ETD on small intact proteins in an ultra high resolution quadrupole TOF mass spectrometer

The Bruker maXisTM is equipped with a nCI-source and a hexapolar ETD reaction cell. ETD Reagent anion and analyte ions were mass selectively transmitted through a mass resolving quadrupole. ETD reactions are performed in the reaction cell following the quadrupole, where the ions of different polarity are mutually stored. The ETD experiment (performed in trapping mode) consists of four steps: cation accumulation, anion accumulation, extension of the ETD reaction and finally the detection of the product ions in the orthogonal TOF. While ions are extracted, the next ETD experiment is performed in the reaction cell thus maximizing duty cycle.