|
The
Methanizer consists of a 6" x 1/8" stainless steel tube which is mounted
alongside the edge of the heated valve oven, and thermostatted to 380ºC.
The tube is packed with a special nickel
catalyst powder.
Column effluent is mixed with 20 ml/min of hydrogen just prior to the methanizer
entrance. Under these conditions, CO and CO2 are converted to methane
while passing through the methanizer. Hydrocarbons such as ethane,
propane, etc. pass through the methanizer unaffected. Because the
CO and CO2 are converted to methane, they can be detected by the FID down
to 1 ppm, whereas the TCD can only detect CO or CO2 at 100 ppm at best.
Detection limits are thus
improved by
a factor of 100. It is important to remember that the methanizer
is located after the
column ( and
usually after the TCD detector ), so the CO and CO2 peaks pass through
the column and TCD cell as CO or CO2. They are not converted to methane
until they exit the column and TCD, so the retention times are not affected.
The methanizer can not be mounted unless the GC is already configured with
a valve oven. Methanizer tubes can be poisoned by large amounts of
sulfur gas.
8690-0081 Methanizer accessory mounted
on 8610C GC $ 995.00
8690-1081 Replacement methanizer tube
$ 100.00 |
|
