Elektroniionisaatio

Elektroniionisaatio, also known as electron ionization or EI, is a common method of ionization used in mass spectrometry. In this process, a sample is bombarded by a beam of energetic electrons. These electrons strike the atoms or molecules of the sample, knocking out one or more electrons from them. This results in the formation of positively charged ions, often referred to as molecular ions.

The energy of the electrons used in EI is typically around 70 electron volts (eV). This energy is sufficient to cause ionization but is generally not high enough to cause significant fragmentation of the molecule, although some fragmentation can occur. The fragmentation pattern produced by EI is often characteristic of the specific molecule, making EI a useful tool for identifying unknown compounds.

The ions produced by EI are then separated and detected based on their mass-to-charge ratio. The resulting spectrum, known as a mass spectrum, displays the relative abundance of each ion. This spectrum serves as a fingerprint for the analyzed substance.

EI is a relatively straightforward and inexpensive ionization technique, making it widely used in many analytical applications, particularly in organic chemistry and environmental analysis. However, it is generally only suitable for volatile and thermally stable compounds, as the sample needs to be introduced into the gas phase under vacuum conditions.