Resolution of cells by centrifugal elutriation

Cell separation using the Beckman elutriator depends upon the flow rate of the medium and the centrifugal field employed. Changes in either the centrifugal field or the flow rate can be used to elute fractions of cells based on size. Even when these variables are held constant in the Beckman J21C centrifuge, a periodic pulse of cells is eluted. We have found that this anomolous elution is related to the temperature control system which gave a periodically pulsed temperature drop in the centrifuge well. The elution resulting from this change in temperature caused a shift in the modal cell size of the fraction eluted at a particular flow rate and centrifugal field. Because of this, the fractions have a larger size dispersion than fractions collected under conditions where refrigeration-related temperature fluctuations do not occur. We conclude that the temperature control system of the Beckman J21C centrifuge used with the Beckman elutriation rotor produces temperature fluctuations which prevent maximum resolution of cells.