high cell current

[ratlab]

Hello,

After hours with our HPLC system, in the corresponding manuals and on the internet, I give up. After around 1 month of daily but not intensive use, the pressure and the cell current started to increase and the baseline became noisy.
I first changed the mobile phase for a fresh one. No improvement.
We changed the pre-column, and now the pressure is "normal". (yeah)
I cleaned, then polished the reference and working electrode and coated the reference electrode with its reference electrode solution.
I paid attention to bubbles and not to tight too strong the bolts when I reassembled the flow cell.
I checked bubbles everywhere t is visible on the system.
I performed an electrochemical cleaning of the working electrode by applying pulses of +1 to -1V during 10 min (I know I should have tried this before polishing)
I added more EDTA (it is now 0.1g/L, around 0.2mM) into the mobile phase.
But nothing had neither a positive nor a negative effect.

The screen displays an Icell = +66 nA!!!
(other settings are range NA, Eox=+0.65V, range 20 nA, Offset 0%, Filt. 2s)

The noise of the baseline is of course a problem (I would say it is a regular noise, but the baseline drifts up from time to time) but my concern is more the high cell current. I could not find anything about this issue on the internet whereas I have a list of potential causes of the noise and possible solutions.

Does anyone know? Could anyone explain me a bit about it: what can cause the Icell to increase (decrease?), what can I do to correct it?

Thanks a lot in advance for any information, I feel so alone!

[aceto_81]

Hi,

Do you use post column addition of NaOH?
If so, try to replace your NaOH, this can cause a lot of noise.
Also check if your components of your mobile phase are fresh.
You changed anything? eg switch from reagent supplier, other water source, ...?

Best regards

Ace

[ratlab]

Hi Ace,

Thanks for your answer!
No, I do not use post-column addition of NaOH.
And I also did not change any reagent...
Today we cleaned the mobile-phase uptake frit, the column and the flow cell and I filtered the mobile phase. I cannot say much about the baseline, as I left it was not stabilised, but the cell current was still very high!
I plan to give a try again with polishing again the reference electrode but if it does not work we will try UV detection.
Or do you have other suggestion?

Best,