REDUCED ELUTION SPEED DETECTION FOR CAPILLARY ELECTROPHORESIS MASS-SPECTROMETRY

A combined capillary electrophoresis/mass spectrometry (CE/MS) method is described that provides an increase in the efficiency of analysis by decreasing the analyte elution rate into an electrospray ionization (ESI) interface. The method is readily implemented by instituting a step change in the CE electric field strength for desired periods of time during a separation. As a result, the m/z range or the number of times an m/z range can be scanned while a solute elutes is increased by a factor proportional to the decrease in CE electric field strength. In addition, the method is shown not to cause any significant loss in separation quality as demonstrated for mixtures of proteins and peptides, while providing an effective gain in sensitivity. This allows an enhancement in the quality of mass spectra recorded while scanning wide m/z ranges. Mass spectra for a set of standard proteins were obtained for injections of 60 femtomole/protein, while analysis of an albumin tryptic digest was obtained for injections corresponding to 40 femtomoles of protein.