Photo-ionization detector

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A photo-ionization detector (PID) is a type of detector used in gas chromatography.

[edit] Principle

A PID is an ion detector which uses high-energy photons, typically in the UV range, to produce ions. As components elute from the GC's column they are bombarded by high-energy photons and are ionized. 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

PIDs are highly selective detectors. They will only detect components which have ionization energies similar to the energy of the photons the detector uses. This selectivity can be useful when analyzing mixtures in which only some of the components are of interest.

PIDs 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.

[edit] External links

• OI Analytical A maker of PIDs
• Library 4 Science Further Chromatography Reading
• Chrom Forum Discussion forum for chromatography; has a "Student Projects" section for beginner's questions

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