An arrangement forthe removal of one or more fractions out of whole blood, plasma or other similar body fluids with the help of adsorption on an adsorption column (23,24) comprising means for the feed of the said fluid of the column and means for the removal of the same. In accordance with the invention the said means for the removal of the fluid comprise at least one analysing device (31,32) for the coarse analysis of the fluid and a valve device (33,34) which is adapted so as to conduct the fluid flow from the column (23,24) as a function of the analysis carried out either to a second analysing device (38,46,47) for the fine analysis of the fluid or back to the source (1) of the same, e.g. a patient, or to a drain (36). The arrangement can be eluated with the help of a regenerating liquid which is adapted so as to tower the pH of the column gradually during a certain period. Preferably means are adapted so that at the start of the period a rapid loweing is achieved so as to accelerate the starting of the regeneration, whereupon the lowering is adapted so as to occur slowly during the actual regeneration, and appropriately to be terminated rapidly during the finish of the said period.