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Dropping baseline during oven ramp
Posted: Tue Jul 01, 2014 1:51 pm
by calvin.poh
I operate a Agilent GC-FID 7890B. The baseline recently has just rise to over 100. I have just replaced the jet of the FID detector but the problems still remain. Now normally at 120C oven temperature my baseline after 2-3 hours bakeout is still around 150, but during runs my baseline will suddenly drop gradually even the oven temperature is increasing. The baseline looks like going down stairs. Any suggestions on where the problem originate from? Carrier gas is hydrogen, without other markup gas, and compressed air from an air compressor. Peaks look fine, separation is good just the baseline is horrible. There is a big sliver universal gas trap before the GC.
Re: Dropping baseline during oven ramp
Posted: Tue Jul 01, 2014 7:15 pm
by dblux_
Remove FID insulation inside the oven and retight adapter nut.
Re: Dropping baseline during oven ramp
Posted: Sat Jul 05, 2014 2:43 pm
by Don_Hilton
Be sure you have no leaks around the inlet. If a leak opens with increasing oven temperature, flow thorugh the column will drop.
Re: Dropping baseline during oven ramp
Posted: Thu Jul 10, 2014 1:28 pm
by AICMM
calvin.poh,
If it were me, I would replace the split vent line and the trap. Odd, but I used to see this on the 5890's.
Best regards,
AICMM
Re: Dropping baseline during oven ramp
Posted: Thu Jul 10, 2014 8:06 pm
by dblux_
IMHO he/she is no longer interested in any advise. If after 10 days we have no feedback ...