Use of microdialysis for the on-line coupling of capillary isoelectric focusing with electrospray mass spectrometry

The coupling of capillary isoelectric focusing (IEF) with electrospray mass spectrometry (MS) has been described for the model proteins horse heart myoglobin, carbonic anhydrase I and beta-lactoglobulin A. An experimental set-up incorporating an IEF capillary and a transfer capillary which are connected by a dialysis fiber, enabling the implementation of microdialysis (MD), has been developed. Low-molecular-mass ampholytes that create the pH gradient in the capillary can be dialysed out of the system, while the proteins remain in the capillary, so that subsequent electrospray MS detection can be performed. To facilitate capillary IEF-MD-MS, acetic acid that can function both as anolyte and catholyte has been used. (C) 1997 Elsevier Science B.V.