Analysis and Prediction of Sieving Curves for Ultrafiltration Membranes: A Universal Correlation?

Abstract Sieving curves [variations in sieving coefficient (θ) with Einstein-Stokes radius (α) of the permeating macromolecule] of a number of synthetic ultrafiltration membranes, and of a variety of mammalian glomerular membranes studied in vivo, conform surprisingly closely to a log-normal-probability relationship between θ and α which allows determination of the complete sieving curve from experimental measurement of only two sieving coefficients for two macrosolutes of differing ESR. Even more striking is the finding that, for all membranes examined, the value of α corresponding to θ = 0.5 (the inflection point in the sieving curve) varies only between 17 and 34 Å, and geometric standard deviation about the mean macrosolute radius ([sgrave]α), which is inversely related to the “sharpness” of the sieving curve, lies between 1.2 and 1.7. It is concluded that not only is the log-probability correlation a reasonable and convenient means for interpreting and predicting membrane sieving data, but that most natural and synthetic ultrafiltration membranes have very closely related matrix morphologies.