Aptamers can be employed for removing contaminants from a biological or chemical sample or isolating a desired component. The specific aptamers are immobilized on a chromatographic support. Due to their small size, a high degree of functonalization can be achieved. Aptamers are easy to graft on a support, are thermally stable, can be made resistant to nucleases and can even be used in some organic solvents. They are therefore of interest for the purification of a wide range of targets, including the separation of enantiomers.