Temperature dependence of solvation heat capacities by gas chromatography

Fekete, Zoltán; Héberger, Károly; Király, Zoltán; Görgényi, Miklós

doi:10.1016/j.aca.2005.06.027

Cited by 8 publications

(3 citation statements)

References 14 publications

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“…It has to be said in fairness that both enthalpy and entropy vary slowly as temperature increases, hence the linear relationship between ln ( K / T ) and 1/ T will approximately hold true within a limited range of temperatures. In order to improve this approximation, it is necessary to substitute enthalpies and entropies in with the following linear equations obtained by disregarding high‐order terms in polynomial expansion of specific heat capacity at constant pressure :

Δ H ≅ Δ H_{0} + Δ H_{1} \cdot T

Δ S ≅ Δ S_{0} + Δ S_{1} \cdot T

where ΔH 0 , Δ H 1 , Δ S 0 , and ΔS 1 remain constant as T varies. After introducing and into and combining constant terms we obtain:

ln K = ln T + \frac{A^{'}}{T} + B^{'} + C^{'} \cdot T

where A ′, B ′, and C ′ are constants, which can be estimated by applying multiple linear regression analysis to the function T · ln ( K / T ) vs. ( T , T 2 ).…”

Section: Optimization Of the Working Temperature Applied To Tandem‐comentioning

confidence: 99%

GC models for separation optimization in pressure-tuneable tandem capillary columns operated isothermally. Part 1: Theoretical aspects

et al. 2013

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GC column selectivity can be continuously adapted to suit analytical needs using a flow-tuneable tandem system. Its application for the separation of complex mixtures requires a deep understanding of the theory in this area. Although a number of researchers have developed specific models, a general and exhaustive theory is still missing. In this paper, we have made an implementation of pre-existing models on tandem-column assemblies operated isothermally. In particular, we have investigated the effect of column length and diameter, phase thickness, and oven temperature on chromatographic parameters, such as capacity factor, selectivity, and intrinsic resolution. A new approach for the correct choice of the working temperature has been proposed.

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Δ H ≅ Δ H_{0} + Δ H_{1} \cdot T

Δ S ≅ Δ S_{0} + Δ S_{1} \cdot T

where ΔH 0 , Δ H 1 , Δ S 0 , and ΔS 1 remain constant as T varies. After introducing and into and combining constant terms we obtain:

ln K = ln T + \frac{A^{'}}{T} + B^{'} + C^{'} \cdot T

where A ′, B ′, and C ′ are constants, which can be estimated by applying multiple linear regression analysis to the function T · ln ( K / T ) vs. ( T , T 2 ).…”

Section: Optimization Of the Working Temperature Applied To Tandem‐comentioning

confidence: 99%

GC models for separation optimization in pressure-tuneable tandem capillary columns operated isothermally. Part 1: Theoretical aspects

et al. 2013

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“…The methods of Mintz et al discussed earlier can be looked upon as the empirical approach to modeling the temperature dependence of the partition coefficient. Recent efforts made by Fekete 262 and Gonzalez 263 have attempted to account for the molecular origins of DC P . The main idea adopted here is to split the contribution to DG o solv into two parts: the first coming from a change in the internal rotations and vibrations of the solute molecule and the second coming from all other terms such as cavity formation and solute-solvent interactions.…”

Section: 21mentioning

confidence: 99%

Predicting solvation energies for kinetic modeling

Jalan

Ashcraft

West

et al. 2010

Annu. Rep. Prog. Chem., Sect. C: Phys. Chem.

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“…It should be noted that the use of ln ( k / T ) instead of ln k in relationships similar to eq can frequently be found in the literature (e.g., Görgényi and Héberger, Fekete et al, Ellison, and Lebrón-Aguilar et al). However, only dimensionless pure numbers have logarithms (see also discussions by Keleti and Zhou and Zhou) while taking the logarithm of a quantity with units (such as k / T ) can provide erroneous Δ solv G i o ( T ) data and should be avoided.…”

Section: Introductionmentioning

confidence: 98%

Estimating Vapor Pressure Data from Gas–Liquid Chromatography Retention Times: Analysis of Multiple Reference Approaches, Review of Prior Applications, and Outlook

et al. 2022

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Reliable methods for determining the vapor pressures of organic materials are of increasing importance as a tool for predicting the behavior and fate of chemicals that are introduced into the environment. In the present work, we analyze the method that relates the gas–liquid chromatography (GLC) retention data, namely, the retention factors (k) of selected organic compounds with their vapor pressures (p 0) using multiple reference standards. Temperature-dependent k values of test chemicals and an adequate number y of reference standard chemicals having directly measured vapor pressure values at temperatures corresponding to GLC measurements are required to apply this method (GLC-RTyS). Retention data of 49 test compounds including a series of alkanes, alkanols, alkyl benzenes, phenols, some (hydro)naphthalene derivatives, and menthol determined on a low-polar dimethylpolysiloxane (HP-1) column at a temperature range from 353 K to (403 or 423) K were used for method validation. We present a first systematic analysis aimed at examining whether and to what extent the selection of experimental conditions might influence/improve the results. Furthermore, we present a review of an alternative multireference correlation gas chromatographic (CGC) method that employs significant extrapolations and is based on the use of adjusted retention time t′ instead of k in order to reveal uncertainties inherent in routine application of this method.

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Temperature dependence of solvation heat capacities by gas chromatography

Cited by 8 publications

References 14 publications

GC models for separation optimization in pressure-tuneable tandem capillary columns operated isothermally. Part 1: Theoretical aspects

GC models for separation optimization in pressure-tuneable tandem capillary columns operated isothermally. Part 1: Theoretical aspects

Predicting solvation energies for kinetic modeling

Estimating Vapor Pressure Data from Gas–Liquid Chromatography Retention Times: Analysis of Multiple Reference Approaches, Review of Prior Applications, and Outlook

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