The TOF MS can be coupled as detector to a chromatographic system (e.g. GC, HPLC) or can be combined with a matrix-assisted laser desorption/ionization (MALDI) source or an atmospheric pressure ion source, e.g. the direct analysis in real time (DART™) ion source.
When coupling a TOF MS on a chromatographic system, different ionization sources are available. Beside the most widely-used electron impact ionization (EI) and chemical ionization (CI), various soft ionization techniques like the field desorption (FD), field ionization (FI), and liquid injection field desorption ionization (LIFDI) are used. The direct probe (exposure or insertation) allows the fast measurement of liquid or solid samples without previous chromatographic separation of the different components present.
MALDI is a soft ionization technique for mass spectrometry and used to analyse molecules which tend to be fragile when ionized by more conventional ionization methods (e.g. EI). Biomolecules, e.g. biopolymers such as DNA, proteins, peptides and sugars, and large organic molecules, such as polymers, dendrimers or other macromolecules, are just some examples of such molecules.
The DART™ ion source allows to probe samples without preparation by instantaneously ionizes gases, liquids and solids in open air under ambient conditions.