A new method of trapping ions produced by matrix‐assisted laser desorption lonization in a quadrupole ion trap

A novel method for trapping ions produced by matrix‐assisted laser desorption ionization (MALDI) using controlled gating of the trapping field is suggested. Because it does not use collisions with helium atoms for reducing ion kinetic energy, trapping can be accomplished at low pressures of the buffet gas. The method has been implemented on an ion‐trap detector, modified for MALDI experiments inside an ion trap with axial introduction of the sample probe. High mass resolution (1 part in 12 000) is reported.