Theoretical considerations of molecular sieve effects

Abstract The separation of molecules in neutral gel and controlled-pore glass columns is studied on the basis of a statistical model. The theoretical results are compared with experimental results obtained from Sephadex gel columns. The good agreement between theoretical and experimental results over the whole working range enables complete calibration of columns with just one reference molecule and a knowledge of the void volume, V o . By means of the derived equation, the molecular weight can be calculated from the elution volume with greater accuracy. The equation also permits the calculation of the elution volume of aggregates of molecules which can assume different sterical conformations with high frictional ratios. An accurate functional correlation between elution volume and molecular weight applicable over the whole working range not only makes analytical steric chromatography less time-consuming but also renders it more amenable to automation. Providing active transport can be neglected, the derived equation may also be valid for filtration across membranes and synapses.