High-resolution mass spectrometry of large molecules in a linear time-of-flight mass spectrometer.

This report describes a new high-resolution linear time-of-flight mass spectrometer that has been constructed at this institute. The instrument is used for investigations of both direct and matrix-assisted laser desorption/ionization of large molecules. A unique feature of this new instrument is the incorporation of a 10-cm postsource pulse-focusing region for enhancing the resolution of the detected ion signals. This technique can correct for both high initial ion translational energies and long durations of ion formation and is expected to be particularly well suited for laser desorption/ionization applications. Results of calculations are presented to illustrate the gains in mass resolution that may be expected for a variety of ion formation conditions. In addition, initial experimental results are presented that demonstrate the capability of this new instrument to produce high-resolution ion signals. Signals with mass resolutions as high as 2750 (full width at half maximum) have been obtained for both direct and matrix-assisted laser desorption/ionization signals.