NGA GC

Question

We use NGA GC with Hayesep Q Pre column and 10 ft analytical column along with Molsieve 13X column. The molsieve column doesnt show the peak of Oxygen during the Molsieve elution. Also a peak co-elute with Hydrogen sulfide during the Hayesep Q column elution. Kindly advise how to rectify this problem.

Dr. Know · Answer

Hi bijishnair, 
 an analyzer is a finely tuned instrument and some things in analyses can happen if it wasn't tuned to it. So, my answer is about the columns and their interactions only. And not leaks in your system. 
 Firstly, oxygen absorption by the porous polymer phase can happen if the oxygen concentration is very low (<50 ppm). Porous polymers contain free radicals in their chemical structure that can bind oxygen (oxidation of the polymeric phase, but not a lot). What could help is one or more injections of air (=20% O2), then all free radicals are saturated for quite some time. 
 Secondly, the H2S. Water elutes very close to H2S and may be that interfering peak. 
 Regards, 
 Norbert

NGA GC

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