Application of microdialysis for on-line coupling of capillary isoelectric focusing with electrospray mass spectrometry on a magnetic sector instrument

The on-line coupling of capillary isoelectric focusing (CIEF) with electrospray mass spectrometry (MS) by means of microdialysis (MD) for application to three carbonic anhydrase isozymes is described. The dialysis device consisted of a donor and an acceptor compartment that were separated by a flat membrane, and served to clear the CIEF effluent that was directed to the mass spectrometer from ampholytes that were necessary for the establishment of a pH gradient in the IEF capillary. In addition to single-ion monitoring and full-scan experiments, a position-and time-resolved ion counting (PATRIC) detector was used in the static array mode. For CIEF/MD/MS of unknown proteins the minimum amount of analyte required for the analysis was estimated to be in the mid-femtomole range using full-scan MS data acquisition. (C) 1998 John Wiley & Sons, Ltd.