FAB or LSIMS analysis is normally used for samples that are insufficiently volatile to be analysed by electron impact or chemical ionisation. Samples run by LSIMS tend to be of medium to high mass range, our Zabspec has a mass range of 10,000 Daltons at 8Kv accelerating voltage.
In LSIMS the sample is placed on a small stainless steel target, dissolved in a liquid matrix e.g. 3 nitrobenzyl alcohol or glycerol. The target is then inserted into the instrument and the sample is bombarded with an energetic primary ion beam of caesium ions. Molecules are sputtered from the surface of the liquid which then enter the gas phase and are ionised to beams of secondary ions.
In FAB the technique used is similar but ions are produced by bombarding the liquid surface with an energetic beam of inert gas atoms such as Xenon or Argon.