Baseline jumps

[cody84]

Hi, we are having a problem with our baseline jumping up to around 2000 uV at .75 minutes right where the pressure pulse turns off and the split ratio of 20 turns on. After the jump it is a nice steady baseline. I'm running a Varian 3800. The method has not been changed in years. We have changed septum, liner,columns, cleaned FID, cleaned injector, changed gases and still the baseline jumps for this method. Also created a method where split ratio turns on and off every two minutes that looks good, no basline jump. An injectionless run of the method still produces the jump. Any suggestions?? Thanks in advance!

[haiedc]

Your system may have been backflushed severely. Check and clean further than just the liner , septum. It has nothing to do with the detector.

[cody84]

That makes sense, as we also have some pretty bad tailing/chair shapes. Do you mean clean the gaslines into the injector? If so, do you know how to do that? It's a Varian CP3800 and the injector is a 1177.

Thanks for the reply

[cody84]

I baked the injector overnight at 400 C. Still has the same baseline at 2000ish.
Any help?????

[haiedc]

That makes sense, as we also have some pretty bad tailing/chair shapes. Do you mean clean the gaslines into the injector? If so, do you know how to do that? It's a Varian CP3800 and the injector is a 1177.

Thanks for the reply

I have no experience of Varian GC. You may refer to the manual or ask the vendor for help. Baking overnight almost does no help because the outer parts of the inlet are not any hot at all.

[cody84]

Ok thanks, I have been talking to a Varian tech in the meantime.

[cody84]

After leaving the system conditioning over the whole weekend, the baseline has dropped to around 400. It must be something in the inlet line that's just taking a long time to flush out with some constant flow.