Chromatography Forum

Hi, could someone please clarify in which order would N2, O2, He, N2O, CH4 and CO2 appear on TCD when using He as carrier gas and a 5A molsieve column? Thanks, Hiz

Hiz,

It is certain that you will not see He peak when using He as a carrier. I would be amazed if you did.

O2, N2, C1 would be the elution of these three peaks.

N2O and CO2 generally would not be detected as they are caught in the pores of the sieve and are eluted only with time and temperature as a flattened and distorted peak on most commercially available packings.

When I worked for Supelco I prepared MS5A packings that would allow the elution of CO2 as a symmetrical peak. I don't remember ever testing N2O on that packing, however.

best wishes,

Rod

Dear Rod,
Thanks very much for the reply that explain why I wasn't seeing a N2O peak on TCD. Given we have to use molsieve for separating O2 and N2, what would you suggest to do for measuring N2O on TCD wwhile also using molseive? The reason why we have to use TCD for N2O is we expect high N2O concentrations and we cannot dilute these as these will be collected directly from sampling bottles.

Thanks
Hiz

If I had to guess, a simple porapak Q would be as good as anything, but it might be a long one to separate CO2, and possibly subambient in temperature.

Good luck,

Rod


Gas Chromatograph Separation of Oxides of Nitrogen.

J. M. Trowell
Anal. Chem., 1965, 37 (9), pp 1152–1154
DOI: 10.1021/ac60228a021
Publication Date: August 1965

Gas chromatographic method for measuring nitrogen dioxide and peroxyacetyl nitrate in air without compressed gas cylinders

Mark R. Burkhardt , Nyengenya I. Maniga , Donald H. Stedman , Richard J. Paur
Anal. Chem., 1988, 60 (8), pp 816–819
DOI: 10.1021/ac00159a017
Publication Date: April 1988

I have an article (without attribution, sorry) by Zechmeister-Boltenstern which discusses N2O by EC and TC. I may have found it via web search. Uses Porapack QS column (along with sieve in multi-valve configuration.)

Best regards,

AICMM