Affinity Countercurrent Chromatography Using a Ligand in the Stationary Phase

In countercurrent chromatography (CCC), an addition of a ligand to the liquid stationary phase remarkably improved both retention time and peak resolution of the analytes: various amino acid derivatives were separated by N-dodecanoyl-L-proline-3,5-dimethylanilide, while polar catecholamines and dipeptides were separated by bis-(2-ethylhexyl)phosphoric acid. By selecting an appropriate ligand and dissolving it in the liquid stationary phase, the present CCC technique can perform a variety of separations comparable to chiral chromatography, ion chromatography, and affinity chromatography. Leakage of the ligand from the column can be entirely eliminated by introducing a small volume of a ligand-free stationary phase at the end of the column as an absorbent. The method further facilitates application of pH-zone-refining CCC and can increase the sample loading capacity over 10 times for a given column.