What is Flame ionization detector?
'''Flame Ionization Detectors''' (shortened FID) is a common type detector used in [[gas chromatography]]. These detectors are best at detecting [[organic compounds]]. The first flame ionization detector was developed in simultaneously and independently in 1957 by Harley and Pretorius at the [[University of Pretoria]] in Pretoria, [[South Africa]] and by McWilliam and Dewar at Imperial Chemical Industries of Australia and New Zealand (ICIANZ, see Orica history) Central Research Laboratory, Ascot Vale, Melbourne, Australia. The purpose of a FID is to detect compounds as they exit the gas chromatography column. The compounds that are exiting the column are in a gaseous state. Detection is done by first turning the gas compounds into ions and electrons and then collecting the charged molecules. The FID turns compounds into ions and electrons by putting them into a flame. The fuel used to make the flame in FIDs is usually made of a mixture of hydrogen and [[oxygen]]. As these charged materials are collected, they make a current which is measured. The larger the current the more charged compounds are being collected. Currents for FIDs are usually about 10<sup>-12</sup> amps and are measured by a [[high-impedance picoammeter.]] Flame ionization detectors are used most often for organic compounds. This is because organic compounds contain lot of carbon atoms which easily turn into ions. Reduced carbons (carbons with no oxygen bonds) make the most ions. Other carbons such as [[Alcohol|alcohols]] (C-O-H) and [[Carbonyl|carbonyls]] (C=O) do not make as many ions. Many times organic samples being tested are not pure. The samples often contain impurities such as [[water]] (H<sub>2</sub>O), [[carbon dioxide]] (CO<sub>2</sub>), [[sulfur dioxide]] (SO<sub>2</sub>), [[Nitrous oxide|nitrous oxides]] (NO), and [[Noble gas|noble gases]]. The FID does not detect these impurities because they do not burn. This makes the FID a very useful detector because the samples being tested do not have to be purified before being tested. FI