Effect of membrane potential on dialysis of calcium in a continuous flow system

Abstract

It has been found that the estimation of calcium by continuous flow analysis using a 12 inch dialyser leads to discrepant results if acidified aqueous calcium standards are used as the means of primary calibration. We have examined the effects of hydrogen ion concentration on the dialysis of 45 Ca and compared the rates of dialysis with dialyser membrane potentials. The amount of calcium dialysed increased from 5% to 12% when the concentration of acid was increased on the recipient stream of the dialyser. This corresponded to a change in potential of 0 mV to + 24 mV of the donor stream with respect to the recipient stream. Further experiments including protein on either side of the dialyser show that the Donnan effect does not explain the differences in rate of dialysis between protein and aqueous samples and that the migration of H + does explain most of these differences.