Chromatography Forum

I am using a Shimadzu methanizer MTN-1 with a GC-2010. When we switch off the methanizer or change the carrier to helium, we have good baselines. However, when the methanizer is on, the baseline looks horrible, it will register percent level, but the baseline is so bad, it will not register ppm level (which is what I need) I have changed the Nickel catalyst and am running out of ideas, I was wondering if anyone had suggestions.

Assuming the catalyst is good, then you probably have contamination.

Finding the source is the problem.

If the source has been corrected then there may still remain contamination in the tubing or the methanizer or in the column or connecting parts.

Find an oven you can back out the methanizer at 400°C with a carrier of hydrogen to renew the catalyst.

If your catalyst support is based on silica then you should be able to oxidize any carbon present by baking at high temperature with air as the carrier.

An FID reacts to carbon primarily but silicon and other elements can be sensed by the detector. If you were having an air leak into the methanizer then you can be creating water which can give you an unstable baseline.

Eliminate the source of contamination.
Properly condition your catalyst tube.
Use clean gases and you should be fine.

good luck,

Rodney George
consultant

I am using a Shimadzu methanizer MTN-1 with a GC-2010. When we switch off the methanizer or change the carrier to helium, we have good baselines. However, when the methanizer is on, the baseline looks horrible, it will register percent level, but the baseline is so bad, it will not register ppm level (which is what I need) I have changed the Nickel catalyst and am running out of ideas, I was wondering if anyone had suggestions.

Probably you have bad catalyst powder. Try to bake the nikel unit for some time to see it's getting any better before replacing it.