PH powder solution question

[Droopydroors]

I hope I'm putting this in the right place but I'm sorry if not. I can't seem to find the answer to this question so I figured others might benefit. I got a cheap digital ph meter and it can with 3 packets of powder solution to mix with distilled water for calibration. I was just about to order more because I thought they were "one time" use. Can I mix these solutions and put them into air tight containers and use them for a period of time? If so how long is that time.

 

[The Germinator]

I bottle mine up and reuse. I don't know how long they are good for though. Just started doing this and haven't decided. I'll mix up a fresh batch soon and test against what I've saved. Good luck to you.

 

[Droopydroors]

Thank you! Ya I was about to order 15 packs because I use it often and figured that it's so cheap that it will probably get off rather quickly. This way since I have them in bottles I can test it before every use and calibrate it when needed.

 

[dj1714]

I bottle mine up and reuse. I don't know how long they are good for though. Just started doing this and haven't decided. I'll mix up a fresh batch soon and test against what I've saved. Good luck to you.

What a great idea. Can you post back and let us know the comparison.

 

[The Germinator]

Will do. Ordered a new meter. Will test the old and a new batch.

 

[Scientific]

It's much better to buy bottled calibration solutions (for example General Hydroponics pH 7.0 standard) than to mix from Kool Aid packets. You can get bottled pH calibration solution at the hydro shop or at Amazon.

Calibration standards really should be made with water measured using laboratory grade water measuring equipment (a calibrated flask) to be accurate. Mixing a calibration standard using your wife's measuring cup is kinda like the old joke about measuring with a micrometer and then marking with chalk.

A cheap pH meter can give perfectly adequate results, but any pH meter (even a $2000 one) is only as good as its calibration, and hence its calibration solution.

(And to answer your question, yes, you can keep pH buffers (i.e. cal solutions) just about indefinitely as long as they are kept tightly sealed.)

 

[Droopydroors]

Thank you! The problem is the pH meter I have is a digital one that needs the 6.86 and 4.01 to calibrate it. I haven't seen any solutions in those levels.

 

[Dwight Monk]

Thank you! The problem is the pH meter I have is a digital one that needs the 6.86 and 4.01 to calibrate it. I haven't seen any solutions in those levels.

IMHO that is just a "ploy" to get you to buy their solution(s), just need a high and a low as you can get it calibrated to one and it can be off on the other, so many are 4.0 and 7.0, and you can't convince me a solution of 4.01 is going to be any different than a 4.0 to calibrate with . They do have a shelf life once opened and once you use it (put electrode into it) then it is contaminated and no longer totally accurate, so don't put probe directly into your bottle pour what you need to check it and toss it when done. Most have a expiration date on the bottle and according to a companies site I looked it said this:

Our calibration solutions are designed to have a long shelf life when left unopened. Once opened, a buffer with a pH lower than 7 will last around 3-6 months, while a buffer with a pH over 7 will be good for about 1-3 months

Factory I worked at calibrated them every day, but because the City would fine them big time (thousands of dollars per infraction) if the Effluent water we sent back to the City wasn't in a certain PH range (had to be between a 6.1-8.9). As we would alter the PH on the pulp with chemicals (so bring it up to a 12.0 and then back down to a 4.4), as a higher PH the recycled material would break down faster/better and a lower one the fibers will stick/inter mingle with each other better. Pretty sure they used a 4.0 and a 7.0 for calibration solution, and we used the $3-400 expensive handheld meters (they would have a cow when you broke/damaged one ).

 

[Scientific]

you can't convince me a solution of 4.01 is going to be any different than a 4.0 to calibrate with

Absolutely. For the technically minded, the pH 7 calibration solution is used to set the 0 point of the amplifier in the meter, the pH 4 solution is used to set the amplifier gain. (Here's a link to a page about building and adjusting a simple pH meter that's kind of interesting.)

All that matters is that you calibrate the meter to known values (e.g. pH 7 and 4). The exact value you calibrate with isn't important as long as it's accurate. (And truth be told, I only calibrate my pH pen with pH 7 solution. That's close enough for pot farming.)

 

[Droopydroors]

The cheap meter I have does not let you pick what to set the meter to? You have to click the button for 5sec and release then 6.86 appears to get the second point you click for 5 seconds, release, click one more time and it goes to 4.01 so there is no way to trick the meter into reading a 7 because if you do that everything would be off.

 

[Scientific]

The cheap meter I have does not let you pick what to set the meter to? You have to click the button for 5sec and release then 6.86 appears to get the second point you click for 5 seconds, release, click one more time and it goes to 4.01 so there is no way to trick the meter into reading a 7 because if you do that everything would be off.

That's a terrible design! I hate to say it, but I think you need to buy a new pH pen. They don't cost very much...

 

[The Germinator]

What a great idea. Can you post back and let us know the comparison.

Been using new calibration solution and a container of used solution to test calibration. First I use the brand new stuff. Bam 7.0 then I dip into the used stuff. Bam 7.0 I've done this everyday now for 9 days.
So my conclusion is that it's crazy to throw away your used solution after each use. I keep my used in an old 35mm black plastic film canister. The website for my instrument says throw away after ten uses. Here's a cut and paste.
For pH calibration buffer solutions, we recommend that users pour the solution in an additional cup or calibration cup if given (and keep the cup closed when not in use). You should replace it with new pH buffer solution in the bottle after approximately 10 times of use.

For Conductivity buffer solution, we recommend about 5 times of use before replacing new calibration solution.

Do not put used buffer back in the original bottles. There could be some substances that the sensor acquired to contaminate the solution, therefore if you put it back in, It could ruin the whole solution. And always keep the original calibration solution bottles tightly closed and stored in room temperature.

 

[Scientific]

Been using new calibration solution and a container of used solution to test calibration. First I use the brand new stuff. Bam 7.0 then I dip into the used stuff. Bam 7.0 I've done this everyday now for 9 days.
So my conclusion is that it's crazy to throw away your used solution after each use. I keep my used in an old 35mm black plastic film canister. The website for my instrument says throw away after ten uses. Here's a cut and paste.
For pH calibration buffer solutions, we recommend that users pour the solution in an additional cup or calibration cup if given (and keep the cup closed when not in use). You should replace it with new pH buffer solution in the bottle after approximately 10 times of use.

For Conductivity buffer solution, we recommend about 5 times of use before replacing new calibration solution.

Do not put used buffer back in the original bottles. There could be some substances that the sensor acquired to contaminate the solution, therefore if you put it back in, It could ruin the whole solution. And always keep the original calibration solution bottles tightly closed and stored in room temperature.

I reuse my calibration buffer too. As long as you're not carrying over a lot of water from the rinse and you cover the container so it doesn't evaporate, why not? It's just a salt solution. Yeah, in the lab where we had unlimited budget and were doing serious chemistry we'd never do that, but for home use? It's fine.

I miss 35 mm film containers! I'll bet there are people reading this already who have no idea what you're talking about.

 

[The Germinator]

 

[dj1714]

First I use the brand new stuff. Bam 7.0 then I dip into the used stuff. Bam 7.0 I've done this everyday now for 9 days.
.

That's great news Germinatorn, +reps for testing this and letting us know. You always seem to learn something new everyday.

 

[dj1714]

I miss 35 mm film containers! I'll bet there are people reading this already who have no idea what you're talking about.

I just got rid of a couple of a couple packs of polaroid film that I didn't know that I had stored. LOL