The importance of formaldehyde purity in studies on the electrokinetic charge of human red cells.

Electrokinetic measurements and rheological studies conducted in parallel have previously shown red cell surface charge to play a role in governing aggregative behavior and bulk flow properties of red cell suspensions. For these and other types of model investigations, aldehyde stabilized cells have been widely used. In this communication, the influence of the purity of formaldehyde was investigated. It was found that (a) the direct dissolution of commercially available paraformaldehyde in water or suitably buffered saline results in impure solutions which, if utilized in the fixation of human erythrocytes, produces cells which have significantly different electrophoretic properties from native cells; (b) the basis for the differences is the presence of metallic impurities in some commercially available paraformaldehyde preparations; (c) the impurities and thus the anomalous electrokinetic properties of the fixed cells may be eliminated by generating formaldehyde gas from paraformaldehyde by heating the latter to 203-210 degrees C; (d) alternatively, the impurities may be eliminated by addition of disodium ethylenediamine tetraacetate dihydrate to fixative solutions prepared directly from paraformaldehyde.