Protein analysis by isoelectric focusing in a capillary array with an absorption imaging detector.

Isoelectric focusing (IEF) was successfully performed in capillary arrays with up to four capillaries. Separated proteins in the capillary array were detected by an UV absorption imaging detector. The whole analysis time for all samples in the capillary array was only 3 min due to the real-time imaging detector. The instrument was applied to analyse several protein samples including different human hemoglobin variants, myoglobin, transferrin, carbonic anhydrase and a monoclonal antibody to fluorescein. Because of good reproducibility of the focused pattern, unknown samples can be run simultaneously with a standard in the multichannel instrument and the components of unknown samples can be identified by comparing their zone positions to those of the standard. Minor components can be determined by the instrument in the presence of major components with 100 times higher concentrations in human hemoglobin samples. This instrument could be a powerful analytical tool for clinical analysis and for quality control in pharmaceutical companies.