The
Centre has a Kratos MALDI 3 for MALDI-TOF analysis of
polymers and proteins. The machine can analyse hydrophilic
and hydrophobic polymers to around 5000 amu; this is increased
up to a molecular mass of around 15,000 amu for proteins.
The machine can be used in linear or reflectron mode and
analyse positive or negative charge carrying species.
MALDI-TOF stands for Matrix Assisted Laser Desorption
Ionisation- Time Of Flight. It is a soft ionisation technique,
which means that the analyte is not fragmented during
the operation. The laser light is absorbed by the matrix
which sends a cloud of charged particles down the evacuated
flight chamber. The flight time is proportional to the
mass and charge of each particle. The spectra consists
of a series of peaks which contain information about mass/charge
ratio and intensity of particular charged species.
Unfortunately
MALDI shows a non linear mass dependent response, this
excludes MALDI from being used for complete molecular
weight distribution analysis. MALDI is particularly
useful for the analysis of very narrow polydispersity
polymers, endgroup and chain composition.
