2. Standards

Standards, whether in solid or gaseous form, are reference standards whose concentrations and isotopic composition in rare gases are perfectly known. Connected to a UHV purification line, they are used to determine the sensitivity of mass spectrometers for each of the isotopes analyzed, which is usually expressed in amperes per torr and represents the analyzer's ability to detect a known quantity of gas. Its value, between 10 ^–5 and 10 ^–3 A · ^{– torr 1} depending on the source parameters, is essential for calculating gas concentrations in a sample.