Electron Capture Detector

Shown here is a schematic diagram of electron capture detector (ECD) for gas chromatography. The detector consists of a β-emitter, such as 63Ni. The emitted electrons ionize the mobile phase, which is usually N2, generating a standing current between a pair of electrodes. When a solute with a high affinity for capturing electrons elutes from the column, the current decreases. This decrease in current serves as the signal. The ECD is highly selective toward solutes with electronegative functional groups, such as halogens and nitro groups, and is relatively insensitive to amines, alcohols, and hydrocarbons. Although its detection limit is excellent, its linear range extends over only about two orders of magnitude.

Figure12.33

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