Having issues with GC-microECD signal-noise

[andres escobar]

Hi Everyone,

I am having issues wth the signal noise of my GC-microECD. It started to report signals of 4000 to 5000 Hz, and this begun to happen due to the change of the cylinder of the make-up gas (i am using Ar-Me P-5) Before this the microECD reported an aprox. of 300 Hz.
I baked-out the detector at 400°C with constant make-up flow of 60 mL/min, with the oven at 40°C all night, for around 20 hours and the signal was the same as the beginning.
I changed the mixing liner by unscrewing thw swagelok 1/4 and changed the 1/4 ferrule, and installed the make-up gas adapter again by following the instructions in the manual, baked out again and there was no change in the signal-noise.
So, i was thinking in two things.
1. Wait for other cylinder of make-up gas Ar-Me P-5 or...
2. Try to bake-out the detector again but by using HYDROGEN instead of Ar-Me P-5. If this was the case, what conditions do I have to use, i mean, how much time?? constant make-up 60 ml/min of hydrogen?? 40° in the oven??

thanks for your time

[Peter Apps]

Since the problem appeared when you changed gas cylinders, contaminated gas is the most likely source of the high background. Repeatedly baking the detector at its maximum temperature will do no good at all if you are still feeding it with dirty gas.

Don't do anything else until you have clean make-up gas. Expect to have to purge the gas lines for a while before the baseline drops.

Peter

[andres escobar]

Since the problem appeared when you changed gas cylinders, contaminated gas is the most likely source of the high background. Repeatedly baking the detector at its maximum temperature will do no good at all if you are still feeding it with dirty gas.

Don't do anything else until you have clean make-up gas. Expect to have to purge the gas lines for a while before the baseline drops.

Peter

Thanks for your answer.
I changed the gas cylinder just about two hours ago, so i will wait for the signal to decrease.
In case it does not decrease i will ask for the conditions for changing the make up gas.
thanks again