A new device for ultrafiltration. The ultrafiltrability of calcium and inorganic phosphate in human serum.

The various problems concerning the ultrafiltration of blood serum are outlined, and a novel ultrafiltration device, which overcomes all these problems is presented. Its main advantages are the following: (1) The deposition of protein on the filter is prevented by producing a flow across the filter surface. (2) The pCO2 remains constant, since the fluid is not in contact with a gas space. (3) The minimum serum volume is only 0.4 ml (4) Six samples can be processed simultaneously. (5) All commercially available filter types can be used. The machine, tested by measuring the ultrafiltrability of calcium, inorganic phosphate, sodium and chloride in human serum, proved to be a reliable laboratory tool. The precision of the determinations were comparable to respective serum analyses. The ultrafiltrabilities obtained, without correction for water content of serum, were 55.6 +/- 2.9% for calcium, 88.3 +/- 5.0% for inorganic phosphate, 95 +/- 1.7% for sodium, and 103 +/- 0.7% for chloride (means +/- S.D.).