MALDI-TOF Mass spectrometry is a methode to measure the mass of molecules by measuring their time-of-flight in a evacuated tube with no electric and magnetic fields. The method requires a "start" signal (laser pulse) and a "stop" signal given by the signal created by a detector hit by the molecule at the end of the tube.
The following video illustrates this principle:
The following figure shows the relevant mathematical quantities in a MALDI-TOF mass spectrometer:
The method to launch and charge molecules in a vacuum is done by the method developed by Karas & Hillenkamp in 1984: MALDI = matrix assisted laser desorption and ionization. The molecules to be analyzed are diluted in a UV absorbing matrix solution which is then crystallized. When hit by the laser pulse of width of a few nanoseconds the matrix crystals are "evaporated", dragging the molecules with them. A sufficiently large number of molecules survive this process intact and can be accelerated and focussed onto the detector.
