Pi-selective stationary phases: (II) Adsorption behaviour of substituted aromatic compounds on n-alkyl-phenyl stationary phases.
The frontal analysis method was used to measure the adsorption isotherms of phenol, 4-chlorophenol, p-cresol, 4-methoxyphenol and caffeine on a series of columns packed with home-made alkyl-phenyl bonded silica particles. These ligands consist of a phenyl ring tethered to the silica support via a carbon chain of length ranging from 0 to 4 atoms. The adsorption isotherm models that fit best to the data account for solute-solute interactions that are likely caused by pi-pi interactions occurring between aromatic compounds and the phenyl group of the ligand. These interactions are the dominant factor responsible for the separation of low molecular weight aromatic compounds on these phenyl-type stationary phases. The saturation capacities depend on whether the spacer of the ligands have an even or an odd number of carbon atoms, with the even alkyl chain lengths having a greater saturation capacity than the odd alkyl chain lengths. The trends in the adsorption equilibrium constant are also significantly different for the even and the odd chain length ligands.
Australian Centre for Research on Separation Science, School of Natural Sciences, University of Western Sydney Node, Parramatta, NSW, Australia.
Paul G
PG
Stevenson
Fabrice
F
Gritti
Georges
G
Guiochon
Kirsty J
KJ
Mayfield
Gary R
GR
Dennis
R Andrew
RA
Shalliker
D000327:Adsorption; D000465:Algorithms; D002110:Caffeine / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D008956:Models, Chemical; D008968:Molecular Conformation; D008970:Molecular Weight; D010636:Phenols / Q000737:chemistry*; D012044:Regression Analysis; D013696:Temperature
D010636:Phenols; D002110:Caffeine