Negative plate mixed potential

Fig. 5.3. Schematic of the mixed potential, established at the negative plate of a lead add...

Fig. 9.2. Model depicting mixed-potential condition at negative-plate surface due to simultaneous functioning of hydrogen-evolution zones and oxygen-recombination gas paths.

Thus, ETD lends the capabilities of ECD to linear ion trap mass spectrometers. The individual steps involved in the operation of an LTQ instrument in ETD mode (Fig. 9.39) are injection of multiply protonated peptides as delivered by an ESI source application of a DC offset to store these ions in the front section of the LIT followed by injection of reagent anions from the Cl source into the center of the LIT. Then all but the peptide precursor ions and the electron-donor reagent ions are ejecteeL Next the DC potential well is switched off and a secondary RF voltage is applied to the end lens plates of the LIT causing positive and negative ion populations to mix and react. The reaction period is ended by axial ejection of reagent anions while positive product ions are retained in the center section of the LIT. Finally, mass-selective radial ejection as usual yields the ETD spectrum [160]. The attractive ETD technique has also been implemented on LITs with axial ejection [144,166] and on LIT-orbitrap hybrids [167-169]. 

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