Question about PH Meter Storage Solution

pH buffer should be safe enough for the time being, but 4N KCl solution is what's recommended for storage. That's pretty close to saturated IIRC.

BTW, I've noticed that something tends to grow in the storage solution, so I boil it and immerse the electrode while the solution is still hot when I put it away for the time being.

Tom S

. The most critical part of the electrode is the tip at the bottom. This round part is actually a membrane that has small pores. If these pores become plugged, the electrode will not work or will work poorly (slowly or irreproducibly). Never wipe the bottom of the electrode with a cloth or anything. Don't touch it with your fingers. Clean it by by rinsing or soaking it. A small squirt bottle is handy for rinsing. [Please note: The instructions that come with the meter instrucy you to dry the tip with a soft tissue during calibration. There is no need to do this and you risk damaging the tip.]

1. What can plug the pores? Must or wine or wort or beer can all plug the pores so it is a good idea to rinse your electrode after each use. Colored buffer solutions may also plug the pores if the electrode is stored in them. [The buffer capsules make uncolored buffers.]
2. You can tell if the pores are plugged if your meter operates slowly and/or the reading is inconsistent.
3. If the electrode is left out and the tip is not kept wet, then you may need to soak the electrode for several hours in storage solution (best) or buffer solution. The soaking simply opens up the pores. You should not soak or store the electrode in distilled water. If you have nothing else, tap water is okay and much better than distilled water.
4. The German pH meter is not a sealed (gel filled) electrode such as that on the Checker [Gel filled electrodes are good for pocket meters where durability is an issue but are otherwise inferior to a refillable electrode.] The electrode must be filled with reference solution (KCL) occasionally. [It is a double junction electrode which means you do not need AgCl/KCl as in a single junction electrode.] The formation of salt KCl crystals is normal and not a concern. However, the hole should not be plugged during use. When it becomes plugged, simply wipe off the crystals or use a toothpick to open the hole.
5. The electrode need not be full to operate properly, but the lower part where the pores are, must be full. Generally, I only refill if it gets more than half empty.
6. Store the electrode in the Storage solution. The electrode comes with a plastic cover for the tip. Simply put a little storage solution in the cover, insert the electrode, and it will keep well.

Paul,

The instructions I got with my Hanna pHEP unit is to store it in storage solution or pH 7.01 calibration solution. The cap is designed to hold several drops for this purpose.

Cheers,

Glen Duff

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Paul S. Rem> Hey there everyone!

Same stuff as within the electrode for me: 3M KCl (Metrohm probe). Everything else will make the probe 'leaking' salts, therefore, do (preferably) not use the pH7 buffer, and certainly not distilled water. Watch out for growths as Tom already mentioned, fungi other than Saccharomyces are everywhere although this high conc of salt generally will not grow much.

Rene.

The reason I recommended heating the KCl solution is that there _was_ something growing in mine.

BTW, to rejuvenate pH probes, someone here recommended contact lens enzyme cleaner. Sounds reasonable to me, but I haven't tried it yet. Worth a try if the probe is otherwise junk, I'd say.

Tom S

Storage solution is in principle similar to the electrolyt within the probe, maybe with some preservative added for the problem Tom mentioned.

For me, that is 3M KCl (or 224 g/l if I remember correctly) for a Metrohm probe. All other solutions will leak salts from the probe, but that's preferable to dry storage!

Rene.

I was wondering about using contact lens saline. I'm currently using tap water run through a new PUR water filter.

One other question... I noticed my probe takes about 30 minutes to provide a stable reading. My first reading with the probe showed the must to be about 3.4 after three minutes or so. I left the probe in the must for a good half hour and the reading VERY slowly dropped to

Is this normal??? Is the 3.15 reading reliable? I didn't know it takes so long to register a reading using a PH meter.

-Paul

Not trying to get my point through :), just not sure google groups did go right first time.

Anyway, Tom's rec about probe cleaning is right, often a procedure with pepsin in 0.1M HCl is mentioned in instruction manuals. Clogging happens easily in the food industry, not really when working with wines. Beer musts?

Rene.

Actually, you mean beer worts. Wort/must doesn't become beer/wine until the yeast is pitched. In beermaking, there's no concern about the pH of the wort, but some guys do check the pH of the mash (the "porridge" step where water and grains are mixed). IIRC, the right pH helps the conversion of starch to sugars, but most homebrewers don't worry about it. Ken A.

Your readings are taking so long because you've been incorrectly storing your pH probe. Water will leach the KCl from the electrode. Contact lens solution is not made for that application either. Store it in boiled, saturated KCl solution.

Tom S

What's interesting is, it took that long before I ever had a chance to store it! I first used it the other day. I placed it on 4.0 PH buffer solution and it took a good 15-20 minutes to settle, then I calibrated it. Did the same for the 7.0 buffer. Then I did tests with my must during the course of the evening, rinsing and placing the probe back in the buffer solution in-between tests.

All tests took about 20-30 minutes before the meter provided a steady reading. Do I have a "sick" electrode?

-Paul

I'm using the exact same meter... although I don't see that in my instructions. I've been using the pH buffer solution to store it. Glad to know that's safe until I can get my hands on KCl solution. Thanks!

One of my friends works in a food testing plant and they have gallons of buffer solutions (clear). He's gonna draw-off a bunch for me. I'll have to ask if they have KCl.

-Paul