Chromatography Forum

All, I apologize if there are parts to this question that are missing. I am covering for my superior (who has much more GC/MS experience than me) and we've had an instrument go down completely. There are no peaks on runs (SPME) other than an air peak.

Once I realized this, I checked the tune, and noted that there was almost no abundance showing even with the EM volts maxed out. I attempted to Autotune the instrument, but it stopped during and gave me a "MASG Value out of Range" error.

I checked the Vacuum status of the machine (good), the connections to the source (appear to be good), attempted to ramp the Entrance Lens and Ion Focus (didn't work), and switched filaments based on other suggestions I read. Unfortunately, none of these seemed to help my situation

I believe that I am either experiencing an error with the Electron Multiplier or Quadrapole, but do not have enough hands on experience with the machine to know for sure. I was hoping that someone on this forum might provide insight into what I'm experiencing with this instrument, so that I can start to make moves to either fix the machine, or have someone come out.

Thanks a bunch!

-agwood

If it's an Agilent system, on the top of the page in the tune ap there are a set of MS status that you can check. If they are all ok I would suspect a corrupt tune, it happens quite often with Agilent instruments.
Load the last tune file that ran to completion and use those parameters as a starting point.

Thanks for your help! I re-configured the instrument which reset the Tune file and seemed to have fixed the tune issues. I am currently running a sample to make sure everything runs OK, but it seems to be working OK now (in that I got an acceptable tune).

Thanks again!

-agwood927

All:

So unfortunately, resetting the tune file doesn't seem to have fixed my problem. I'm able to get a tune, but with very very low abundance, and any runs that I do do not produce any chromatography, other than baseline noise.

Does anyone have any idea what could be causing this? I'm thinking there might be multiplier issue, but I'm not sure.

Help?

Thanks again,

What is the vacuum at the source? It should be less than 5x10^-5torr if possible. If it is higher then it has a leak or too high column flow.

With the EM volts maxed out and you still have no signal then it is probably that the EM has gone bad. I have seen them either go slowly where you must increase the volts every day or so until it is maxed out and I have seen them be running perfectly at 1100 volts then give a flat line the very next run.

If possible, please post your tune report.

Hey,

when have you cleaned the ion source the last time?

Is your filament burning? ie, can you see the glow? Are you out of your tuning compound?