Almost atom bombing
Fast Atom Bombardment (FAB) is an ionization technique usedin mass spectrometers (MS). Here, a solution of the analyte in a liquid, poorly volatile matrix is bombarded with a particle stream of usually inert gases such as argon or xenon (3-8 keV). The usual matrices are glycerine or 3-nitrobenzyl chloride . This technique is closely related to secondary ion mass spectrometry . One speaks of Liquid Secondary Ion Mass Spectrometry (LSIMS) when fast ions (Cs + , up to 35 keV) are usedinstead of noble gas atoms.
Compared to electron impact ionization, FAB is a “gentle” ionization process and mainly produces protonated molecules such as [M + H] + or deprotonated molecules such as [M − H] - . The type of ionization products puts FAB in close proximity to processes such as chemical ionization (CI), electrospray ionization (ESI), chemical ionization at atmospheric pressure (APCI) ( Atmospheric Pressure Chemical Ionization ) and matrix-assisted laser desorption / ionization (MALDI) ( Matrix Assisted Laser Desorption / Ionization ).
FAB was used in routine analysis from around 1980. Due to the lower sensitivity, poorer ion yields and the high degree of contamination in the ion source , this ionization process has been replaced by ESI, APCI and MALDI since the beginning of 1990. The coupling of high-performance liquid chromatography with FAB-MS is also much more complex and less efficient than that with ESI or APCI-MS.