Chromatography Forum

Hi,

I am trying to analyze a gas sample containing CO2, H2, CH4 with RGA Agilent 6890 RGA with capillary column. However, there is also an unexpected N2 peak in the results almost every time. I am almost sure about sampling method or any air leak, since GC can analyze LPG without a N2 peak.

There is a possibility that moisture can be analyzed as nitrogen. It was observed that there was moisture in the samples, that comes from the excess water vapor doesn't react in the reactor. Although the gas sample is passed through silica jel, the unexpected peak is still there. Also our GC technician is concerned about moisture could damage the column and detectors.

Is anyone has any idea about the cause of this unexpected peak?

Regards,

70% of atmosphere is N2.

It is valve leak.

Wait a second. Just a nitrogen peak? If you have an air leak, you get both o2 and n2 (unless your sieve is eating O2 at really small concentrations) at about 1 to 3 ratio. Or you have an air peak that you are calling N2 (which means you are not using a sieve but something like a porous polymer.) So.... more info needed. And, by the way, the first thing I would be looking at is a leaky gas sampling valve.

Best regards,