Mass analyzers space charge effects

An alternative approach was introduced by Hunt and co-workers [87], Those researchers coupled a linear quadrupole ion trap, consisting of four rods of hyberbolic cross-section, with an FT-ICR mass spectrometer. The linear ion trap allows accumulation of larger populations of ions than does a standard three-dimensional (3D) ion trap. The hybrid linear ion trap-FT-ICR instrument enables simultaneous detection in both mass analyzers. This aspect is particularly advantageous for data-dependent MS/ MS methods used in proteomics, and is discussed further below. The commercial version of this instrument features automated gain control that accumulates a fixed number of charges before delivery to the ICR cell. Because the ideal ion density is attained in the cell, space-charge effects resulting in loss of mass resolution and mass accuracy, are eliminated. 

Both 3D and linear ion-trap analyzers are widely used in lipidomics [67-72]. Generally, these analyzers have good sensitivity, possess high-throughput capability, and allow multistage tandem MS analyses. However, these ion-trap analyzers suffer from poor mass resolution, low dynamic range, and space-charge effects that do not allow very accurate mass determination or quantitation. 

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