Chromatography Forum

Hello everyone,

It is the first time I use this kind of forum, so excuse me if it is not appropriate or if my english is not so good.
I'm using a Agilent GC 7890B with a purge and trap system and a capillary column. Recently, the GC do not turn in "ready" and remains on "not ready" state. When I check the status, the Aux EPC1 pressure is not ready. It is the pressure into the column that is too high. And it trends to rise with time.
But, even if it is not ready, if I launch a run, the pressure goes down to the value expected.

I already cut off like 1m of my column in case of there is a plug (blockage) into it but it doesn't seem to change anything. I rise the oven temperature till 275°C to eliminate what it may be inside. And it seems that there is a blockage because when I launch the purge, the pressure doest not go down when I stop it.
Of course, I cleaned everything that I could before doing all this.

If you have any ideas or solutions or whatever, it could be well appropriate !

Thank you,
Colin

You need to split this problem into two parts, is it the GC or the purge and trap causing the problem. The fact that you mention that the pressure is OK when you start the system, suggests to me that the problem could be in the purge and trap. When you start, perhaps a valve actuates in the purge and trap which switches the carrier gas through a different path.

If you are supplying gas from the GC into the purge and trap, and then there is an output from the purge and trap back into the GC, try connecting these two lines so that the purge and trap is NOT in the gas flow. This will tell you if the problem is the GC or the purge and trap.

Gasman

If it is in the GC, check your split vent.
If it is in the concentrator, check the trap and the 6 port valve.

What manufacturer is the Purge and Trap?

Is the transfer line connected to a split/splitless inlet on the 7890 or is it using the Volatiles interface?

If it is going to a split/splitless inlet, are you running in split or splitless mode? Mode should be split and at least 20:1 split ratio, higher is better.

Have you tried to inject a standard into the inlet (if possible) and see if you have a good chromatogram? If the chromatogram is good then the problem is not the column but something else is impeding the flow.

Was the system working before, and if so was maintenance done recently?