Answer 10.2

a) Enumerate the tasks of a liquid matrix as employed in FAB and LSIMS.

  1. It has to absorb the primary energy.
  2. By solvation it helps to overcome intermolecular forces between analyte molecules or ions.
  3. It provides a continuously refreshing and long-lasting supply of analyte.
  4. It assists analyte ion formation, e.g., by yielding proton donating/accepting or electron donating/accepting species upon bombardment.

b) Do you know at least three liquid matrices that are commonly in use?

Common liquid matrices for FAB and LSIMS

c) What properties should a good matrix have?

  1. The analyte must be soluble in the matrix.
  2. Only low-vapor pressure solvents can be easily used as a matrix in conventional FAB-MS.
  3. The viscosity of the solvent must be low enough to ensure the diffusion of the solutes to the surface.
  4. Ions from the matrix itself should be as unobtrusive as possible in the resulting FAB spectrum.
  5. The matrix itself has to be chemically inert. However, specific ion formation reactions promoting the secondary ion yield are beneficial.