Both ESI and MALDI can be used with ion trap analyzers. Ion trap consists of a chamber surrounded by a ring electrode and two end-cap electrodes. It can trap ions in a radio frequency quadrupole field.
Ions above a certain m/z threshold remain in the trap. Ions are ejected based on applied voltage. So a mass spectrum can be obtained by gradually increasing the voltage. Alternatively, an inert gas can be inserted to fragment the ions. Multiple rounds of fragmentation can be used.
Ions trap is capable of isolating ion species by ejecting all other from the trap. This is usually done to repeatedly fragment ions of interest. This significantly increases the amount of structural information which can be gathered.
Ion traps separate ions in time.
Ion trap is ideal for glycosylation analysis since it can break down sugars sequentially.