not shown in the figures or described herein to maximise ion transmission between various parts or stages of the apparatus various vacuum pumps not shown may be provided for maintaining optimal vacuum conditions in the device the time of flight mass analyser 5 incorporating a reflectron operates in a known way by measuring the transit time of the ions comprised in a packet of ions so that their mass to charge ratios can be determined a control means not shown provides control signals for the various power supplies not shown which respectively provide the necessary operating potentials for the ion source 1 ion guide 2 quadrupole mass filter 3 collision cell 4 and the time of flight mass analyser 5 these control signals determine the operating parameters of the instrument for example the mass to charge ratios transmitted through the mass filter 3 and the operation of the analyser 5 the control means is typically controlled by signals from a computer not shown which may also be used to process the mass spectral data acquired the computer can also display and store mass spectra produced from the analyser 5 and receive and process commands from an operator the control means may be automatically set to perform various methods and make various determinations without operator intervention or may.