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GCDetectors
ECD - ElectronCaptureDetector
• DetectsElectronegativeCompounds
• OffersExtremeSensitivity - down to10ppt
• Thermostatted fromAmbient to375°C
• Mandated for Pesticides andPCBs
The SRI ElectronCaptureDetector can be operatedwith either nitrogen
or argon-5% methane (P5) makeup gas, and nitrogen, P5, or helium
carrier (as long as the helium low is less than 10milliliters per minute).
TheECDmay be thermostatted from ambient to375°C.
The ECD detects electronegative compounds, especially chlorinated,
luorinated, or brominated molecules such as carbon tetrachloride,
bromoform, PCBs andpesticides such asDDT. The ECD offers extreme
sensitivity (parts per trillion for SF
6
).
The ECD consists of a stainless steel cylinder containing
radioactive Nickel-63. The Nickel-63 emits beta particles
(electrons) which collide with the carrier gas molecules, ionizing
them in the process. This forms a stable cloud of free electrons
in the ECD cell. When electro-negative compounds enter the
cell, they immediately combine with some of the electrons,
temporarily reducing the number remaining in the electron cloud.
The detector electronics, which maintain a constant current (of
about 1 nanoampere) through the electron cloud, are forced to
pulse at a faster rate to compensate for the decreased number
of freeelectrons. Thepulse rate is converted toananalogoutput,
which is connected to thedata system.
Because it containsonly5millicuriesofNickel-63, theECD iscoveredbya “general license,”which requires
aperiodicwipe test and theilingof a formwithyour state’sDepartment ofHealth. Inmost states, noannual
fee is required.
8690-0020
ECDdetector
