Laser Desorption Time-of-Flight Mass Spectrometry of High Mass Molecules

A laser desorption time-of-flight mass spectrometer Is described which uses a high-power, moderately focused, pulsed beam from a CO2 laser. Unlike the laser microprobe instruments, extended desorption follows the laser pulse, so that acceleration Is accomplished with a drawout pulse. The major Ionization process, cationization, Is consistent with a thermal model. Delaying the drawout pulse has some distinct advantages, particularly as molecules of higher molecular weight are studied. Delayed drawout pulsing samples Ions of lower energy spread and of varying degrees of fragmentation and can also be used to control metastable decompositions which occur In the accelerating region of the mass spectrometer. A number of peptides, glycosides, and other nonvolatile compounds provide examples of the analytical technique.