flow pulsing!!

[che313]

in our gc we set the flowrate of He gas to be 1.4ml/min but after around 0.8 min after injection the sample it is pulsed to 1.5ml/min!! I replae the liner, septa and cutting aroun 30cm from colum @ injection port but not succeded in solve it.

[Don_Hilton]

Split or splitless?
What solvent and what liner volume?
What GC? - flow controler could be important.

[che313]

splitless
methanol
agilent 6890N
we were useing the gc for 4 years, this is just begin last week

[aldehyde]

Do you have any sort of trap on your helium line? Moisture can adsorb onto the frits in the electronic pressure controller and cause this symptom. Do you have any sort of flow meter?