Chromatography Forum

Hi,
I was using packed moleshieve column before and I was able to separate oxygen and nitrogen. Now I change the column to Carboxen 1010 Plot porous layer open tubular capillary column by Supelco, but I am not able to separate oxygen and nitrogen. I am using Argon as my carrier gas. the GC is GC-14B by Shimadzu. Please suggest. Thanks.

First, what was the purpose of switching?
Second, is there a reason for using argon as a Carrier Gas (I'm assuming this is a TCD instrument). Argon is such as large atom, try He instead, or even better, Hydrogen.
More suggestions could be made if more was know about thie instrument and the method conditions.

Hope this helps
Will

The Carboxen 1010 column can not baseline resolve Argon and Oxygen. If the detector is a TCD, it sees Oxygen as part of the Argon carrier gas flow and is subtracted out when compared to the Argon flow through the reference side of the detector.

I would change the carrier gas to Hydrogen (or Helium if you are concerned about the unlikely danger of a Hydrogen explosion). If changing the carrier gas is not possible, then you really need a column that will separate Argon, Oxygen and Nitrogen. Molesieve 5A is really the best for this.

Bill

YOu may be able to almost baseline resolve oxygen and nitrogen using the carb-1010 column, if the concentrations are low and if you can get the GC cold enough. The argon is a problem, as others have posted, you're going to change.

The Carboxen column is supposed to be much less susceptible to polar impurities than the traditional columns. We switched a year ago on one instrument after a horrible carrier gas problem. We've been cautiously optimistic that this is a good alternative.

I may be missing something here but I would argue that argon carrier is a great choice. You know you cannot separate argon from oxygen so why not just make the argon part of the sample blend in with the carrier. Even if the argon is contaminated with oxygen, the reference side of the bridge accounts for that and all you are measuring is the difference in oxygen between the injected sample and the carrier. Assuming, of course, that the oxygen in the sample is at a high enough concentration to measure using argon carrier (poor thermal conductivity differential and all....) I have not used carboxens so I cannot help with the oxygen/nitrogen issue except to say you should think about a valve or cryo as starting points.

Best regards.

I use this column too. Initially, I had difficulty in separating oxygen and nitrogen but after developing a proper method, it has never been an issue. Argon is the right carrier gas.
Follow this method:
Oven
Inital temperature at 32 C for 12 min (this long wait is to see teh separation between oxygen and nitrogen) then ramp at 30 C/min till it reaches at 236 C to remove CO, methane and CO2.

Well, again the procedure would depend on what dimensions your column is. I m using a 30 m long column with a nominal diameter of 320 um and a film thickness of 15 um.

Also, I have a ramped flow rate. It is initially kept at 0.4 ml/min for 12 min and then ramped at 0.1 ml/min2 till the flow reaches 0.4 ml/min.

Also, I use very small sample size (100 ul) and have a split ratio of 30:1.

Hope this helps you. Feel free to ask questions if you have any doubts.

Karthic

Hello everyone

I just joined the forum.
Please help me about the new column..Carboxen-1010
I install it in GC6890 Agilent
It seems that no peak of O2 and N2 were detected with Argon as a carrier gas.
How about the ref gas? What is the most suitable? compressed air or helium and what is the flowrate?

please help