Chromatography Forum

hi all,

After I changed the He gas cylinder, the gcms can not run sample now. All the parameters are fine. After I click 'OK and run', there is a small window saying: GC verifing, waiting for GC ready". However, after 1 hour, the small window is still there and sample still cannot be injected. I tried to restart the software, the computer and create a new method, the problem is still there. So what I can do now? Thanks a lot

Press the "Status" button, see what it states. If that's correctable, do that.

If not, press the "Pre-Run" button, and/or click to overide the not-ready condition.

If your GCMS is not Agilent: Never Mind !!!

What make and model instrument do you have? This would help. If the inlet shows the proper pressure, the problem is either not related to the gas cylinder change or is indrectly related to it. Be sure the pressure beign delivered to the instrument from the gas cylinder is set correctly (too low from the bottle, and you will never get the right pressure at the instrument) and that the cutoff valve from the regulator into the gas line (if you have one) is open. I would suggest checking to see if the gas cylinder valve is open,but then I might have to admit how I would think of these things...

Good point, Don. I never did that...not! Just want to add, make sure it's completely open. If partially open it could cause problems, too.

My GCMS is Agilent 7890/5975. The out pressure of cylinder is about 75 psi and the inlet pressure is the same with the setpoint. The inlet temperature is 250 and the gas flow in the column is 1.1. I also decrease the equilibration time to 0.5min. I have no idea what else need to be checked.

Try shutting down the PC (shutdown, not restart). When the PC is down, power off the GC. When the GC is off, power off the MS for 5 seconds and turn it on. Wait a minute or so and power on the GC. Wait until the GC is back and then reboot the PC. Once it's back, try loading your method and hopefully you're OK. Good luck and please keep us informed

Set the outlet pressure from the gas cylinder to at least 20 lb above the highst pressure the inlet will demand. There is pressure regulation in the GC and if it is trying to deliver the same pressure to the inlet that it is receiving at the back of the instrument, it will have a very hard time providing a stable pressure... Also note the maximum pressure your instrument will handle from the bottle. Go over that and you risk damaging the instrument.

Thank you all for your reply. The problem has been solved. For this Agilent 7890 GC, we installed two ALS and two columns. We seldom use the back one. So after changing the cylinder, I did not turn on the back inlet pressure, only turn on the front one, So I think that is why the GC waiting for ready.

There should be a setting within Chemstation (in Chemstation E.02.01, in the GC Edit Parameters screen, it's the "Readiness" tab) that will allow you to select which zones affect the GC becoming ready. You can de-select the back inlet for the methods in which you do not use it, thereby avoiding this problem in the future.

There should be a setting within Chemstation (in Chemstation E.02.01, in the GC Edit Parameters screen, it's the "Readiness" tab) that will allow you to select which zones affect the GC becoming ready. You can de-select the back inlet for the methods in which you do not use it, thereby avoiding this problem in the future.

Thank you for your suggestion! Do you mean that if I uncheck all in the "Readiness" tab, the GC will never get ready? However, the weird thing is that there is no "readness" tab in this GCMS, is that because the version of the software?

If you uncheck the box, the GC will not wait for that zone to become ready. Therefore, in your case the GC would not have cared about the back inlet pressure because you would have unchecked that box as being necessary for the entire system to be considered "ready". If you don't have the E.02 Chemstation, then I don't think you have that option.