Development of Chip-based CE and CEC

Subsequent important contributions to the field of microchip CE were made early on by Jed Harrison and Andreas Manz, who reported a spectacular enhancement of device performance byredesigning the channel layout and increasing the applied electric fields [11], With an imposed field of 1 kV cm , six fluorescence-tagged amino acids were separated with baseline resolution in 15 s, generating 40 000 to 75 000 theoretical plates. In the improved design, the separation channel length was reduced from 13 to 2.2 cm, utilizing the same cross section as in the previous work. 

Michael Ramsey s group at Oakridge National Laboratories further improved device performance by introducing a 4-port crossed column geometry, giving independent control over sample and buffer flows [12]. This geometry has 

Capillary electrochromatography (CEC) is a method of chromatographically separating neutral analytes in an electroosmotically-generated flow. As with CE, the liquid matrix is propelled by an imposed electric field. Unlike capillary electrophoresis, however, solute molecules are not separated by differences in charge/mass ratio because they are neutral - thus a stationary phase is needed 

The COMOSS column was estimated to be equivalent to a conventional 4 pm non-porous bead packing. In addition, the surfaces of the structures were functionalized with a silane to form a C18 reversed-phase monolayer. To obtain the nanoliter per minute flow rates required to operate the devices, the authors relied on electroosmotically-driven flow using an electric field of 770 V cm thus operating in CEC mode, since mechanical HPLC pumps available at the time were not capable of delivering such a small flow at the pressures required. However, the column efficiency obtained was remarkable, with some 35 000 plates (777 000 plate m ) in 110 s obtained for unretained Rhodamine 123 on a column 

5 cm long, 10 pm deep and 150 pm wide [15]. These same workers also showed that the same C18-coated COMOSS device operating in isocratic CEC mode could resolve a peptide mixture derived from an ovalbumin digest in 10 min, almost as well as a conventional C18 packed HPLC column (4.6 mm X 2.5 m) using gradient elution could do in 50 min [17]. 

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