pH Probe - Issues? Advice? Answers?
Ok, so I am getting my tank back together after a slight hiatus. I had some 7.0 calibration solution in a bottle that hadn't expired so I tested my probe's functionality. 7.1. Great! Didn't have any 4.0 so I ordered some. It arrived today but I am getting ahead of myself.
I tested, just to be sure, the calibration solution with my handy dandy API pH test kit. It read wellllllll below 6.0. That's not good me thinks. Did some reading. Turns out all my test kits were expired. Good thing. I had some old pH test reagent. Ordered some more up. Tested it again when the new stuff arrived, same result. Figured my pH solution was bad since it was opened, albeit capped, but still ruined somehow, perhaps I contaminated it? Who knows.
Well, the new calibration solution arrived today. Tested my probe (which I had left 'calibrated' to the 7.0 from the 'contaminated' calibration solution) and it read 7.0. I was surprised but it read 7.0! Checked the 4.0, it read 3.9 - adjusted the slope.
So, I know that AQUARIUM pH test kits probably only work on aquarium water but does anyone know why? Did some reading on Google but no real clear answer.
Thanks in advance!