[Quantitative protein estimation following standardized concentration of diluted physiological fluids (author's transl)].

After the tenfold concentration of 1:100 diluted standard solutions in the Minicon B-15 concentrator, the quantitative determination of total protein and of ten single proteins showed a decreased yield. These losses are not standardizable. The reason is analyzed and discussed. Therefore, the quantitative estimation of single proteins by means of immunochemical methods as well as the densitometry of electrophoreses of dilute protein solutions following concentration should be interpreted with caution, because changes in the absolute and relative concentration of proteins are to be expected. These methods are not suitable for exact measurements. An unstandardizable correction coefficient ought to be considered.