Chromatography Forum

we are using varian GC 3800 to analyze our sample for H2 with TCD. Normally its 1000 ppm. but suddenly one day we got 45 ppm and peak size also was reduced. then i run stndard 3000 ppm i got same 46 ppm and same size of peak.i run blank(N2) still there was peak at Retention time of H2 with same 46 ppm. one observation is that we are also using FID in this mathod there is also no peak at all for other streams and base line abnormal. we assumed that there is some problem with the column either contaminated or some thing else. need your advise we are using molsive column.

Thnx

Are you certain you are using nitrogen carrier for your TCD train?

Did you accidentally hook up the wrong gas? or get the wrong gas in your cylinder?

This is most likely cause.

best wishes,

Rod

Yes Rod u r right by mistake operation they sent wrong sample with little higher moisture.Yes we are using N2 .So we have to change column in any case?? even though we put column on higher temperature.

Using a DRY carrier gas, heat the column (in GC or in another oven) slowly up 60°C to 200°C and hold for 12 hours.

By slowly I mean over a period of 4-8 hours but at the fastest flow rate you can afford.

best wishes,

Rod

Thanx dear