Capillary zone electrophoresis–mass spectrometry with electrospray ionization of peptides and proteins

Abstract

Capillary zone electrophoresis (CZE) coupled with an on‐line mass spectrometric (MS) detection system by an atmospheric pressure electrospray ionization (ESI) interface has been used successfully for Separations of peptide and protein mixtures. For CZE‐MS, ESI produces multiply charged molecular ions and thus allows mas spectrometers with a limited mass‐to‐charge range to analyze proteins having molecular weights greater than 100,000. Various pH buffer systems have been investigated, including buffer systems in which pH > pI (isoelectric point of analytes) and pH « pI are designed to reduce protein adsorption onto silica capillary surfaces and thus improve separation efficiencies. More than 125,000 theoretical plates have been obtained from a CZE‐MS separation of less than 1 pmol per component of leucine enkephalin and horse heart myoglobin. CZE‐MS of other large peptides and proteins are demonstrated.