Linear RF-Only Multipole Ion Traps

Note Quadrupoles are the only devices capable of mass-selective operation, whereas higher-order RF ion guides or higher-order LITs can only guide, accumulate, store, and finally release ions for subsequent m/z analysis. 

While the entrance plate of the LIT is held at low potential, ions may enter the radially ion-confining RF field. The time span for ion accumulation is limited by reflection of the fast ions at the backside potential wall affording that the entrance gate has to be closed before the lightest ions to be stored can exit the trap via the entrance (Fig. 4.34). Storage of ions in the presence of some buffer gas, e.g., argon or nitrogen at mbar, then allows for their thermalization and collisional 

LITs capable of scanning by either axial or radial excitation of the ions and even capable of precursor ion selection for MS/MS experiments [108,109,113] have lately been incorporated in commercial mass spectrometers [96,114-116]. 

Note Here, we have gone beyond the domain of the classical mass spectro-metric time scale (Chap. 2.6.2). In ion trapping devices, ions are stored for milliseconds to seconds, i.e., 10 -10 times longer than their lifetimes in beam in-stmments. 

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