Helium ionization detector

{
  "id": "MLC-T-CHM-005165",
  "term": "Helium ionization detector",
  "field": "Chemistry",
  "definition": "A gas chromatography detector in which a weak beta radiation source and an applied voltage raise helium carrier-gas atoms to a metastable state. These excited atoms ionize any eluting substance with an ionization potential below roughly 18 eV, and the resulting current measures the components. It is mainly used for inorganic gases at about 0.1 to 10 ppmv, and it needs very pure helium and a leak-free system.",
  "subject": "Chemistry and the Environment",
  "see_also": [
    "carrier gas",
    "linear range",
    "unstable"
  ],
  "references": [
    "PAC, 1990, 62, 2167. 'Glossary of atmospheric chemistry terms (Recommendations 1990)' on page 2191 (https://doi.org/10.1351/pac199062112167)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/helium-ionization-detector/"
}