Discussion
Name the detector commonly employed to detect trace environmental pollutants like chlorinated pesticides, herbicides, etc. by gas chromatography :
Answer: B
The detector is the electron capture detector (ECD).
An ECD contains a radioactive source (usually nickel-63) that ionises the carrier gas to give a steady current. Molecules with electronegative atoms, especially halogens, capture electrons and reduce that current. It is therefore extremely sensitive to chlorinated pesticides such as DDT and lindane, halogenated herbicides and PCBs, at picogram levels.
Ultraviolet and refractive index detectors are used in liquid chromatography, not gas chromatography, and electrochemical detectors are mainly used in HPLC for oxidisable or reducible compounds.
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