I am running a GC with ECD Detector. I have been running it for over a year without any unusual problems, other than the mV level slowly increasing over time.

About 3 weeks ago ECD mV level was at its saturation point of over 800 mV.
I performed an ECD bake out and the mV level dropped below 100 and stabilized at about 70 mV.

Last week I noticed the mV level starting to rise and fall daily from 70 to 90 mV back to 70.

This weekend I ran a series of isooctane blanks.

This morning my ECD level was back above 800 mV.

Is there anything that could be causing this? I would like to investigate every possibility before I consider having the detector refoiled.

Thanks in Advance.