Mass spectrometry methods using electron capture by ions

Abstract

Methods and apparatus are provided to obtain efficient Electron capture dissociation (ECD) of positive ions, particularly useful in the mass spectrometric analysis of complex samples such as of complex mixtures and large biomolecules of peptides and proteins. Due to the low efficiency of ECD as previously used, the technique has so far only been employed with Penning cell ion cyclotron resonance mass spectrometers, where the ions are confined by a combination of magnetic and electrostatic fields. To substantially increase the efficiency of electron capture, the invention makes use of a high-intensity electron source producing a high-flux low-energy electron beam of a diameter comparable to that of the confinement volume of ions. Such a beam possesses trapping properties for positive ions. The ions confined by electron beam effectively capture electrons, which leads much shorter analysis time. The invention provides the possibility to employs ECD in other trapping and non-trapping instruments beside ICR mass spectrometers.