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- Posts: 4
- Joined: Fri Feb 16, 2018 5:46 pm
I’m fairly new to ion chromatography and am hoping I can get some troubleshooting advice on an issue I’m having with our Dionex ICS-5000. We test for several anions using an IonPac AS5A-5u column with guard column and use KOH as eluent from eluent generator cartridges. My problem is that I’m getting consistently low values with the first control standard injection for each of 10 analytes being tested for that will gradually increase upon subsequent injections of standard until they get to within limits many injections later. I’m only seeing this on one side of our instrument, the other side with identical hardware and modules does not have this issue.
My initial thought was that there wasn’t enough sample being injected on to the column due to some kind of blockage in the line. The back pressure wasn’t abnormally high but I changed the sample transfer line and tubing up to the suppressor/detector anyways. Immediately after this the control values were consistently 2-3 ppm above the expected and just above our accepted range. I figured a recalibration was necessary and the first control values immediately after calibration were all within 1 ppm of target, but the next few dropped by a couple ppm and are now all just outside of accepted range. After turning off the pump, EG, etc. and going through standard pump and column conditioning the next day I’m now seeing control values 10 ppm lower than target.
With my limited experience I am unsure of what the issue might be. If anyone has suggestions or advice that would be greatly appreciated. Not sure if I gave enough info on hardware components or run method, I can provide more info if needed.
Thanks in advance,
John