Extension of Toth function from gas-solid to liquid-solid equilibria and application to reversed-phase liquid chromatography systems

Journal Article · Wed Mar 01 00:00:00 EST 2006 · Journal of Colloid and Interface Science

DOI:https://doi.org/10.1016/j.jcis.2006.02.009· OSTI ID:989615

Gritti, Fabrice ^[1]; Guiochon, Georges A ^[2]

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1. University of Tennessee, Knoxville (UTK)
2. ORNL

The extension of the {Psi} function developed by Toth from equilibria taking place at gas-solid interfaces to those taking place at liquid-solid interfaces was investigated. The results were applied to conventional liquid-solid systems used in reversed-phase liquid chromatography (RPLC). The adsorbents in these systems are made of porous silica having a hydrophobic solid surface obtained by chemically bonding C{sub 18} alkyl chains to a porous silica gel then endcapping the surface with trimethylsilyl groups. The liquid is an aqueous solution of an organic solvent, most often methanol or acetonitrile. The probe compound used here is phenol. Adsorption data of phenol were measured using the dynamic frontal analysis (FA) method. The excess adsorption of the organic solvent was measured using the minor disturbance (MD) method. Activity coefficients in the bulk were estimated through the UNIFAC group contributions. The results show that the {Psi} function predicts 90% of the total free energy of immersion, {Delta}F, of the solid when the concentration of phenol is moderate (typically less than 10 g/L). At higher concentrations, the nonideal behavior of the bulk liquid phase becomes significant and it may contribute up to about 30% of {Delta}F. The high concentration of adsorbed molecules of phenol at the interface decreases the interfacial tension, {sigma}, by about 18 mN/m, independently of the structure of the adsorbed phase and of the nature of the organic solvent.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: DE-AC05-00OR22725
• OSTI ID: 989615
• Journal Information: Journal of Colloid and Interface Science, Vol. 299, Issue 2006; ISSN 0021-9797
• Country of Publication: United States
• Language: English

Related Subjects

10 SYNTHETIC FUELS
ACETONITRILE
ADSORBENTS
ADSORPTION
AQUEOUS SOLUTIONS
BONDING
CHAINS
CHROMATOGRAPHY
DISTURBANCES
FREE ENERGY
METHANOL
ORGANIC SOLVENTS
PHENOL
PROBES
REACTION KINETICS
SILICA
SILICA GEL
THERMODYNAMIC ACTIVITY
liquid-solid equilibrium
integral isotherm equations
Gibbs equation
free energy of the surface
reversed-phase liquid chromatography
adsorption isotherms
measured isotherms
frontal analysis
minor disturbance method
methanol-water liquid phase