We are analysing samples for N2/Ar ratios using a modified version of the An and Joye (1997) method: He carrier gas, stripping and cryogenic trapping of gases, Ca-chabazite packed column at 30C, GC-TCD.
We are seeing two peaks, rather than the expected three (Ar, O, N2): the first peak seems to be a combination of Ar and O; the second peak is N2. Because this method requires a ratio between N2 and Ar, we must separate the Ar and O peaks.
Are there any suggestions for how to 1) increase/obtain peak separation of Ar and O (e.g., via modification of oven/detector temperature, carrier flow rate, ?) or 2) remove oxygen (but not Ar and N2) from the sample after cryogenic trapping?
Any assistance will be much appreciated!
By MC Schwartz on Monday, May 31, 2004 - 12:38 am:
We have had some subsequent success in separating the Ar and O peaks by baking the column at 380-400 deg C for 12-24 hours (i.e., following the initial conditioning protocols outlined in An and Joye (1997) and Maroulis and Coe (1989)).