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.