization of the Europium(III/II) Complex Achieved by Molecular Reorientation at the Interface.

Redox isomerism, that is, the change of a metal cation valence state in organic complexes, can find promising applications in multistable molecular switches for various molecular electronic devices. However, despite a large number of studies devoted to such processes in organic complexes of multivalent lanthanides, redox-isomeric transformations were never observed for europium. In the present work, we demonstrate the unique case of redox isomerization of Eu(III)/Eu(II) complexes on the example of Eu double-decker octa--butoxyphthalocyaninate () under ambient conditions (air and room temperature).

Polymer Electrolytes for LIBs Based on Perfluorinated Sulfocationic Nepem-117 Membrane and Aprotic Solvents.

Polymer electrolytes have been obtained by using Nepem-117 membranes in a Li form intercalated by polar aprotic solvents, such as dimethylformamide, dimethyl sulfoxide (DMSO), and dimethylacetamide (DMA), and solvent mixtures, such as ethylene carbonate-propylene carbonate (EC-PC), EC-DMA, EC-PC-DMA, and EC-PC-DMA-tetrahydrofuran. The obtained electrolytes have been characterized by IR impedance and Li pulsed field gradient NMR spectroscopy. Ion mobility was observed to increase with higher degrees of solvation of the membranes.

Unusual effect of flow rate on retention in analytical supercritical fluid chromatography exemplified by polyethylene glycol separation.

We report a case of a peculiar effect of flow rate on retention in a separation of polyethylene glycol oligomers via supercritical fluid chromatography. During method development, we tested flow rate gradients and notices that for some PEG oligomers retention times at flow rate gradient were lower than at constant flow with the largest flow rate value used in a gradient. For instance, at BEH stationary phase and CO-MeOH gradient from 10 to 35% at 20 min a PEG oligomer having mass of 1225 Da has a retention time 14 min at 1 mL/min flow rate, 10.

Flexible Polycaprolactone and Polycaprolactone/Graphene Scaffolds for Tissue Engineering.

Developing bone scaffolds can greatly improve the patient's quality of life by accelerating the rehabilitation process. In this paper, we studied the process of composite polycaprolactone supercritical foaming for tissue engineering. The influence of graphene oxide and reduced graphene oxide on the foaming parameters was studied.

High-temperature resistive gas sensors based on ZnO/SiC nanocomposites.

Increasing requirements for environmental protection have led to the need for the development of control systems for exhaust gases monitored directly at high temperatures in the range of 300-800 °C. The development of high-temperature gas sensors requires the creation of new materials that are stable under these conditions. The stability of nanostructured semiconductor oxides at high temperature can be enhanced by creating composites with highly dispersed silicon carbide (SiC).

Unexpected separate elution of cation and anion of an ammonium salt in supercritical fluid chromatography.

Amines are frequently used as additives in supercritical fluid chromatography (SFC). They allow eluting basic analytes with reasonable retention times and less distorted peak shapes. Since amines are chemically active compounds, their introduction into SFC mobile phase always raises a question on whether they can react with analytes or mobile phase constituents and, if so, can it affect chromatography separation.

Effects of Ag Additive in Low Temperature CO Detection with In₂O₃ Based Gas Sensors.

Nanocomposites In₂O₃/Ag obtained by ultraviolet (UV) photoreduction and impregnation methods were studied as materials for CO sensors operating in the temperature range 25⁻250 °C. Nanocrystalline In₂O₃ and In₂O₃/Ag nanocomposites were characterized by X-ray diffraction (XRD), single-point Brunauer-Emmet-Teller (BET) method, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) with energy dispersive X-ray (EDX) mapping. The active surface sites were investigated using Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR) spectroscopy and thermo-programmed reduction with hydrogen (TPR-H₂) method.