Reverse-High Performance Liquid Chromatography Mechanism Explained by Polarization of Stationary Phase

Abstract : Original results and conclusions on Reverse Phase High Performance Liquid Chromatography (RPLC) mechanism are here presented. So far, none of the theoretical approaches applied to the RPLC mechanism can explain the retention and elution mechanisms of most of the analytes by RPLC, especially neutral organic compounds. Our experiences allowed us to state that RPLC reten- tion mechanism most likely occurs through polari-zation of stationary phase (usually dielectric sur-faces) submerged into solvents with huge dielectric constant and high dipole moment (i.e. water and/or acetonitrile) at high pressures as those applied in RPLC systems. The surface polarized interacts with polarizable target analytes (i.e. naphthalene, pyrene or benzo(ghi)perylene) in such a way that the retention depends on the medium polarizability of the target compound. The higher is the medium polarizability of the compound retained the higher is its retention time. By using Polycyclic Aromatic Hydro-carbons (PAHs) and 6-nitrochrysene as probes, we found that although the dependence of retention times on pressure is not evident in most cases, the interac-tion between pressure and the mobile phase dipole moment is evidenced at the light of the constructed mathematical models. Two very different cases can be distinguished: 1. On one hand, when low dipole moment mobile phases are used, high pressure means big work developed by the system in such a way that high pressures inside the system reduce retention times compared to low pressures. 2. On the another one, when high dipole moment solvents are used as mobile phase, high pressure entails an outstanding increase of the retention times compared to low dipole moment mobile phases. This is most likely due to high pressures that entail closer alignment of mobile phase dipoles and lesser tilt of them, originating an outstanding electric field inside the analytical column. In addition to this, reduced retention times for dipole solutes (6-nitrochrysene, dipole molecule) compared to non-polar solutes (PAHs) were ob-served when pressure drops. This conclusions would allow to extend the model to basic/acid molecules at different pH. In this case, electrostatic repulsions among analyte molecules should be considered.
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Contributor : Philippe Dagaut <>
Submitted on : Friday, February 15, 2019 - 10:08:19 AM
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Aurea Andrade-Eiroa, Philippe Dagaut. Reverse-High Performance Liquid Chromatography Mechanism Explained by Polarization of Stationary Phase. Chem-Bio Informatics Journal, Chem-Bio Informatics Society, 2011, 1 (1), pp.62-79. ⟨10.5618/chem.2011.v1.n1.8⟩. ⟨hal-02020218⟩

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