SRI ECD
DETECTOR
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Detects Electronegative Compounds |
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Offers Extreme Sensitivity—down to 10ppt |
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Detects Electronegative Compounds |
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Mandated for Pesticides and PCBs |
The ECD
detector consists of a sealed 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 ( especially
chlorinated, fluorinated or brominated molecules
) such as carbon tetrachloride, bromoform, PCBs
and pesticides such as DDT enter the cell, they
immediately combine with some of the free
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 free
electrons. The pulse rate is converted to an
analog output which is connected to the data
system.
The SRI ECD
detector can be operated with either Nitrogen or
Argon/5%Methane ( P5 ) makeup gas, and Nitrogen,
P5, or helium carrier as long as the helium flow
is less than 10 ml/min. The ECD offers extreme
sensitivity ( parts per trillion for SF6 ).
Because it contains 5 millicuries of Nickel-63,
the ECD is covered by a "General License"
requiring a periodic "wipe test" and the filing
of a form with your state's Department of
Health. In most states no annual fee is
required. The ECD may be thermostatted from
ambient to 375ºC. |
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ECD
vs. DELCD |
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the ECD and DELCD detectors are useful
for halogenated analytes. The ECD
detects fluorine while the DELCD does
not. Both detectors detect chlorine and
bromine. The DELCD is much more
selective than the ECD, which detects
electro-negative molecules like oxygen
as well as halogens. The selectivity of
the DELCD can be exploited to reduce the
amount of sample preparation required.
PCBs for example can be detected by the
DELCD even in the presence of massive
co-eluting hydrocarbons. On the other
hand the DELCD is less sensitive than
the ECD, so larger amounts must be
extracted and injected on-column.
Click here
for printable ECD technical overview (.pdf).
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#SRI-8690-0020,
ECD DETECTOR |
$6,179.00 |
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