Basic Principles of TOF Technology

The simultaneous nature of sampling ions in TOP offers distinct advantages over traditional scanning (sequential) quadrupole technology for ICP-MS applications in which large amounts of data need to be captured in a short span of time. To understand the benefits of this mass separation device, let us first take a look at its fundamental principles. All TOP mass spectrometers are based on the same principle the kinetic energy (KE) of an ion is directly proportional to its mass (m) and velocity (VO. This can be represented by the following equation  

Therefore, if a population of ions—all with different masses—is given the same KE by an accelerating voltage (U), the velocities of the ions will all be different, depending on their masses. This principle is then used to separate ions of different mass-to-charge ratios (m/e) in the time (0 domain over a fixed flight path distance (D), represented by the following equation  

Practical Guide to ICP-MS A Tutorial for Beginners, Second Edition 

FIGURE 9.1 Principles of ion detection using time-of-flight technology, showing separation of three different masses in the time domain. 

FIGURE 9.2 A schematic of an orthogonal acceleration TOF analyzer. (From Technical Note 001-0877-00, GBC Scientific, February 1998.) 

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