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Hi all,
Cheers Darrel
If I was going to get a "cheap" pH meter, I'd get a Hanna one...... Hanna 98129, which is certainly not cheap at $200, but cheaper than what Darrel is suggesting.
That is one of the issues, the electrodes needed to be stored in 3 mol. KCl. The other problem is just that they work via ion exchange and the internal reservoir of potassium ions will eventually be exhausted requiring a new electrode.I believe it has a glass electrode as opposed to ISFET. It has a cap where you can put a few drops of buffer to keep the electrode wet. However, the cap is not airtight, and if you leave it for more than a few days it will definitely dry out. You can get around this by storing the unit upright in a beaker with some buffer at the bottom, sealing the top of the beaker with saran wrap or parafilm, like they do with more expensive probes.
There are ongoing costs involved, with conductivity meters you can make up the calibration solution fairly easily, but it is more problematic for pH buffers.I didn't calibrate mine every time (like you should for proper research). Instead, I would test it against a standard that's close to my target pH. If it was accurate, I didn't recalibrate. Still, this is all added effort, and you do need to periodically buy the standards and cleaning solution. I quite like not having to worry about pH anymore.
You can get citric acid as a dry powder in the UK, not sure about elsewhere.Citric acid would work, but I think strong acids are simpler to use because they don't degrade.
I don't see any advantage to "blackwater extracts" either.The problem with these extracts is that humic and fulvic acids aren't very soluble in water at acidic pH. If they're present in any appreciable concentration, they need to have a strong base added (often NaOH) to remain in solution. The resulting solution will be neutral to alkaline, which isn't the effect you're looking for.
Cheers Darrel