What are the four stages of mass spectrometry?

Mass spectrometry is used to accurately measure the mass of the various molecules within a sample. The four stages of mass spectrometry are – ionization, acceleration, deflection, and detection.

1. Ionization: The sample is vaporized before being passed into an ionization chamber where it is bombarded by a stream of electrons emitted by an electrically heated metal coil. The forceful collisions knock off one or more electrons from the particle, resulting in a positively charged ion. Most of these have a +1 charge because of the inherent difficulty in removing a second electron from an ion that is already positive.
2. Acceleration: The positively charged ionization chamber repels the positively charged ions, which accelerate towards three negatively charged slits with progressively decreasing voltage. The speed at which they accelerate depends on their mass so the lighter ions move faster than the heavier molecules.
3. Deflection: In this stage, the stream of positively charged ions are deflected by a magnetic field. The extent of the deflection depends on the mass and charge of the ion. The lighter the mass of the ion, the more the deflection. Ions with a charge greater than +1 will also be deflected more.
4. Detection: In this final stage, the beam of ions passing through the mass analyzer is detected by a detector on the basis of the mass-to-charge ratio (m/z). When an ion hits the detector, the charge is neutralized by an electron jumping from the metal onto the ion. This generates an electrical current which is proportional to the abundance of the ion. The mass spectrum generated on completion of these four stages is sent to a computer for analyses, where it shows the different m/z values of the ions present and their relative abundance.