QUICKLY UNDERSTAND ELECTRON IONIZATION (EI Explained For Beginners)

Electron ionization (EI), also known as electron impact ionization and even electron bombardment ionization, is an ionization method where high energy electrons interact with other atoms or molecules in solid or gas phases to produce ions. It is considered a hard ionization method because it uses high-energy electrons which causes high fragmentation. In other words, the ionized molecules often break into their smaller constituent parts. Let us take a closer look at electron ionization in action! First, the sample can enter through the sample inlet here. Then under high vacuum conditions, a current is applied to the filament to emit electrons, and these electrons are accelerated from the filament to the electron receiving end or the trap electrode which removes them to maintain a stable ion current. In this process, the electrons collide with the sample molecules, causing the sample molecules to ionize or fragment. In other words, the sample atoms or molecules lose electrons turning them into positive ions or molecular ions. These molecular ions continue to be bombarded by electrons, breaking some of the chemical bonds, which is what causes the fragmentation. Then the repeller uses its positive charge to cause these positive ions to exit the ionizer. If you like the video so far, please give it a quick like! The pros of electron ionization include the following: 1. EI is non-selective and any sample which can be vaporized can be ionized 2. EI has high ionization efficiency and sensitivity 3. EI spectrum provides a wealth of structural information and is called the “fingerprint” of the compound, not to be confused with fingerprinting also used sometimes in mass spectrometry The cons of EI include: 1. Not suitable for volatile and thermally unstable samples 2. Some compounds are fragile in EI mode and do not give an accurate mass spectra 3. EI method can only detect positive ions and does not detect negative ions Electron ionization was one of the earliest ion sources for mass spectrometry and is still used today, mainly in combination with GC-MS. It can be used for the: - analysis of biological fluids - elemental analysis of organic species - pesticide residue analysis