Relative efficiency of molecular sieving in solutions of four polymers

The efficiency of size separations of polystyrene sulfate, 120-1085 nm radius, by molecular sieving in polymer solutions, expressed by the separation efficiency function S = M0 magnitude of dKR(R)/dR Te-KR(R)T [where M0 is the mobility in free solution, KR the retardation coefficient, R the geometric mean radius of the particle, KR(R) the retardation coefficient as a function of R, and the polymer concentration is T] increases from methylhydroxypropyl cellulose to polyvinyl alcohol to uncrosslinked polyacrylamide to agarose above its gelling temperature. Separations of DNA, in the size range of 3-21 nm radius, are by at least one order of magnitude more efficient than those of polystyrene sulfate in the size range of 120-1085 nm radius. A plot of S vs. R in the experimental range of T is constructed for the four polymer solutions; this allows one to select optimal media and concentrations for the sieving of particles in the desired range of molecular sizes.