A method is disclosed for controlling the direction and transport of a material on a microfluidic device formed from an acrylic polymer, by electrokinetic flow of a fluid containing the material. The method comprises providing an electrokinesis buffer containing a charged hydrophilic polymer, wherein charges on the polymer are randomly distributed. The method has applications for improved transport of proteins and transport of materials comprising differentially charged chemical species. A preferred embodiment of the present invention comprises use of the disclosed method for electrokinetic separations of a mixture of polypeptides having both positive and negative charges. Another preferred embodiment concerns use of the disclosed method for performing an assay involving mixing of two or more reagents, wherein a first reagent comprises an enzyme and a second reagent comprises species having an opposite charge to the enzyme.