pH calibration / electrode storage solutions

[clowntown]

 

[Haps]

I had the same thoughts when I started hydro, for reference, hydrogenperoxide has a ph of about 4.2. The meters are set up to calibrate to the exact ph's of the cal fluids, can you make something and know it will be stable? It is cheaper and simpler to just buy a small bottle of the two cal fluids.
H

 

[SmokeRings]

Im thinking about doing the same thing, using distilled water (reverse osmosis) and recording how much phUP/DOWN i add to make it exactly 7.0, then using that as calibration solution in the future. Its probably not the most accurate way to do things, but i doubt itll make a big difference

 

[RuralRoute420]

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i bought some bottles, and have never taken any out, i just set my ph pen inside opening in bottle and push calibrate.......is this a bad idea?


seems to be right on everytime, would take a lot of "something" to throw a quart of solution off i would think.

 

[billbob]

RuralRoute420 - that does not seem too safe if you want accuacy. It's not about the 99 times it works, it's the 1 time it doesn't

 

[stevr59]

yeah my hanna says hydrogenperoxide is 4.2 i need some thing thats 7.0 cant aford to buy and calabrating stuff sothis is the only way i can do what i have to do.

 

[clowntown]

So you calibrate at 4.2? Is that technically okay, assuming your device (like mine) allows you to do adjustments at any level? Or seemingly, anyways... I just turn the screw until I dial it into whatever the reference solution says. So with H2O2, I'd simply have to do a 4.2 instead of 4.01, and do another higher, known-pH adjustment for a 2-point?

 

[stevr59]

no not yet i was just checking to see i got the 4.o1 solution but dont have the 7.0 so what i been doing was cal. at 4.0 and then with plain tab water did the 6.8 but not to shure how close i am but it gets me close. but what i need is some thing i can make or some thing arouind the house that would be 7.0

 

[clowntown]

pH up/down, test, sit 24h, re-test, etc, until stable at 7.0? Distilled water of course.

 

[clowntown]

My new Hanna pH pen (HI99104) just arrived today. I noticed that the bottle of distilled water that I have (using for seedlings, etc) reads at exactly 7.00 - 7.01! (My tap reads at ~8.6x!) So couldn't I just use straight distilled water out of the bottle for my 7.01 calibration, and my 4.01 solution (from my previously purchased bottle) for the 4.01 calibration? Or are there extra chemicals or other additives in there that help with calibration or storage?

 

[clowntown]

Ok I'm still not sure why a buffer solution is necessary for storage or calibration (don't know anything about chemistry or whatever), but it sounds like simply calibrating with a known reference of whatever probably isn't a good idea.

Here's what I found:

You can make your own pH calibration/buffer solutions as follows.

* pH 4.00: Add 2.0 mL of 0.1 M HCl to 1000 mL of 0.1 M potassium hydrogen phthalate. (pH 4.00 is used for probe storage)
* pH 7.00: Add 582 mL of 0.1 M NaOH to 1000 mL of 0.1 M potassium dihydrogen phosphate.
* pH 10.00: Add 214 mL of 0.1 M NaOH to 1000 mL of 0.05 M sodium bicarbonate.

For short-term storage (up to 24 hours) place the electrode in pH-4 or pH-7 buffer solution. For long-term storage (more than 24 hours) Store the electrode in a buffer pH-4/KCl storage solution. You can prepare a storage solution by adding 10 g of solid potassium chloride (KCl) to 100 mL of buffer pH-4 solution. By storing the electrode in this solution, the reference portion of the electrode is kept moist. Keeping the reference junction moist adds to electrode life and retains electrode response time when the unit is placed back into use. If the electrode is inadvertently stored dry (NOT RECOMMENDED!), soak the probe in a pH-4 or pH-7 solution for a minimum of eight hours prior to service. The pH Electrode can be cleaned with a light dishwashing detergent solution. For heavy deposits the electrode may be carefully cleaned with a 0.1 molar solution of HCl for no more than 30 seconds, then washed in a light detergent solution. Immediately after cleaning, rinse the electrode in pure distilled water. If the electrode still fails to calibrate properly, or responds slowly, electrode replacement is recommended. Mold growth in the buffer/KCl storage solution can be prevented by adding a commercial growth inhibitor. This mold will not harm the electrode and can easily be removed using a light detergent solution. Do not use the electrode in solutions containing perchlorate, silver, or sulfide ions. Do not use it in hydrofluoric acid or in acid or base solutions with a concentration greater than 1.0 molar. The electrode may be used to measure the pH of sodium hydroxide solutions with a concentration near 1.0 molar, but should not be left in this concentration of sodium hydroxide for periods longer than 5 minutes. Using or storing the electrode at very high temperatures or very low temperatures (near 0°C) can damage it beyond repair.

I guess now I know why my old pH pen went whacko so fast... because I always stored it dry!

But in short, I think I'll just shell out the $13 + tax (plus, I get 10% discount at this one store now!) on the 32oz bottle of storage / reference solution and use it wisely.

 

[Guest]

I spent eighty something dollars on a milwaukee pH51 and it worked great but I also stored it dry,not the best idea.It served its main purpose though which was to check the accuracy and learn the colors of the general hydroponics Ph test kit which is so accurate I dont bother to use my pen anymore.It really is an accurate as hell way to test water/nute PH.

 

[clowntown]

It's also an annoying as hell way to do it too, IMO. After a while you develop a "feel" for how much pH up or down you need to squirt into your mix to get a fairly accurate pH level, but still if you're a little off it's a bit annoying to readjust, pour, rinse out, refill vial, re-test, etc.

Not to mention I hate playing guessing games like: "Hmm, is that a 5.3 or 5.7? Is it more on the yellow-ish or green-ish? Hm, under this light it looks a bit more 5.8, but under that light it looks a bit more like 6.1".

You know what I mean?

That said, I also have a bottle of their green dropper pH test kit just in case I want to "verify" my pen's readings. And that's what I've been using while waiting for my pen to come in the mail (today).

 

[Guest]

I really havent experienced it being a hassle like that man,your getting to worked up over it lol!I can tell a 6.5 from a 6.0 or 7.0,thats as close as I need to be.I usually always use the same ferts so I know how my ferts will interact with the water,I sure dont have to test each time lol.I just check once in awhile to be sure my tapwater ph hasnt changed