Effect of the temperature on the isotherm parameters of phenol in reversed-phase liquid chromatography

Kim, Hyun-Jung; Gritti, Fabrice; Guiochon, Georges

doi:10.1016/j.chroma.2004.08.025

Cited by 21 publications

(4 citation statements)

References 30 publications

(49 reference statements)

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“…Finally, the total saturation capacity of the Sunfire column decreases by a factor 3 in the temperature range studied, confirming the result observed previously with a Symmetry-C 18 column . This is an important result for preparative chromatography, a field of application in which a high column capacity is useful.…”

Section: Resultssupporting

confidence: 88%

“…How do the saturation capacities and the equilibrium constants of adsorbates change with increasing temperature? A similar study was done earlier on an end-capped C 18 -bonded column (Symmetry, Waters) . It showed that the adsorption of phenol followed a two-site, bi-Langmuir isotherm model behavior and that the number of the low-adsorption energy sites q S,1 and the equilibrium constant of the high-adsorption sites b 2 decrease rapidly while the number of high-adsorption energy sites q S,2 and the equilibrium constant of the low-adsorption energy sites b 1 remain nearly constant when the temperature increases.…”

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confidence: 65%

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Adsorption Mechanisms and Effect of Temperature in Reversed-Phase Liquid Chromatography. Meaning of the Classical Van't Hoff Plot in Chromatography

Gritti

Guiochon

2006

Anal. Chem.

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The effect of temperature on the adsorption and retention behaviors of a low molecular weight compound (phenol) on a C18-bonded silica column (C18-Sunfire, Waters) from aqueous solutions of methanol (20%) or acetonitrile (15%) was investigated. The results of the measurements were interpreted successively on the basis of the linear (i.e., overall retention factors) and the nonlinear (i.e., adsorption isotherms, surface heterogeneity, saturation capacities, and equilibrium constants) chromatographic methods. The confrontation of these two approaches confirmed the impossibility of a sound physical interpretation of the conventional Van't Hoff plot. The classical linear chromatography theory assumes that retention is determined by the equilibrium thermodynamics of analytes between a homogeneous stationary phase and a homogeneous mobile phase (although there may be two or several types of interactions). From values of the experimental retention factors in a temperature interval and estimates of the activity coefficients at infinite dilution in the same temperature interval provided by the UNIFAC group contribution method, evidence is provided that such a retention model cannot hold. The classical Van't Hoff plot appears meaningless and its linear behavior a mere accident. Results from nonlinear chromatography confirm these conclusions and provide explanations. The retention factors seem to fulfill the Van't Hoff equation, not the Henry constants corresponding to the different types of adsorption sites. The saturation capacities and the adsorption energies are clearly temperature dependent. The temperature dependence of these characteristics of the different assorption sites are different in aqueous methanol and acetonitrile solutions.

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Section: Resultssupporting

confidence: 88%

supporting

confidence: 65%

Adsorption Mechanisms and Effect of Temperature in Reversed-Phase Liquid Chromatography. Meaning of the Classical Van't Hoff Plot in Chromatography

Gritti

Guiochon

2006

Anal. Chem.

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“…The effect of the experimental parameters on the nature and on the parameters of the adsorption isotherm has gained some attention. The effects of the temperature, − the pressure, − the ionic strength of the liquid phase, − the presence of a buffer, the nature and concentration of the buffer, , and the quantity of organic modifier present in aqueous mobile phases − were quantified by measuring adsorption data by frontal analysis (FA), following a systematic protocol. These studies have provided new and often unsuspected information regarding the fundamental role played by those parameters on the adsorption process.…”

