Time-of-Flight Mass Spectrometry and High-Performance Electronics Control Technology

Time of flight mass separator is the major component of the quadrupole time of flight mass spectrometry (Q-TOF MS). Time of flight mass spectrometer (TOF MS) measures mass spectra by using the principle that different mass charge ratio ions have different flight times for same distance within a free flight field in vacuum. TOF MS has the advantages of microsecond-level fast detection speed, high ion transmission rate, high sensitivity and precision. Theoretically, there is no upper quality limitation which means large quality detection range. With its resolution increasing and these advantages, TOF MS is now widely used. The core factor affecting TOF MS resolution is that the initial kinetic energy and the initial position of ion are easily dispersed. For mass spectrometers, ion optics and electrode-powered systems form the electric field that controls ions. Vacuum provides the environment needed for operation. Signal detection systems are responsible for the measurement and acquisition of ion signals, while computer software and control systems are key to integrating all parts. This review started with a theoretical calculation of the time of flight mass separator, deduced an ideal formula, and provided a computer optimization to determine the required mechanical and electrical parameters. Based on the development experience in author's laboratory yearly, the review would focus on the ion optics and related electronic control technique of TOF MS, such as vertical ion beam introduction, grid-connected fields, reflectron, and etc. The ion optical technique involved the precision manufacture, and the assembly of acceleration field and reflection field. The key to the success of a time of flight mass separator was the machining precision. A good optical system should provide the ideal quality resolution. The mechanical position and shape of electrodes of the ion optical system were physically fixed after design. The other boundary condition for controlling the electric field of ion motion depended on the voltage applied to the electrodes. These voltage values were provided and controlled by the circuit power supply system. The two major components of the circuit part involved in the mass spectrometer were the signal acquisition system and the electrode power supply system, but they were not completely independent. The signal collected by the signal acquisition system should be correlated according to the timing of the electrode power supply. Finally, the computer software could convert a time-related information recorded on the acquisition card into the mass to charge ratio information of ions through the corresponding formula. © 2020, Editorial Board of Journal of Chinese Mass Spectrometry Society. All right reserved.