Many

gas chromatograph Gas chromatography (GC) is a common type of chromatography used in analytical chemistry Analytical chemistry studies and uses instruments and methods to separate, identify, and quantify matter. In practice, separation, identification or qua ...

detectors are

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...

detectors with varying methods of ionizing the components eluting from the gas chromatograph's column. An ion detector is analogous to a

capacitor A capacitor is a device that stores electrical energy in an electric field by virtue of accumulating electric charges on two close surfaces insulated from each other. It is a passive electronic component with two terminals. The effect of a ...

vacuum tube A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric voltage, potential difference has been applied. The type kn ...

. It can be envisioned as two metal grids separated by air with inverse charges placed on them. An electric potential difference (voltage) exists between the two grids. After components are ionized in the detector, they enter the region between the two grids, causing current to pass from one to the other. This current is amplified and is the signal generated by the detector. The higher the concentration of the component, the more ions are generated, and the greater the current. Some early FIDs actually used two metal grids as their ion detectors. However, more efficient designs have been developed, so few current ion-type detectors use two metal grids. But the principle is the same, and it can be easiest to think of the detector in this manner.

Types of Ion Detectors

Flame ionization detector A flame ionization detector (FID) is a scientific instrument that measures analytes in a gas stream. It is frequently used as a detector in gas chromatography. The measurement of ion per unit time make this a mass sensitive instrument. Standa ...

(FID) -- uses a flame to produce ions *

Electron capture detector An electron capture detector (ECD) is a device for detecting atoms and molecules in a gas through the attachment of electrons via electron capture ionization. The device was invented in 1957 by James Lovelock and is used in gas chromatography to ...

(ECD) -- uses

beta radiation A beta particle, also called beta ray or beta radiation (symbol β), is a high-energy, high-speed electron or positron emitted by the radioactive decay of an atomic nucleus during the process of beta decay. There are two forms of beta decay, β� ...

Photo-ionization detector A photoionization detector or PID is a type of gas detector. Typical photoionization detectors measure volatile organic compounds and other gases in concentrations from sub parts per billion to 10 000 parts per million (ppm). The photoionization ...

(PID) -- uses

UV light Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...

to produce ions * Helium ionization detector (HID) -- uses a radioactive source to produce helium ions, which in turn ionize the components * Discharge ionization detector (DID) -- uses an

electric spark An electric spark is an abrupt electrical discharge that occurs when a sufficiently high electric field creates an ionized, electrically conductive channel through a normally-insulating medium, often air or other gases or gas mixtures. Michael ...

source to produce helium ions, which in turn ionize the components * Pulsed discharge ionization detector (PDD) -- similar to a Discharge ionization detector (DID), but uses a different sort of spark

References

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Types of Ion Detectors

References

See also