Recent Advances in Capillary Electrochromatography of Proteins and Carbohydrates in the Biopharmaceutical and Biomedical Field

Capillary electrochromatography (CEC) is a powerful hybrid separation technique that combines capillary electrophoresis and capillary chromatography, capable to address the analytical challenges of proteomics and glycomics. The focus of this paper is to review the recent developments in capillary electrochromatography of proteins and carbohydrates. The different column types applied in capillary electrochromatography such as packed bed, open tubular and monoliths are conferred in detail with respective separation examples. A comprehensive comparison is also given listing the mostly utilized coating methods, stationary phase materials and column preparation methods. The choice of porogenic solvent combinations for monolithic column fabrication is thoroughly discussed, paying close attention to the fine tuning options for the separation driving electroosmotic flow. Application examples of CEC in process analytical technology for the biopharmaceutical and biomarker discovery in the biomedical fields are also given.

Capillary electrochromatography with polymeric continuous beds synthesized via free radical polymerization in aqueous media using derivatized cyclodextrins as solubilizing agents

A novel synthetic route to amphiphilic acrylamide-based monolithic stationary phases for capillary electrochromatography (CEC) employing water-soluble cyclodextrins as solubilizing agents was explored. N,N'-Octamethylenebisacryamide and N,N'-dodecamethylenebisacryamide were synthesized and their solubilization in aqueous solution with derivatized and underivatized cyclodextrins of different cavity size was studied. Amphiphilic stationary phases were synthesized by free radical copolymerization of the bisacrylamide-cyclodextrin host-guest complexes with hydrophilic monomers and an additional hydrophilic cross-linker in aqueous solution. Complex formation in solution and removal of the complexed cyclodextrin from the polymer during synthesis was studied with 1H-NMR and solid state 13C-NMR spectroscopy and cyclodextrin-modified micellar electrokinetic chromatography. The impact of the incorporated alkylene groups in the acrylamide-based macroporous polymer on retention was studied with neutral solutes by CEC in the normal-phase elution mode and in the reversed-phase elution mode. Batch-to-batch reproducibility of the synthesis procedure and day-to-day repeatability of the separations achieved were investigated. With these capillaries, a sufficiently high electroosmotic flow velocity, a high reproducibility and repeatability of separation parameters and high plate numbers (up to 200,000 m(-1) were obtained.

Parametric investigation on the effect of channel topologies on electrophoretic separations

This paper presents a systematic study that illustrates the importance of the topologies of microchannels on electrokinetically based separation. Using theoretical and numerical analyses, we designed and showed that topologies that significantly increased the surface-to-volume ratio of the channel can provide dramatic improvement in the ability of the channel both to dissipate the heat generated by Joule heating and to reduce the axial dispersion associated with the siphoning effect. The incremental benefit and tradeoff of geometric complexity was also evaluated. The improvement offered by topographically patterned channels, such as finned structures, is especially pertinent in the development of preparative or semi-preparative scale electrokinetically driven separations, such as capillary electrophoresis and capillary electrochromatography, in which large cross sections of channels are required to achieve the needed volumetric throughput.