Chromatographic Framework to Determine the Enantiomer Binding Mechanism on Pepsin Protein Surface

This paper describes sodium chloride salt effects on both dansyl-D,L aminoacid derivatives-pepsin protein surface association and the selectivity process. The thermodynamic functions of this enantiomer association were determined. The variation plots of the enantiomer association data versus the sodium chloride salt concentration (x) in the bulk solvent indicated a change in both the enantiomer-pepsin association and selectivity mechanisms. Enthalpy-entropy compensation confirmed this observation. This study shows the importance of taking into account, the electrostatic interactions and the hydrophobic effect in order to determinate optimum conditions for enantiomeric separation in this chromatographic system.     

Analysis of the Association Process Between a Series of Phenol Derivatives with Two Novel Fluorinated Stationary Phase Using the Cl− Anion as Retention Marker

Summary Lithium chloride (LiCl) effect on the retention process of a phenol derivative series was investigated on two types of fluorinated stationary phase (i.e. a silica grafted with fluorinated linear alkyl chain (L-FSP) and a silica grafted with fluorinated aromatic ring stationary phase (A-FSP)). The results showed that the solute retention is enhanced when the A-FSP was used instead of the L-FSP due to additional – interactions. For the two fluorinated stationary phases (FSPs), the phenol-FSP association process can be divided into two LiCl concentration domains demonstrated that it was important to take into account the adsorbtion of Cl^– anion on the FSPs. As well, enthalpy-entropy compensation revealed that the solute retention mechanism was independent of the solute molecular structure and confirmed a change on the solute retention mechanism at a critical LiCl concentration value around 0.02M.