Chromatography Forum

Hi,

We are currently having issues with our Agilent 6890 GC/MS in that it will show "waiting for GC ready" for 30 minutes before injecting a sample. We have a GC cool down of 10 minutes in between runs but it is waiting a lot longer than that. As far as I know, it only really happens with one method that is being used and the girl that is running it has made a new one but it is still paying up. Has anyone had this problem before or know of any ways that we can possibly fix it?

Thanks
~Jo

"waiting for GC ready" is what Chemstation says? What does the front panel say when you hit the "status" button? Maybe it says oven temp, or front inlet pressure? Is there a 20 minute oven equilibration time plugged into the method somewhere on accident?

Hi Jo,

I would be inclined to check that you have programmed in the cooldown temperature program otherwise it will just cool down at the default setting.
Actually it would be really helpful if you could cut and paste the method parameters into your email.

cheers
Liz

Hi guys,

Thanks for your quick replies.

Now to reply to you...

Schmitty: Yes, "waiting for GC ready" is what Chemstation says. When I press the status button on the GC it says "oven temp". There is not a 20 minute cool down by accident.

Liz: I am not sure what you mean by cool down at the default setting. Does this mean that it will cool down and take as long as it wants to get to the desired temperature?

The temperature program starts at 35C for 1.5min, 7C/min to 245C hold 3.5minutes. I am not sure but could it be that the start temperature is so low the the GC is struggling to cool it and keep it at that temperature? The room is at 29C.

Thanks
~Jo

Almost certainly the room temperature is so high that the GC cannot cool. So the GC not ready messsage is not an error, it is exactly what the control software is supposed to do.

If you look at the GC temperature readout what does it say ?

Peter

In chemstation, in the method edit section for the oven temp program, after it says hold at 245 for 3.5 min on the table, somewhere at the bottom you need to make sure you have put your 35oC in so that it will go back down to it.

I would recommend adding another line in the temperature program that specifies the ramp rate and 35oC endpoint.

Hi this is Kalidass we also observed before the same problem. Ask your instrument engineer to check whether any papers any other particles inside the instrument which reduces the speed of the fan same problem we faced some times.

That is a warm room !

I expect your results are appropriate for the conditions.

When I had to cool down an oven for a low starting temperature I would sometimes put some crushed ice in the oven to assist the process.

How about opening a window or turning the thermostat down to 65 in the room?

Seriously,

Rod

Almost certainly the room temperature is so high that the GC cannot cool. So the GC not ready messsage is not an error, it is exactly what the control software is supposed to do.
If you look at the GC temperature readout what does it say ?
Peter

I think Peter has the reason, tough to cool to 35C with 29C air. Do you have the Agilent accessory deflector (#G1530-80650) and a piece of 4 inch air duct pipe on that unit? We have those on 5890 and 6890, maybe that fits your model too.

Somewhat like trying to cool an old air-cooled VW engine while traveling the freeway in 118F summer heat....

do any of the other methods start at 35oC but still run successfully?

No, we don't have any other methods that start at 35C I think the lowest start temp for other methods is 40 and that one also takes a long time to start. I think we may have found the issue, temperature in the room is too high. Too bad that we can't control the room temperature. We may have to try cooling it by opening the door. Ahh, the joys of doing GC in an Australian summer.

Thanks a lot for all of your help guys, it was very much appreciated.