An ultraviolet/infrared matrix-assisted laser desorption ionization sample stage integrating scanning knife-edge and slit devices for laser beam analysis

A sample stage is described that allows the on-line analysis of laser intensity profiles and spot sizes directly in the ion source of a matrix-assisted laser desorption ionization (MALDI) mass spectrometer. The detector uses either a scanning knife-edge or a narrow slit in combination with diffusing disks for scattering of photons and a pyroelectric sensor for recording the light pulses. The setup was integrated into the sample holder of a oMALDI2(TM) ion source (AB Sciex) and allows parallel analysis of UV- and IR-laser beams at typical UV-/IR-MALDI laser fluences. The concept could be especially useful for a precise control of the laser spot size in MALDI imaging applications.