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confidence: 99%

Adsorption Mechanism in RPLC. Effect of the Nature of the Organic Modifier

2005

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The adsorption isotherms of phenol and caffeine were acquired by frontal analysis on two different adsorbents, Kromasil-C 18 and Discovery-C 18 , with two different mobile phases, aqueous solutions of methanol (MeOH/H 2 O ) 40/60 and 30/70, v/v) and aqueous solutions of acetonitrile (MeCN/H 2 O ) 30/70 and 20/80, v/v). The adsorption isotherms are always strictly convex upward in methanol/water solutions. The calculations of the adsorption energy distribution confirm that the adsorption data for phenol are best modeled with the bi-Langmuir and the tri-Langmuir isotherm models for Kromasil-C 18 and Discovery-C 18 , respectively. Because its molecule is larger and excluded from the deepest sites buried in the bonded layer, the adsorption data of caffeine follow biLangmuir isotherm model behavior on both adsorbents. In contrast, with acetonitrile/water solutions, the adsorption data of both phenol and caffeine deviate far less from linear behavior. They were best modeled by the sum of a Langmuir and a BET isotherm models. The Langmuir term represents the adsorption of the analyte on the highenergy sites located within the C 18 layers and the BET term its adsorption on the low-energy sites and its accumulation in an adsorbed multilayer system of acetonitrile on the bonded alkyl chains. The formation of a complex adsorbed phase containing up to four layers of acetonitrile (with a thickness of 3.4 Å each) was confirmed by the excess adsorption isotherm data measured for acetonitrile on Discovery-C 18 . A simple interpretation of this change in the isotherm curvature at high concentrations when methanol is replaced with acetonitrile as the organic modifier is proposed, based on the structure of the interface between the C 18 chains and the bulk mobile phase. This new model accounts for all the experimental observations.Most chemical analyses, impurity detections, separations, and sample preparations are now performed by using RPLC techniques. The number of experimental parameters the analyst can adjust in order to achieve his goal is important. The degree of hydrophocicity of the RPLC column (length of the alkyl bonded chains attached to the solid support, density of these ligands on the surface, nature of the solid support), the temperature, the pressure, the composition of the mobile phase, and the elution mode (isocratic or gradient) are all experimental parameters that can be easily modified. To predict the analytical elution times or the shape of overloaded band profiles for single-component and multicomponent systems, it is crucial to be able to determine the adsorption equilibria (single and competitive isotherms) of the compounds between the mobile and stationary phases. 1 The effect of the experimental parameters on the nature and on the parameters of the adsorption isotherm has gained some attention. The effects of the temperature, 2-4 the pressure, 5-7 the ionic strength of the liquid phase, 8-11 the presence of a buffer, 12 the nature and concentration of the buffer, 13,14 and the quantity of organic modifie...

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“…The presence of such interactions was confirmed in literature [13] for many silica based (and not only) adsorbents, mobile phases and chromatographed compounds. Besides, in accordance to Kim [14] , qualitative assessments of the adsorption energy distribution (AED) at different temperatures indicate that temperature has a significant influence on the adsorption energy on the high-energy sites and on the saturation capacity of the low-energy sites. The previous investigations of AED [15] conducted in the same column for CAF in different MeOH-water systems, indicate that in the RPLC mode the adsorption mechanism is seriously heterogeneous.…”

Section: Sustainable Chemical Engineeringmentioning

confidence: 69%

Influence of mobile phase composition and temperature on the retention behavior of selected test substances in diol-type column

Zapała

Ziobrowski

Zapała

et al. 2020

SCE

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In this work the effect of mobile phase composition and temperature on the retention behavior of several test compounds (including non-polar and polar substances) on diol-Acclaim Mixed Mode HILIC-1 column in methanol-water systems with high (RPLC mode) and low (HILIC mode) water content was analyzed. In the studied systems both linear, slightly curved and curved van’t Hoff plots were observed. This indicates, that depending on solute physicochemical properties and mobile phase composition, both single and more complex retention mechanism(s) may influence the retention behavior of tested substances. The possibilities of different retention mechanisms existence (e.g. connected with adsorbent surface heterogeneity, hydrophobic and hydrogen bond interactions) in the analyzed systems have been also discussed.

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Effect of the temperature on the isotherm parameters of phenol in reversed-phase liquid chromatography

Cited by 21 publications

References 30 publications

Adsorption Mechanisms and Effect of Temperature in Reversed-Phase Liquid Chromatography. Meaning of the Classical Van't Hoff Plot in Chromatography

Adsorption Mechanisms and Effect of Temperature in Reversed-Phase Liquid Chromatography. Meaning of the Classical Van't Hoff Plot in Chromatography

Adsorption Mechanism in RPLC. Effect of the Nature of the Organic Modifier

Influence of mobile phase composition and temperature on the retention behavior of selected test substances in diol-type column

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