Scientific Equipment Source
4-555 Wentworth Street East
Oshawa, ON, L1H 3V8
Canada
Tel: 905-231-0930
Fax: 905-231-0944

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ECD detector, Agilent 6890

The electron capture detector (ECD) cell contains 63Ni, a radioactive isotope emitting high energy electrons (Boparticles).These undergo repeated collisions with carrier gas molecules, producing about 100 secondary electrons for each initial Boparticle.

Further collisions reduce energy of these electrons into the thermal range. These low energy electrons are then captured by suitable sample molecules, thus reducing total electron population within the cell.

Uncaptured electrons are collected periodically by applying short term voltage pulses to cell electrodes. This cell current is measured and compared to a reference current, and the pulse interval is then adjusted to maintain constant cell current.

Therefore, pulse rate (frequency) rises when an electron capturing compound is passing through the cell. The pulse rate is converted to a voltage, linearly related to amount of electron capturing material in the cell.

Thus, the ECD responds to compounds having an affinity for electrons (for example, such halogenated materials as pesticides and related compounds).

General indication of expected sensitivity to different classes of organic compounds.

Chemical Type

Sensitivity

Hydrocarbons

1

Ethers, esters

10

Aliphatic alcohols, ketones, amines; mono-Cl, mono-F compounds

100

Mono-Br, di-Cl and di-F compounds

1000

Anhydrides and tri-Cl compounds

10-4

Mono-I, di-Br and nitro compounds

10-5

Di-I, tri-Br, poly-Cl and poly-F compounds

10-6

These are only approximate figures; sensitivity varies widely within each group, depending upon structure of the material. For example, DDT (5 chlorine atoms/molecule) can be measured in the 1 to 10 picogram range.

The ECD is designed for use either with N2 or with 5% CH4 in Ar as carrier gas. A switch selects operation with either carrier gas; the ECD does not operate properly if the switch is incorrectly set. Because of its high sensitivity, the ECD should never be used without traps (moisture, chemical), should be in good condition, and should be installed in the carrier gas supply line. For capillary systems, this must also be done for the makeup gas supply.

An ECD is normally used to detect compounds that are reactive enough to interact with metal columns. Therefore, only " packed glass, or fused silica, or glass capillary columns are recommended with this detector.

 

If you are a bargain hunter please give us a call, we always have instruments in stock, which have not been refurbished and can be sold as is in working condition.

Scientific Equipment Source provides service and training on site in most of central Ontario this includes neighboring cities Ajax, Whitby, Pickering, Oshawa, Toronto, Mississauga. We can also provide training and courses on site on chromatograph (GC), HPLC in the Durham region; this includes Pickering, Ajax, Whitby, Oshawa. For other customers we can be also flexible on arrangements. For the rest of customer any equipment for repair has to be sent back by a courier.