Tandem mass spectrometry with time-of-flight analyser

4 Tandem Mass Spectrometry with Time-of-Flight Analyser 

If mv is the mass of the precursor and m( the fragment mass, their respective kinetic energies kp and kr are, since they have the same velocity uLl, 

The penetration depth d in the reflectron is given by d = EJqE. Hence, for the precursor and the fragment, the relevant equations are 

TOF spectrometer fitted with a deflection electrode for precursor ion selection. The instrument can be operated in either the linear or the reflectron mode. The selection resolution is about 250, which for example gives a 4Th window at m/z 1000. 

The necessity to step the voltage applied to the reflectron to produce a complete spectrum consumes time, wastes sample and complicates the mass calibration procedure. Indeed, the acquisition of a PSD spectrum is at least 20 times longer than for a classic TOF spectrum and the main part of the sample is lost without contributing to the analysis. 

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