I am looking to run % levels of ammonia, oxygen, and propane gases by GC. Although a TCD is considered a "robust" detector, I was wondering if there would be any problems using this detector with ammonia.
I already have a column in mind (Supleco HayeSep) that can handle % ammonia and will be using a gas sampling valve for on-line analysis. Anything else I should consider with ammonia?
By Bill Jenko on Wednesday, February 14, 2001 - 08:42 pm:
Virtually any TCD should work fine at normal operating temperatures. Most TCDs use Tungsten/Rhenium filaments that will not be much affected by small samples (<1mL) of Ammonia or Oxygen. Moreover, even if you do blow a detector over a period of years, they are relatively easy and cheap to replace or repair.
Ammonia seems to react with stainless steel and the packing. Depending on your ammonia concentrations and size of sample, you may see significant tailing of the ammonia peak, and it can take some time to "saturate" the system to get a constant response. Glass or fused silica columns are good. Silcosteel is generally not recommended, but might work well under some conditions.
PS: You can also use a PID for ammonia at trace levels, provided the lamp has about 10.2 eV, but it is not easy. I always wanted to try a Hall (electolytic conductivity detector) in its N2 or Sulfur mode for trace ammonia, but have never done so. Despite the name, NPDs (aka TSDs) do not measure ammonia. FIDs don't work either.
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