Helium ionization detector
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A helium ionization detector (HID) is a type of detector used in gas chromatography.
[edit] Principle
An HID is an ion detector which uses a radioactive source to produce ions. The radioactive source ionizes helium atoms by bombarding them with emissions. As components elute from the GC's column they are mixed with the helium ions, which then ionize the components. The ions produce an electric current, which is the signal output of the detector. The greater the concentration of the component, the more ions are produced, and the greater the current.
[edit] Application
HIDs are sensitive to a broad range of components. They must use helium as a carrier gas.
HIDs are non-destructive detectors. They do not destroy/consume the components they detect. Therefore they can be used before other detectors in multiple-detector configurations.
The drawback to HIDs are that they contain a radioactive source. In the U.S., this means they fall under a number of federal regulations concerning their use in the workplace, shipping, disposal, etc. Discharge ionization detectors have generally supplanted them.
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