ABSTRACT
The fundamentals of the ion optics for magnetic and electric sector, quadrupole, ion trap, and Fourier-transform ion cyclotron resonance (FTICR) mass spectrometers range from fairly simple to difficult. The basic ion optics of time-of-flight (TOF) instruments are very straightforward. Basically, ions need to be extracted from an ion source in short pulses and then directed down an evacuated straight tube to a detector. The time taken to travel the length of the drift or flight tube depends on the mass of the ion and its charge. For singly charged ions (z = 1; m/z = m), the time taken to traverse the distance from the source to the detector is proportional to a function of mass: The greater the mass of the ion, the slower it is in arriving at the detector. Thus, there are no electric or magnetic fields to constrain the ions into curved or complicated trajectories. After initial acceleration, the ions pass in a straight line, at constant speed, to the detector. The arrival of the ions at the detector is recorded in the usual way: as a trace of ion abundance against time of arrival, the latter being converted into a mass scale to give the final mass spectrum.
