Electrospray ionization using magnetic sector mass spectrometers

Electrospray Ionization (ESI) has become a routine technique of enormous importance for analysis of biomolecules like proteins and peptides. Application of ESI to biological problems can benefit from the mass resolution and mass range of double focusing magnetic-sector mass spectrometers because of their high resolving power and sensitivity. One particularity of ES sectors is the complexity of the interface design due to high potentials of sector instruments. Detection limits are related to the mass spectrometer transmission and the detector sensitivity. In the case of sector instruments with array detection, the problem of dispersion can partially be removed. For example, hen egg-white lysozyme was detected at concentrations down to 500 attomol/mu l and a high quality spectrum was obtained for only 10 femtomol of sample consumed. Nevertheless, high resolution work on magnetic sector instruments requires very intense and stable ion currents, often not easily achievable when sample amounts are limited. Several improvements have been suggested, on one hand by increasing the efficiency of ion transmission from the source to the analyzer region, on the other by miniaturizing the spray process. In conclusion, magnetic sector instruments seem to have great potential for ESI-MS.