PH Meter, DM H2o, DeIonized H2o

[Bubbles2]

So I got a new PH meter, came with the powder packs with instructions to hydrate using DEIONIZED h20 not Distilled, see difference when calibrating a sensitive piece of equipment.

Here is the thing with the buffer solutions I am confused a bit about.

The Deionized h20 is recommended to be stored in Stainless and to avoid Co2 and begins to degrade almost immediate once exposed to air/elements. yet Sold in Plastic PET, which is Okay.
Ok to store in PET plastic but once opened it starts to degrade as it is exposed. And will settle out at 5.5- if mixed as a 4,7, or 10 buffer...(over time)

Anyone out there using lab equipment and have thoughts on just buying the packets and mix as needed with deionized water?
My thoughts are that the DM h2o gets contaminated once opened and if sitting will fight to get it's minerals....Then using later with a fresh packet the water is now contaminated (for a lack of better term)
OR do you buy 125ml's pre - mades and replace once they begin to read wrong at the 5.5 they seem to settle out at after time, but is that calibration issue and when do you know the difference?

 

[Robert65]

I buy the single use sachets of pre mixed calibration solutions and discard after use. Safest bet for reliability. As you note, a single use will contaminate the solution so that accurate calibration will no longer be possible, and once mixed or opened the shelf life is limited anyway, leading to the same result. Cleaning and storage solutions can be brought in bulk, cleaning is just hydrochloric acid really, and storage a saturated (4M) KCl solution. Thse will not deteriorate but must never be returned to the bottle after use. RO water is good for rinsing between calibration points and before and after testing a sample. This practice has served well for many years.

 

[Bubbles2]

I buy the single use sachets of pre mixed calibration solutions and discard after use. Safest bet for reliability. As you note, a single use will contaminate the solution so that accurate calibration will no longer be possible, and once mixed or opened the shelf life is limited anyway, leading to the same result. Cleaning and storage solutions can be brought in bulk, cleaning is just hydrochloric acid really, and storage a saturated (4M) KCl solution. Thse will not deteriorate but must never be returned to the bottle after use. RO water is good for rinsing between calibration points and before and after testing a sample. This practice has served well for many years.

I forgot about the pre made sachets... Thanks Big sites like Eba or AmaZ where you get yours? Spendy little suckers

 

[Robert65]

I forgot about the pre made sachets... Thanks Big sites like Eba or AmaZ where you get yours? Spendy little suckers

My meter was made by Hanna, so I buy solutions direct from their website. You could try other manufacturers' sites too. Bulk buying more than offsets shipping for me. All I can say is shop around. Anything is cheaper than buying them individually from my local shop. Haven't recently checked if I could do just as well paying a middleman's markup but with free Prime shipping. Anyway I'll pay a bit to know I'm getting it right every time.

 

[Bubbles2]

Are you just buying the two 4 & 7, since you are using it for brewing or wine? I have a 3 point which uses a 9.9 or 10.1 whatever it is

 

[Robert65]

Are you just buying the two 4 & 7, since you are using it for brewing or wine? I have a 3 point which uses a 9.9 or 10.1 whatever it is

Yes, just 4.1 and 7.1. You don't need 3 point calibration for a limited range use like beer or wine, you just want the two points that bracket the range you'll be working in. Your meter never needs to know what 10.0 tastes like.

 

[RPh_Guy]

Like @Robert65 I use an old model Hanna meter. I get liquid calibration and storage solution from my usual supplier, MoreBeer.
As mentioned, don't put used solution back in the bottle.

I use it frequently enough (calibrating before every use), that shelf life isn't really a problem, and for what it's worth I store solutions in the fridge.

I use test tubes for calibration and filtered water for rinsing.

OR do you buy 125ml's pre - mades and replace once they begin to read wrong at the 5.5 they seem to settle out at after time, but is that calibration issue and when do you know the difference?

You aren't understanding correctly.
The solutions are assumed to be correct and then you adjust the meter (which is assumed to be incorrect) to match the calibration solutions.
The meter will drift much more rapidly than the calibration solutions.

 

[Bubbles2]

Like @Robert65 I use an old model Hanna meter. I get liquid calibration and storage solution from my usual supplier, MoreBeer.
As mentioned, don't put used solution back in the bottle.

I use it frequently enough (calibrating before every use), that shelf life isn't really a problem, and for what it's worth I store solutions in the fridge.

I use test tubes for calibration and filtered water for rinsing.


You aren't understanding correctly.
The solutions are assumed to be correct and then you adjust the meter (which is assumed to be incorrect) to match the calibration solutions.
The meter will drift much more rapidly than the calibration solutions.

I understand (so I think with my perceived knowledge)
The Solutions once contaminated with Co2 which turns into carbonic acid.
Cite- (see DI water storage for ref)
http://www.tmasc.com/di water specs.htm

 

[RPh_Guy]

Some dissolved CO2 can easily shift the pH of DI water which has literally nothing to buffer it, but it's not going to hugely shift the pH of the calibration solution, which has lots and lots of buffering.

 

[Bubbles2]

Some dissolved CO2 can easily shift the pH of DI water which has literally nothing to buffer it, but it's not going to hugely shift the pH of the calibration solution, which has lots and lots of buffering.

That is good to know, especially when wanting to buy solution as stated above