High-performance capillary electrophoresis of human serum and plasma proteins

In recent years, capillary electrophoresis has proved extremely useful for separation of biomolecules such as nucleotides, amino acids, peptides, and proteins. The advanced instrumental design of commercial CE equipment has offered several advantages to conventional electrophoresis. Precise sample application, temperature regulation, and stable, reproducible instrument control with respect to voltage, current, pressure, and run-to-run reproducibility is routinely achieved in contemporary commercially available equipment. Based on these instrumental features, CE is already used as a routine method for the analysis of small molecules. In contrast, serum and plasma proteins represent a difficult challenge for capillary electrophoresis. Routine analysis of serum and plasma proteins is reduced to the application of capillary zone electrophoresis, which proved to be a reliable method for rapid screening of whole serum, purity control of serum proteins and fractions, as well as on-line quantification of the components. With regard to the simplicity of the method and the low cost of operation, CZE proved to be an attractive alternative to comparable conventional methods. Other separation techniques, such as CITP, CIEF, and CGE, provide higher resolution of the sample proteins than that provided by CZE. Furthermore, information about physicochemical properties of the analyte, such as isoelectric point or molecular weight, can be gained by CIEF or CGE. Even though this information is essential for protein analysis and characterization, these methods are not commonly used at present because reliable methods for controlling the EOF are not commercially available. Coated capillaries are expensive, and it is still difficult to purchase a set of coated capillaries with identical properties. As long as the reproducibility from capillary to capillary cannot be guaranteed, the high resolving methods will not be applied in routine analysis. The development of reliable regulation of the EOF, either by an appropriate column material or coating or an external field control, will certainly lead to a breakthrough for the capillary electrophoresis of human serum and plasma proteins.