Chromatography Forum

I have a Varian 3800 GC with a TCD detector. The column is a Haysep column (Grace Davison 2836PC).

The initial column T is 35. At 15 minutes, the column temperature is programmed to increase and the baseline decreases slowly with time. When the temperature reaches around 140, the baseline begins to increase gradually until the final column oven temp (220) is reached. This is not the problem. The problem is that in the rising baseline portion of the program, there are a number of "peaks". These peaks are essentially vertical on the leading edge and tail very slowly. They are fairly consistent, though there is some drift with time and height.

What would be causing this?

Thank You

Several possibilities

First problem: baseline drop with temperature increase. Not good. Sounds like a leak in the system. Air can damage polymer.

Baseline increase with temperature increase. Expected unless you have the flow carefully controlled. If controlled by constant pressure, flow will decrease with temperature increase with baseline increase from the drop in flow rate.

Vertical broad, slowly tailing peaks. Suggests reaction is occurring, not trapped peaks, unless the peaks are large in which case it may be trapped from contaminants from the carrier or from deposits of previous injections.

A chromatogram would be helpful and well as a column use history.

best wishes,

Rod

Thank you very much. Armed with your advice, I checked for leaks and found one in the reference gas line. I fixed that, and the issue is resolved. Again, thank you.