The invention concerns a method for separating at least a constituent of a mixture in a set of looping chromatographic columns, the loop comprising at least a point for injecting a load, a point for drawing off the raffinate, a point for injecting an eluting agent and a point for drawing of the extract. The method consists in: determining between an injection point and a drawing off point or vice-versa a chromatographic zone and at the end of a specific time interval, the whole set of injection points and drawing off points are offset by the same number of columns or column sections and advantageously from one column or one column section in a specific direction defined with respect to that of the flow of the main fluid circulating through the loop. During said time interval, the offsetting of the different injection and drawing off points of at least one column or column section is carried out at different times such that the length of the zones defined by the different points varies. The invention is useful in particular for separating stereoisomers for pharmaceutical purposes.