Discharge ionization detector
Encyclopedia
A discharge ionization detector (DID) is a type of detector used in gas chromatography.
which uses a high-voltage electric discharge
to produce ion
s. The spark ionizes helium
atoms that are mixed with components as they elute from the GC's column, causing the components to become ionized. The ion
s 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.
DIDs 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.
DIDs are an improvement over Helium ionization detector
s in that they contain no radioactive source.Figure should be included.
Principle
A DID is an ion detectorGC ion detector
Many GC detectors are ion detectors with varying methods of ionizing the components eluting from the GC's column.-Principle of Operation:An ion detector is analogous to a capacitor or vacuum tube. It can be envisioned as two metal grids separated by air with inverse charges placed on them. An...
which uses a high-voltage electric discharge
Electric discharge
Electric discharge describes any flow of electric charge through a gas, liquid or solid. Electric discharges include:*Electric glow discharge*Electric arc*Electrostatic discharge*Electric discharge in gases*Leader *Partial discharge...
to produce ion
Ion
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...
s. The spark ionizes helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...
atoms that are mixed with components as they elute from the GC's column, causing the components to become ionized. The ion
Ion
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...
s produce an electric current
Electric current
Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...
, 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.
Application
DIDs are sensitive to a broad range of components.DIDs 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.
DIDs are an improvement over Helium ionization detector
Helium ionization detector
A helium ionization detector is a type of detector used in gas chromatography.-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...
s in that they contain no radioactive source.Figure should be included.