Peptides liquid-solid adsorption

Modem HPLC separations of peptides now encompass all of the chromatographic modes—liquid-solid adsorption, liquid-liquid partition, ion-exchange and gel permeation chromatography—with the reversed-... 

In this section peptide separation by gel permeation, normal-phase adsorption, ion-exchange, and liquid-solid adsorption HPLC will be considered. Compared to reversed-phase HPLC, these elution modes have attracted considerably less interest for peptide separations. This is due to a number of factors arising from the diverse characteristics of the solutes... 

The ease of incorporating funchonal groups to modify the pSi surface for mass spectrometric application has allowed for the development of a convenient and simple method for enriching the concentration of analytes. This technique, termed DIOS solid-liquid extraction (SLE), uses the property of differential adsorption selectively to capture analytes from a solution containing contaminants that impede MS analysis. Hydrophobically modified DIOS surfaces could be readily used selectively to remove interferences prior to analysis. DIOS S LE simply involves the deposition of a droplet containing analytes onto the chemically modified DIOS surface then, after approximately 3 s, the sample is aspirated with the same pipette. This short-term deposition allows for any molecule with a propensity to be adsorbed onto the surface to attach itself, while any potential hydrophilic contaminants such as salts and buffers will remain in solution, leaving the surface free from such contaminants. The van der Waals interaction between the analyte and surface leads to a selective extraction of the small molecules, while the hydrophilic contaminants such as salts are removed with the droplet. The DIOS analysis of peptides and small molecules from complex matrices is greatly enhanced by differential adsorption [47]. 

Highly polar organocatalysts such as amino acids and peptides are almost insoluble in conventional organic solvents, but they are soluble in ionic liquids. Because of these physical properties, asymmetric syntheses in ionic liquids under biphasic condition have been reported [124], Recently, combinations of solid catalysts and ionic liquids have been studied intensively. The supported ionic liquid phase catalyst is a new generation of the supported liquid-phase catalyst [125]. The supported ionic liquid phase catalyst 232 is readily prepared by adsorption of (S)-proline 13... 

---