Capillary isoelectric focusing with whole column detection and a membrane sample preparation system Review Article

Progress of the research on capillary isoelectric focusing (cIEF)–whole column detection is reviewed. Three kinds of whole column detectors have been developed for cIEF: universal refractive index gradient imaging detector, laser-induced fluorescence (LIF) imaging detector, and optical absorption detector. Principle, applicability and detection limit of these detectors are discussed. A capillary column cartridge specially designed for cIEF with whole column detection is introduced. The column cartridge uses microdialysis hollow fiber membranes to isolate the sample solution from the electrolytes. Sample can be directly injected into the column without disturbing the electrolytes using a syringe pump or a liquid chromatography autosampler. The cartridge incorporates an on-line desalting, carrier ampholytes mixing device which also uses a microdialysis hollow fiber membrane. The on-line device adapts cIEF to a variety of analytical matrices. Examples of application of different whole column detectors to cIEF are shown in the review.