Matrix‐assisted laser desorption/ionization inside a quadrupole ion‐trap detector cell

An ion‐trap detector has been modified for matrix‐assisted laser desorption/ionization using a pulsed frequency‐quadrupled Nd: YAG laser and extended mass range up to 3300 u using the resonant‐rejection mode of operation. The matric‐assisted laser desorption/ionization mass spectra of a number of peptides are reported, and the effects due to the synchronization of the laser pulses and the phase of the RF voltage applied to the ring electrode are described.