Polymer- and surfactant-coated capillaries for isoelectric focusing

This paper reports a method for deactivation of fused-silica capillaries to be used in capillary isoelectric focusing (cIEF). Deactivation was achieved by adsorbing either a surfactant or hydrophilic polymer to alkylsilane-derivatized capillaries. The surfactant PF-108 and methyl cellulose reduced electro-osmotic flow (EOF) 20 to 30 fold in comparison to underivatized capillaries. Although EOF was reduced sufficiently to allow focusing to permit separations to be completed before proteins were swept through the capillary, there was adequate flow to obviate the need for a separate mobilization step. This reduces the complexity of cIEF and increases reproducibility. Based on resolution of hemoglobin variants, proteins that varied 0.03 pH units in isoelectric point were resolvable. This is equivalent to the highest resolution achieved in conventional slab and tube gel isoelectric focusing.