Chromatography Forum

Hello
We are working on noble gases. Trying to detect krypton (0.1% krypton in nitrogen) using GC-TCD (GC - 17A Shimadzu) with CP-Molecule sieve, capillary column, 50 m X 0.53 mm. The operation condition of GC was set as: Carrier gas flow (Helium) – 3 - 4 mL/min; Oven Temp: 40 C for 5 min then 24 C/min for 225. Inlet Temp: 100 C, Detector Temp: 80 C, makeup gas flow - 10 mL/min; Also we were work on 30 C for Isothermal. But I have not found a krypton peak. Does anyone have an idea which column and condition would be suitable to detect the krypton or separate nitrogen and krypton by GC?
Thank you.

The only column that you can use is a molecular sieve column. If you are looking for Krypton in nitrogen it is possible that the krypton is hidden in the tail of the nitrogen peak. You could try using nitrogen as the carrier gas, then you you will not get a huge nitrogen peak and 0.1% Krypton should be detectable.

Gasman

Agreed about nitrogen carrier as the separation between nitrogen and krypton is minimal, and the nitrogen matrix peak will have a big tail on it. You will need a large injection volume, and you'll need to increase gas flow I would say to sharpen your peaks as much as possible. There is a bit of a difference in thermal conductivity though so you will get a response. You want to set the TCD for as high a filament current as nitrogen carrier will allow.