Regularities of the sorption of cycloalkenyl-substituted thiophenes and 2,2′-bithiophenes from water-acetonitrile solutions on hexadecyl silica gel under conditions of high-performance liquid chromatography

Emel’yanova, N. S.; Kurbatova, S. V.; Saifutdinov, B. R.; Yudashkin, A. V.

doi:10.1134/s0036024411080103

Cited by 3 publications

(2 citation statements)

References 6 publications

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“…The acetonitrile molecule contains a hydrophobic methyl group and a highly polar cyanide group; this unique hydrophobic/polar combination results in the capacity to dissolve a wide range of organic compounds. Moreover, these amphiphilic properties render acetonitrile important for heterogeneous catalysis, especially in aqueous media, in which interactions with a metal oxide surface play a key role in partitioning reactants among the various solvent phases. , As acetonitrile is also miscible in water at any ratio, the acetonitrile–water mixture is a commonly used mobile phase in chromatography and is effective in the separation of many chemical and biomolecular species. − …”

Section: Introductionmentioning

confidence: 99%

Influence of High pH on the Organization of Acetonitrile at the Silica/Water Interface Studied by Sum Frequency Generation Spectroscopy

Rehl

Gibbs

2018

Langmuir

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The acetonitrile-water mixture is one of the most commonly used solvents in hydrophilic interaction chromatography, which contains silica as the solid phase. As such, the silica/acetonitrile-water interface plays a large role in the separation of compounds. Varying the pH is one way to influence retention times, particularly of ionizable solutes, yet the influence of high pH is often unpredictable. To determine how the structure of this interface changes with pH, we utilized the surface specific technique sum frequency generation (SFG). Previous SFG studies at neutral pH have suggested the existence of acetonitrile bilayers at the aqueous silica interface even at low acetonitrile mole fractions. Here we find that the SFG signal from 2900 to 3040 cm at the silica/acetonitrile-water interface increased as we adjusted the aqueous pH from near neutral to high values. This increase in signal was attributed to a greater amount of aligned water which is consistent with an increase in silica surface charge at high pH. In contrast, complementary measurements of the silica/acetonitrile-deuterium oxide interface revealed that the acetonitrile methyl mode nearly vanished as the aqueous pH was increased. This loss of methyl mode signal is indicative of a decrease in the number density of acetonitrile molecules at the interface, as orientation analysis indicates no significant change in the net orientation of the outer leaflet of the acetonitrile bilayer over the pH range studied.

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Section: Introductionmentioning

confidence: 99%

Influence of High pH on the Organization of Acetonitrile at the Silica/Water Interface Studied by Sum Frequency Generation Spectroscopy

Rehl

Gibbs

2018

Langmuir

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“…It is known that linear relationships of the medium-property type specific to the primary chromatographic charac teristics often mask the mechanism of processes that occur at the interface and in the bulk solution. [18][19][20][21][22][23] In addition, relationships between the values of changes in enthalpy and entropy of adsorption from solutions pro vide 14-16 important information. These relationships are defined as enthalpy-entropy compensation or thermo dynamic compensation effect.…”

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Medium-property relationships and compensation effect in the adsorption of heteroaromatic compounds from aqueous acetonitrile solutions

Saifutdinov

2014

Russ Chem Bull

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The thermodynamics of the adsorption of heteroaromatic compounds of the 1,3,4 oxadi azole and 1,2,4,5 tetrazine series from aqueous acetonitrile solutions was studied in Henry´s region under the conditions close to equilibrium using the dynamic method. The applicability of the adsorption retention models to the description of medium-property relationships at different temperatures was evaluated. The effect of the composition of the solution on the thermodynamic characteristics of adsorption was studied. The effect of the acetonitrile concen tration on the enthalpy and entropy of adsorption cannot be described by simple plots, since it is determined by the nature of the adsorbate. At the same time, the Gibbs free energy change of adsorption is characterized by a monotonic dependence on the acetonitrile concentration. Linear relationships between changes in the enthalpy and entropy of adsorption of the same substance from water-acetonitrile media of different compositions were established. The char acter of these relationships is determined by the adsorbate nature and explains the dependence of its thermodynamic characteristics of adsorption on the solution composition. The compen sation of the values of enthalpy and entropy changes in a series of the studied adsorbates measured for the constant composition of the solution was discovered. The concentration of acetonitrile significantly affects the character of this compensation.High performance liquid chromatography (HPLC) enjoys wide use today in both the practical analytical chemistry and physicochemical studies aimed at investi gating the chemistry of adsorbent surface and processes at interfaces. 1-3 Success in the separation of mixtures of compounds was achieved due to the application of highly selective adsorbents as stationary phases for HPLC. Among these are chemically modified silicas, porous graphitic carbon, hypercrosslinked polystyrenes, and metal organic frameworks. 4-12 A further development of analytical pos sibilities of HPLC and physicochemical foundations of its application for study of adsorption equilibrium in solu tions is impossible without the progress in the theory of adsorption selectivity found in liquid phase adsorption in Henry´s region. It is also necessary to understand how the structure and properties of all components of a complicat ed heterogeneous system solution-solid affect the ther modynamic characteristics of adsorption (TCA) from so lutions. 13- 16 It is known that among the most important parameters determining the values of TCA from solutions are the com position of the liquid phase and nature of its components. 13 Many works were published in which the influence of the mobile phase composition on retention in HPLC at the same temperature of the column was studied. 1,17 At the same time, the knowledge of dependence of the TCA on the solution composition is needed to predict the position of the adsorption equilibrium and to control adsorption selectivity under variable experimental conditions. It is known that linear relation...

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The adsorption of hetero- and alicyclic thiophene derivatives from water-acetonitrile solutions on the surface of porous graphitic carbon under high-performance liquid chromatography conditions

Saifutdinov

Emel’yanova²,

Kurbatova³

et al. 2012

Russ. J. Phys. Chem.

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Regularities of the sorption of cycloalkenyl-substituted thiophenes and 2,2′-bithiophenes from water-acetonitrile solutions on hexadecyl silica gel under conditions of high-performance liquid chromatography

Cited by 3 publications

References 6 publications

Influence of High pH on the Organization of Acetonitrile at the Silica/Water Interface Studied by Sum Frequency Generation Spectroscopy

Influence of High pH on the Organization of Acetonitrile at the Silica/Water Interface Studied by Sum Frequency Generation Spectroscopy

Medium-property relationships and compensation effect in the adsorption of heteroaromatic compounds from aqueous acetonitrile solutions

The adsorption of hetero- and alicyclic thiophene derivatives from water-acetonitrile solutions on the surface of porous graphitic carbon under high-performance liquid chromatography conditions

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