Journal
JOURNAL OF CHROMATOGRAPHY A
Volume 1611, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.chroma.2019.460594
Keywords
van 't Hoff plot; Entropy change; Enthalpy change; Adsorption sites; Chiral separation mechanism; Thermodynamics
Funding
- NKFIH OTKA [K125312]
- New National Excellence Program of the Ministry of Human Capacities [UNKP-18-3-I-PTE-190]
- European Union
- European Social Fund [EFOP-3.6.1.-16-2016-00004]
- [GINOP-2.3.2-15-2016-00022]
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van 't Hoff plots (logarithm of the retention factor, ink, vs. the reciprocal of absolute temperature, 1/T) are commonly used in chromatographic studies to characterize the retention mechanisms based on the determined enthalpy (Delta H degrees) and entropy (Delta S degrees) change of analyte adsorption. In reversed phase liquid chromatography, the thermodynamic parameters could help to understand the retention mechanism. In chiral chromatography, however, the conclusions drawn based on van 't Hoff plots can be deceptive because several different types of adsorption sites are present on the surface of stationary phase. The influence of heterogeneity, however, cannot be studied experimentally. In this study, we employed two reversed phase columns with different retention mechanisms to show that by serially coupling the columns, the obtained thermodynamic parameters are not related to the results obtained on the respective individual columns. Furthermore, our results show that the experimental conditions - such as flow-rate or choice of instrument - will strongly influence the calculated enthalpy and entropy values. (C) 2019 The Authors. Published by Elsevier B.V.
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