Abstract: The invention recognizes the deleterious effects of trace, and even undetectable amounts of multivalent cations on the separation of mixtures of polynucleotides, especially double stranded polynucleotides, and provides an improved method for separating such mixtures on wide pore, non-polar separation media by eliminating multivalent cations from the all aspects of the separation process. This is accomplished by using components in the separation process which are materials which do not release metal cations. In addition, the use of cation capture resins and other methods to remove residual traces of multivalent cations from eluting solvents, sample solutions, separation media, and system components is described. It is also important to remove any traces or organic contaminants from solvents solutions and system parts.