GC Closing CC Problem
Posted: Tue Sep 25, 2018 9:15 pm
So I have these two GC instruments with ECD detectors, HP 5890 and Agilent 6890, that I use for pesticide testing. They're great instruments, however the 6890 is giving me an issue. Whenever I run a batch of samples and there is something over my calibrated range, my closing CC tends to fail low for DDT and methoxychlor. ALL of the other compounds read right at what they should. Now, its not that big a deal cause I can fix this by changing the liner and everything goes back to normal.
However, on the HP 5890 I can (and have, for testing) run the same samples, and even with some samples over range the closing CC will pass for everything. I can't seem to find a reason why that is. They both use hydrogen as the carrier gas, use the same liners, and even the same column I think. I would have thought the 6890 would be performing better than the 5890, but that doesn't seem to be the case here. I recently did full maintenance on the 6890, and its still the same, so not sure what it could be. Any insight would be helpful.
However, on the HP 5890 I can (and have, for testing) run the same samples, and even with some samples over range the closing CC will pass for everything. I can't seem to find a reason why that is. They both use hydrogen as the carrier gas, use the same liners, and even the same column I think. I would have thought the 6890 would be performing better than the 5890, but that doesn't seem to be the case here. I recently did full maintenance on the 6890, and its still the same, so not sure what it could be. Any insight would be helpful.