Properties of entangled polymer solutions in high-performance capillary electrophoresis

The influence of the nature and chain length of polymers in a sieving polymer solution on the effective electrophoretic mobilities of proteins in gel electrophoresis is described. Two types of polymers are used in this study, a linear polymer, polyethyleneglycol, and a branched polymer, dextran. Properties and performance of polymer solutions are compared at various temperatures and methanol concentrations. The overlap threshold, which is the concentration of the polymer at which the polymer chains start to entangle, is used for this comparison. The various overlap thresholds of polymer solutions are determined both with Ubelohde viscosimetry and capillary electrophoresis. An experimental design is used to minimize the required number of experiments. Multivariate analysis is applied to elucidate the magnitude of the effects quantitively. It is demonstrated that changes in electrophoretic mobility of the test compounds are not caused by changes in the gel structure but can be fully explained by the variation of viscosity with temperature. It is also shown that addition of methanol to polymer solutions not only contributes to differences in viscosity but probably also influences the structure of the sieving polymer networks. Furthermore, it is shown that the chain length of the sieving polymer significantly influences the structure of the polymer network in the polymer solution