Some Effects of Nonreacting Substances in the Quantitative Application of Gel Diffusion Techniques

Summary In Oudin’s gel diffusion technique, the rate of advance, k, of the zone of precipitation may be used to determine the concentration of antigen or antibodies. Substantial errors can result, however, from the fact that nonreacting contaminants of the antigen or antibody layer can also affect k. Nonreacting contaminants were observed to affect k by three mechanisms: their influence on convection currents in the antigen layer, their contribution to the viscosity of the antiserum layer, and a third mechanism which is effective when the distribution of the contaminant between the two layers is grossly unequal (e.g., greater than 0.2 M sucrose). The reliability of gel diffusion techniques for quantitative work is greatly improved if these effects are controlled by the methods recommended.