Capillary electrochromatography with packed bead beds in microfluidic devices

Microchip-based bead-packed columns for electrochromatography are described for several types of stationary phases. Chromatography columns 2 mm in length were used for the separation of proteins and peptides by size- and ion-exchange modes of separation, respectively. In size-exclusion electrochromatograpgy, FITC-IgG and FITC-insulin were baseline resolved in less than 10 s, with efficiencies of up to 139,000 plates/m for FITC-insulin. In strong cation-exchange electrochromatography, a mixture of three fluorescently labeled peptides was baseline resolved in less than 40 s, with efficiencies up to 400,000 plates/m. The RSD for the analytes retention times were<3% in both size-exclusion and ion-exchange modes of separations. The use of a 1-mm-long reverse-phase column for the semiquantitative evaluation of pharmaceutical formulations in drug solubility tests illustrates the use of this microfluidic chip-based electrochromatographic approach to drug development.