Chromatographic behaviour of aromatic compounds on gel filtration Media

Summary

Highly cross-linked gels utilized as gel filtration media exhibit adsorption effects towards aromatic or apolar compounds. The adsorption is linearly dependent on salt concentration.

We investigated the effect of various salts spanning the Hofmeister series on the adsorption of three model compounds, Adenosine 5′-phosphate, ε-dinitrophenyllysine and tryptophan.

It was found that salts exhibiting marked salting-out properties, such as potassium phosphate and sodium sulfate, were the most effective in enhancing the adsorption were the most effective in enhancing the adsorption of the aromatic molecules onto the gel. On the contrary, in the presence of salts with marked salting-in properties, such as Kl or KSCN, the linear dependence of elution parameters for the same compounds was negatively correlated and adsorption decreased with salt concentration. However, a number of salts of intermediate character in the Hofmeister series, such as NaCl or NH₄Cl, did not affect the elution behaviour of the chosen model compounds.

The different effects observed are probably due to differential hydration of the molecules in the presence of the salts and to the consequent different hydrodynamic behaviour of the solute when interacting with the hydration layers of the gel matrix.