Biochemical Techniques and Instrumentation

2.6.3.6.2. Electron Capture Detector (ECD)

Electron capture detector is a highly selective detector, since only compounds with an affinity for electrons can be detected. It consists of a chamber with an inlet and outlet for column effluents. The inlet is provided with positive electrode (cathode) and outlet with a negative electrode (anode). The cathode side is also provided with a radioactive tritium or nickel foil (Nickel–63). Nickel-63 emits energetic electrons which collides with carrier gas, nitrogen and produce more electrons and create a small but steady current of electrons to flow across the electrodes. When the sample components with carrier gas pass into the chamber, it captures some of the electrons passing from cathode to anode. This reduces the steady current between the two electrodes, which is then amplified and recorded to give the chromatogram. It is most commonly used for halogenated organic compounds such as insecticides.

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