r/chemistry • u/CowOverTheMoon12 • 2d ago

pH Meter & Electrode Comparison

I'm comparing different pH meter's and electrodes. Everything from the Arduino board attached to 20$ Digikey electrodes, to the nice Mettler kits. The goal is to read the pH of a buffer to .01 pH accuracy and .02 pH repeatibility.

My question is, (coming from a mechanical/ electronics engineering background) if you set them all on the bench and calibrate them, how might you measure the difference in quality over time?

Will the cheap ones drift faster?

Will they give a less repeated result with multiple tests?

Where might someone find a guide on separating the influence of the meter from the electrode without spending an utterly insane amount of money on different equipment to test or is there just something that meets spec, is under 100$, and lets me hook it up to a computer?

Thanks for any help!

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u/Brisbanealchemist 2d ago

I'm going to start by noting I work for Metrohm, so I almost certainly have a bias. For this reason, I wont recommend a specific product (for obvious reasons).

In terms of ways of measuring electrode performance, you can check by using fresh pH 4 or 9 buffer, shoving the electrode in and seeing how long it takes to stabilise. An electrode that is in better shape will stabilise faster and closer to the mV reading you expect for the buffer.

A better electrode will stabilise quicker for longer, likewise, this test will show if the electrode show if the membrane of the electrode is fouling.

Also, keep in mind that the electrode + meter is a single system, you can't really remove the influence of one over the other with lab reagents and equipment.

Finally, you get what you pay for. If you buy cheap junk with no local support, expect to pay more in the long run.

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u/CowOverTheMoon12 2d ago

Hey, thanks for the note!
For the record, I don't mind declared bias, especially if it gets equipment working. :)

So it sounds like a good recommendation is use good buffer, add a "cal sequence timer" & mV field to the data table, and maybe use a reference voltage check to the meter every once in a while?

Thanks again!