An insight into possibility of chemical reaction between dense carbon dioxide and methanol

Oparin, R. D.; Krest’yaninov, М. А.; Vorobyev, E.; Pokrovskiy, O. I.; Паренаго, О. О.; Киселев, М. Г.

doi:10.1016/j.molliq.2016.12.027

Cited by 15 publications

(3 citation statements)

References 32 publications

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“…It is known in the SFC field that supercritical CO 2 (scCO 2 ) combined with methanol (MeOH) modifier has a mildly acidic behavior. This has been confirmed by spectroscopic monitoring of several colorimetric pH indicators. , For alcohol/CO 2 mixtures, this acidity (apparent pH around 5) is believed to be the result of alkylcarbonate or dimethylcarbonate formation at high pressures. Lindner et al suggested that there was evidence of transient acid species formation as evidenced by the ion-exchange mechanism when introducing ammonia and amine-based additives for chiral separation purposes. − In particular, methylcarbonate formed in situ from the presence of methanol with compressed CO 2 and carbamates could form from the addition of primary and secondary amines to that solvent system.…”

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confidence: 75%

“…This has been confirmed by spectroscopic monitoring of several colorimetric pH indicators. 11,38 For alcohol/CO 2 mixtures, this acidity (apparent pH around 5) is believed to be the result of alkylcarbonate or dimethylcarbonate formation at high pressures. Lindner et al suggested that there was evidence of transient acid species formation as evidenced by the ionexchange mechanism when introducing ammonia and aminebased additives for chiral separation purposes.…”

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confidence: 99%

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Chaotropic Effects in Sub/Supercritical Fluid Chromatography via Ammonium Hydroxide in Water-Rich Modifiers: Enabling Separation of Peptides and Highly Polar Pharmaceuticals at the Preparative Scale

et al. 2019

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Chromatographic separation, analysis and characterization of complex highly polar analyte mixtures can often be very challenging using conventional separation approaches. Analysis and purification of hydrophilic compounds have been dominated by liquid chromatography (LC) and ion-exchange chromatography (IC), with sub/supercritical fluid chromatography (SFC) moving toward these new applications beyond traditional chiral separations. However, the low polarity of supercritical carbon dioxide (CO2) has limited the use of SFC for separation and purification in the bioanalytical space, especially at the preparative scale. Reaction mixtures of highly polar species are strongly retained even using polar additives in alcohol modifier/CO2 based eluents. Herein, we overcome these problems by introducing chaotropic effects in SFC separations using a nontraditional mobile phase mixture consisting of ammonium hydroxide combined with high water concentration in the alcohol modifier and carbon dioxide. The separation mechanism was here elucidated based on extensive IC-CD (IC couple to conductivity detection) analysis of cyclic peptides subjected to the SFC conditions, indicating the in situ formation of a bicarbonate counterion (HCO3 –). In contrast to other salts, HCO3 – was found to play a crucial role acting as a chaotropic agent that disrupts undesired H-bonding interactions, which was demonstrated by size-exclusion chromatography coupled with differential hydrogen–deuterium exchange-mass spectrometry experiments (SEC-HDX-MS). In addition, the use of NH4OH in water-rich MeOH modifiers was compared to other commonly used basic additives (diethylamine, triethylamine, and isobutylamine) showing unmatched chromatographic and MS detection performance in terms of peak shape, retention, selectivity, and ionization as well as a completely different selectivity and retention behavior. Moreover, relative to ammonium formate and ammonium acetate in water-rich methanol modifier, the ammonium hydroxide in water additive showed better chromatographic performance with enhanced sensitivity. Further optimization of NH4OH and H2O levels in conjunction with MeOH/CO2 served to furnish a generic modifier (0.2% NH4OH, 5% H2O in MeOH) that enables the widespread transition of SFC to domains that were previously considered out of its scope. This approach is extensively applied to the separation, analysis, and purification of multicomponent reaction mixtures of closely related polar pharmaceuticals using readily available SFC instrumentation. The examples described here cover a broad spectrum of bioanalytical and pharmaceutical applications including analytical and preparative chromatography of organohalogenated species, nucleobases, nucleosides, nucleotides, sulfonamides, and cyclic peptides among other highly polar species.

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Chaotropic Effects in Sub/Supercritical Fluid Chromatography via Ammonium Hydroxide in Water-Rich Modifiers: Enabling Separation of Peptides and Highly Polar Pharmaceuticals at the Preparative Scale

et al. 2019

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“…The growth of fluctuations increase the diffusion inside the media and can also enhance the rate of multiple chemical reactions or increase their efficiency [50]. However, the applied model does not describe the possible chemical reaction between the components, similarly to the chemical reaction between supercritical methanol and carbon dioxide on the inner surface of the cell [51]. The three observed Widom regions are expected to exist for several mixtures of linear molecules.…”

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confidence: 99%

The Anomalous Behavior of Thermodynamic Parameters in the Three Widom Deltas of Carbon Dioxide-Ethanol Mixture

Mareev

Sviridov

Gordienko

2021

IJMS

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Using molecular dynamics, we demonstrated that in the mixture of carbon dioxide and ethanol (25% molar fraction) there are three pronounced regions on the p-T diagram characterized by not only high-density fluctuations but also anomalous behavior of thermodynamic parameters. The regions are interpreted as Widom deltas. The regions were identified as a result of analyzing the dependences of density, density fluctuations, isobaric thermal conductivity, and clustering of a mixture of carbon dioxide and ethanol in a wide range of pressures and temperatures. Two of the regions correspond to the Widom delta for pure supercritical carbon dioxide and ethanol, while the third region is in the immediate vicinity of the critical point of the binary mixture. The origin of these Widom deltas is a result of the large mixed linear clusters formation.

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Effect of the type and concentration of mobile phase additives on the separation of salbutamol sulfate enantiomers in supercritical fluid chromatography

et al. 2018

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An insight into possibility of chemical reaction between dense carbon dioxide and methanol

Cited by 15 publications

References 32 publications

Chaotropic Effects in Sub/Supercritical Fluid Chromatography via Ammonium Hydroxide in Water-Rich Modifiers: Enabling Separation of Peptides and Highly Polar Pharmaceuticals at the Preparative Scale

Chaotropic Effects in Sub/Supercritical Fluid Chromatography via Ammonium Hydroxide in Water-Rich Modifiers: Enabling Separation of Peptides and Highly Polar Pharmaceuticals at the Preparative Scale

The Anomalous Behavior of Thermodynamic Parameters in the Three Widom Deltas of Carbon Dioxide-Ethanol Mixture

Effect of the type and concentration of mobile phase additives on the separation of salbutamol sulfate enantiomers in supercritical fluid chromatography

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