Chromatography Forum

What could cause ECD sensitivity to be lower? Have changed out the column, liners, septa, ferrals, detector liner, and have two new ECD's.

Injector, syringe, autosampler, standard not made up to same strength and your new ECDs are not as good as the old one was.
Sorry not that helpful remote diagnosis is not easy.

aceryy,

ECD is a concentration dependent detector. Therefore, if you have increased the flow within the cell, either with more make-up or with a different column flow you will see a decrease in sensitivity. Also, the detector sensitivity can be temperature dependent for some classes of compounds so that might be an issue as well.

What else has changed?

Best regards,

AICMM

Well all the troubles began when we initially changed the ECD detectors on our instrument. We used two injectors and two detectors, and the ECD signal was starting to get very high so we decided to get new ones. At one point we got it to the point where our front column ECD was OK but not great, but the back column ECD had too low of sensitivity to detect the compounds at the levels we wanted. We then changed all the liners, septa, columns, ferrels, and switched the back ECD to the front and vice versa. After that both had low sensitivity. We may have discovered the problem to be that we used the wrong ferrel on the inlet, but not sure yet if that was what did it. Also the front detector wasn't that snug, so we are going to try tightening that, and making sure the ECD Mug adapter isn't defective. Any other ideas?

After you're sure you're leak free and you have the correct injector ferrule, check your carrier and make up gas flows. As AICMM said, flows (and temp's) effect ECD sensitivity. What instrument do you have?

I checked the flow and it does seem to be low, but it can't be the gas lines because they supply another ECD instrument which is working well. What could be other causes of low flow in a 6890 Agilent? Is there a gas control part that could be replaced?

Tony