Electron capture detector
2606066
215335828
2008-05-27T19:23:43Z
DOI bot
6652755
Citation maintenance. You can [[WP:DOI|use this bot]] yourself! Please [[User:DOI_bot/bugs|report any bugs]].
The '''electron capture detector''' (ECD) was invented in [[1957]], by [[James Lovelock|Dr. James E. Lovelock ]].<ref>
{{cite journal
| title = A sensitive detector for gas chromatography
| author = J. E. Lovelock
| journal = Journal of Chromatography A
| year = 1958
| volume = 1
| issue = 1
| pages= 35–46
| doi = 10.1016/S0021-9673(00)93398-3
}}</ref> It is a device for use in [[Gas-liquid chromatography|gas chromatography]] that can detect tiny amounts of chemical compounds in the atmosphere and elsewhere. The electron capture detector is used in detecting electron-absorbing components in the output stream of a [[gas chromatograph]].
The ECD uses a radioactive [[Beta particle]] (electrons) emitter -- a typical source contains a metal foil holding 10 milli[[curie]]s of Nickel-63. The electrons formed are attracted to a positively charged [[anode]], generating a steady [[Electric current|current]]. As the sample is carried into the detector by a stream of [[nitrogen]] or a 5% [[methane]], 95% [[argon]] mixture, analyte molecules capture the electrons and reduce the current between the collector anode and a [[cathode]]. The analyte concentration is thus proportional to the degree of electron capture, and this detector is particularly sensitive to [[halogen]]s, organometallic compounds, nitriles, or nitro compounds.
==Sensitivity==
The ECD is 10-1000 times more sensitive than an [[Flame ionization detector|FID]], and one million times more sensitive than a [[Thermal conductivity detector|TCD]], but has a limited dynamic range and finds its greatest application in analysis of halogenated compounds. The detection limit for electron capture detectors is 5 femtograms per second (fg/s), and the detector commonly exhibits a 10,000-fold linear range. This made it possible to detect halogenated compounds such as pesticides and [[CFC]]s, even at levels of only one part per trillion ([[Parts_per_notation|ppt]]), thus revolutionizing our understanding of the atmosphere and pollutants.
==References==
<div class="references-small"><references/></div>
==Reviews==
*{{cite journal
| title = Selective detectors in gas chromatography
| author = M. Krejči and M. Dressler
| journal = Chromatographic Reviews
| year = 1970
| volume = 13
| issue = 1
| pages= 1–59
| doi = 10.1016/0009-5907(70)80005-9
}}
*{{cite journal
| title = Electron capture detection in gas chromatography
| author = E. D. Pellizzari
| journal = Journal of Chromatography A
| year = 1974
| volume = 98
| issue = 2
| pages= 323–361
| doi = 10.1016/S0021-9673(00)92077-6
}}
*{{cite journal
| title = The electron capture detector
| author = J.E. Lovelock
| journal = Journal of Chromatography A
| year = 1974
| volume = 99
| issue = 1
| pages= 3–12
| doi = 10.1016/S0021-9673(00)90840-9
}}
[[Category:Measuring instruments|Electron Capture Detector (ECD)]]
[[Category:Gas chromatography]]
[[de:Elektroneneinfangdetektor]]
[[es:Detector de captura de electrones]]