Supermolecular ion species in repetitive laser desorption mass spectrometry

Laser desorption time-of-flight mass spectrometry of high mass molecules

“…0003-2700/84/0356-1662$01.50/0 time following the laser pulse, during which the high temperature is dissipated by the substrate (8) and by the low, thermal energy spreads of the desorbed ions (10,11). The long-lasting desorption effects would seem less compatible with time-of-flight analysis which requires that the ions be formed and accelerated within a short time interval, and indeed the bulk analysis methods have been used largely, and quite successfully, with scanning instruments (1,12,13). There have been a number of different approaches to making such instruments compatible with the short ionization times from pulsed lasers.…”

“…This method could cover only a limited mass range, so that in the spectrum of digitonin only the molecular ion region was recorded. Heresch (12) has used repetitive laser desorption (RLD) to allow magnetic field scanning over a large mass range using several thousand laser pulses. However, such repeated exposure to laser radiation can result in sample damage during the course of the analysis.…”

Laser desorption mass spectrometry with thermospray sample deposition for determination of nonvolatile biomolecules

“…Ions are focused into the quadrupole entrance aperture by using two ion extraction cones and an einzel lens. The source lenses and quadrupoles are usually operated at a potential of [10][11][12][13][14][15] V with respect to the grounded belt. Differential pumping is supplied by a 1000 L/min mechanical pump on the thermospray region, a 2-in.…”

“…Cluster formation with metastable dissociation has been observed (12). With magnetic instruments large cluster ions formed in semifluid chemical ionization type reactions of sucrose have been observed (14). Cotter has determined the temporal distribution of laser desorbed neutrals and ions (15,16).…”