Chromatography Forum

I just did some general maintenance on our dual GC/ECD and I am having some retention time shift forward on one detector and backwards on the other. The one with the backwards shift is also getting very low response from standards (but curves are linear). Any idea what could be the problem? Just installed a new splitter from a single injection port.
Any input is welcome, let me know if more info is needed.
Thanks!

I just did some general maintenance on our dual GC/ECD and I am having some retention time shift forward on one detector and backwards on the other. The one with the backwards shift is also getting very low response from standards (but curves are linear). Any idea what could be the problem? Just installed a new splitter from a single injection port.
Any input is welcome, let me know if more info is needed.
Thanks!

Can you leak check the splitter? My instinct would be to try redoing the maintenance that you did.

For diagnostics you could try switching which column goes to which detector to see if the low response stays on the same detector (demonstrating a problem with the column) but that is probably over-complicating things.

I leak checked the splitter connections on installation, it's all good. Is it possible that there is a difference in gas-flow to each of the detectors, i.e. the spiltter could be 'clogged' on one end?

If there is a small clog or restriction in one column then the flow would be slower and elution times later, while the extra flow would go to the non-restricted column causing faster elution times. Could be as simple as a piece of graphite from the ferrule stuck inside one column. I would try trimming both columns a few inches and see if that fixes it.

Ok great, thank you for your suggestion... I was thinking it might be something like that.