Advanced online mass spectrometry detection of proteins separated by capillary isoelectric focusing after sequential injection.

Capillary isoelectric focusing hyphenated with mass spectrometry detection, following the sequential injection of the carrier ampholytes and the sample zone, is highly efficient for the characterization of proteins. The main advantage of the sequential injection protocol is that ampholytes, with pH ranges, which are not supposed to cover the isoelectric points of the sample components, can be used for separation. The method then allows online mass spectrometry detection of separated analytes either in the absence (substances that have left the pH gradient) or in the presence of low-level ampholytes (substances that are migrating within the pH gradient).