The Determination of Group Contributions to Activity Coefficients by Gas-Liquid Chromatography through Homologous Trends

Scheller, William A.; Petricek, J. L.; Young, Grant M.

doi:10.1021/i160041a009

Cited by 11 publications

(3 citation statements)

References 4 publications

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“…In the literature, numerous data are found in hexadecane as solvent. [21][22][23][24][25] Data at 25 °C, determined with special care, have been published recently by the research group of Carr. 26 With hexadecane as the stationary phase, gas chromatographic data have been determined by using hexadecane-saturated helium as eluent.…”

Section: Theoretical Sectionmentioning

confidence: 99%

“…Let us control the quality of such doubly extrapolated data by comparing them with experimental partition coefficients determined at room temperature in a paraffin of not too low molecular weight. In the literature, numerous data are found in hexadecane as solvent. − Data at 25 °C, determined with special care, have been published recently by the research group of Carr . With hexadecane as the stationary phase, gas chromatographic data have been determined by using hexadecane-saturated helium as eluent.…”

Section: Theoretical Sectionmentioning

confidence: 99%

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Prediction of Activity Coefficients in Low-Molecular-Weight Paraffins from Gas Chromatographic Data

Dallos¹,

Kováts²

1999

Anal. Chem.

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It is shown that gas-liquid partition coefficients measured by gas chromatography on nonvolatile paraffin stationary phases at high temperatures allow estimation of gasliquid partition coefficients of solutes at ambient temperatures in volatile alkanes as solvents. Extrapolation to low temperatures was successful by use of the Kirchhoff equation for the description of the temperature dependence of the standard chemical potential of the solute related to its molal Henry coefficient. A new equation is proposed for the prediction of partition data in lowmolecular-weight paraffins. It was derived by using the Flory-Huggins model as a guide, and it combines theory with experiment. It is proposed to accept a combinatorial entropy term determined by experiment as a solute property. The necessary experimental information consists of a set of gas chromatographic data measured at at least four temperatures on two pure, high-molecularweight paraffins. Molal Henry coefficients extrapolated to low-molecular-weight solvents allowed calculation of activity coefficients. Predicted and measured data agreed within ( 20%. The reproducibility of activity coefficients by classical experimental methods is of the same order of magnitude.Properly designed gas liquid chromatographic experiments permit a rapid collection of accurate gas/liquid partition data at ideal dilution. 1,2 In the chromatographic column the high-molecular-weight solvent (the stationary liquid) is disposed of as a thin film on a support. Therefore, its specific surface area is high, typically of the order of some 5 m 2 g -1 (corresponding to a film thickness of 0.2 µm). Hence, already weak adsorption at the liquid/solid (liquid/support) and the gas/liquid interfaces shall influence the measurement and will result in wrong partition data. By the use of an "inactive support", adsorption at the liquid/ support interface can be eliminated. Adsorption at the liquid/gas interface is roughly proportional to the surface tension of the solvent. 3-5 It cannot be eliminated but can be reduced to a minimum by the adequate choice of solvent and by the use of highly loaded stationary phases, i.e., by reducing the specific surface area of the solvent.Partition data of a solute, j, in a given solvent, sv, as a function of temperature are best presented by calculating the corresponding standard chemical potential, ∆µ j,sv (i.e., the partial molar standard Gibbs free energy). 6Here, κ j,sv , is a partial pressure (fugacity) characterizing partition, R is the universal gas constant, T is the thermodynamic temperature, and the symbols ∆H j,sv (T) and ∆S j,sv (T) are for the partial molar enthalpy and entropy differences of the solute between the ideal gas phase and the ideal dilute solution. The relationship of eq 1 shows that the standard chemical potential difference depends both on specific enthalpic interactions between solute and solvent (attraction due to polarity, hydrogen bonding, etc.) and on the entropy. The latter also includes the so-called combinatorial entropy: contributi...

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Section: Theoretical Sectionmentioning

confidence: 99%

Section: Theoretical Sectionmentioning

confidence: 99%

Prediction of Activity Coefficients in Low-Molecular-Weight Paraffins from Gas Chromatographic Data

Dallos¹,

Kováts²

1999

Anal. Chem.

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“…Activity coefficients at extreme dilution were measured by Popescu et al (687) by using solvent mixtures as stationary phases. A method was described for the determination of group contributions to activity coefficients through homologous series trends (752). Hussey and Parcher (404) applied a modified Wilson's equation for excess free energy to a number of chromatographic systems and showed that a single limiting activity coefficient may be used to predict the compositional dependence of the activity coefficient.…”

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confidence: 99%

Gas chromatography

Juvet¹,

Cram²

1974

Anal. Chem.

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This review surveys developments in the field of gas chromatography since publication of the last review in this series (178) and covers the years 1972-73. Gas chromatography continues to be one of the most active areas in analytical chemistry. In the 1973 Directory of Membership of the ACS Division of Analytical Chemistry (356), those listing their research specialty as "gas chromatography" were second in numbers only to those listing the drugs compiled by the editorial staff (423) and articles on applications of GC in alcohol analysis (417), hallucinogenic drugs ( 818), the analysis of narcotic analgesics and amphetamines (622), barbiturates (446), and phenothiazine drugs (158).

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Thermodynamic properties of binary mixtures containing ketones. VI. Analysis of the properties of 2-propanone + n-alkane mixtures in terms of a quasi-chemical group contribution model

Kehiaian

Grolier

Kechavarz³

et al. 1981

Fluid Phase Equilibria

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The Determination of Group Contributions to Activity Coefficients by Gas-Liquid Chromatography through Homologous Trends

Cited by 11 publications

References 4 publications

Prediction of Activity Coefficients in Low-Molecular-Weight Paraffins from Gas Chromatographic Data

Prediction of Activity Coefficients in Low-Molecular-Weight Paraffins from Gas Chromatographic Data

Gas chromatography

Thermodynamic properties of binary mixtures containing ketones. VI. Analysis of the properties of 2-propanone + n-alkane mixtures in terms of a quasi-chemical group contribution model

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