Baseline issues

[sagipas]

I am using a 6890 GC with a TCD detector and a N2 carrier gas. Lately I have been having problems with baseline stability, I keep getting square wave
patterns with no apparent periodicity, these can be tens of seconds in duration. The baseline goes up, then stays constant for tens of seconds and then drops back again.

Does this problem seem familiar to anyone? can it have something to do with flow fluctuations?

Thanks a lot!

[Bigbear]

Never run a TCD, but square wave patern makes me think it may be electronic in nature. Any way to monitor detector output with out the column installed?

[AICMM]

sagipas,

You do hear the tick-tick-ticking of the detector all the time, right? Do you have a drop in sensitivity or a shift in retention times?

Best regards,

AICMM