Extrathermodynamic interpretation of retention equilibria in reversed-phase liquid chromatography using octadecylsilyl-silica gels bonded to C1 and C18 ligands of different densities

Journal Article · Thu Sep 01 00:00:00 EDT 2005 · Journal of Chromatography A

DOI:https://doi.org/10.1016/j.chroma.2005.09.001· OSTI ID:989602

Miyabe, Kanji ^[1]; Guiochon, Georges A ^[2]

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1. Toyama University, Japan
2. ORNL

The retention behavior on silica gels bonded to C{sub 18} and C{sub 1} alkyl ligands of different densities was studied in reversed-phase liquid chromatography (RPLC) from the viewpoints of two extrathermodynamic relationships, enthalpy-entropy compensation (EEC) and linear free energy relationship (LFER). First, the four tests proposed by Krug et al. were applied to the values of the retention equilibrium constants (K) normalized by the alkyl ligand density. These tests showed that a real EEC of the retention equilibrium originates from substantial physico-chemical effects. Second, we derived a new model based on the EEC to explain the LFER between the retention equilibria under different RPLC conditions. The new model indicates how the slope and intercept of the LFER are correlated to the compensation temperatures derived from the EEC analyses and to several parameters characterizing the molecular contributions to the changes in enthalpy and entropy. Finally, we calculated K under various RPLC conditions from only one original experimental K datum by assuming that the contributions of the C{sub 18} and C{sub 1} ligands to K are additive and that their contributions are proportional to the density of each ligand. The estimated K values are in agreement with the corresponding experimental data, demonstrating that our model is useful to explain the variations of K due to changes in the RPLC conditions.

• 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: 989602
• Journal Information: Journal of Chromatography A, Vol. 1099, Issue 2005; ISSN 0021-9673
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
LIQUID COLUMN CHROMATOGRAPHY
ENTHALPY
ENTROPY
FREE ENERGY
SILICA GEL
ORGANIC SILICON COMPOUNDS
PERFORMANCE
EQUILIBRIUM
MATHEMATICAL MODELS
ligand density in RPLC
extrathermodynamic relationship
retention mechanism
reversed phase liquid chromatography