ETD Source Operation
The ESI source incorporates a fast and efficient intermediate pressure glow discharge reagent anion source. During the ETD experiment, cations and anions are sequentially generated. The ion source polarity and quadrupole set mass are switched to deliver multiply charged precursor cations followed by singly-charged reagent radical anions (usually from 1,4-dicyanobenzene [m/z 128]) into the Trap T-Wave ion guide, where they interact to form ETD product ions.
Reagent anions formed in a glow-discharge source are trapped in the instrument’s Triwave Trap T-Wave ion guide, where they undergo rapid electron-transfer reaction with analyte ions. Multiply charged peptide ions fragment by ETD to give predominantly c-fragment and z-fragment ions.
The formation and trapping of the reagent anions, and formation and reaction of sample ions are separate processes. When operating in ETD mode, the instrument alternates between a glow-discharge mode that effectively refills the Trap T-Wave ion guide with anions and an ESI mode that ionizes the sample and reacts it with the ETD reagent anions.
During acquisition, the Trap T-Wave ionguide is used exclusively for ETD, but the Transfer T-Wave ion guide remains available for CID. It is therefore possible to acquire both ETD and CID data in the same experiment.
