First sincere apologies if this is the wrong community, I don’t have lab science friends to ask about this.
Over the last few months my ph probe has been working well, then over a few days it started to drift down to reporting a ph of 2-3 instead of the 6-7 I would expect. There are so many cleaning procedures out there for ph probes, and knowing how to clean them depends on knowing what is causing them to foul.
I tried using generic probe cleaning solution, 0.1M HCL, and even just a light detergent. Nothing has worked so far.
I was reading that black spots on the ceramic could be from sulfides. And this probe is used 24/7 in my aquarium, where I dechlorinate freshly added water with a dechlorinate that I believe uses sodium thiosulfate. Could that be interacting with the probe’s silver /silver chloride?
I just got thiourea and I’ll be trying to prepare a thiourea/hcl solution.
What else should I try? What else might be causing this kind of fouling/errant results?
That’s a wear part. You can clean it to extend its life, but continuous submersion means these generally need to be replaced regularly. I don’t have one because my tanks are well established and stable, but a friend with a high tech salt setup says she replaces them yearly. Sometimes you get lucky and they just keep working though. Try whatever the manufacturer recommends for general cleaning (best effort here, don’t aim for perfect) and recalibrate it. If it keeps working after that, call it a lucky break and pick up a replacement spare because it will eventually stop working altogether (which may have already happened.)