pH Probe Storage

[Spartan1979]

I got a pH meter for Christmas. I got a handheld model with a separate probe. It's my third meter as the first two were ruined when the probe dried out as I wasn't brewing often enough.

Anyhow, I was thinking of storing the probe in a small flask and fitting a drilled stopper around the probe. Any reason this wouldn't work?

Thanks.

 

[ajdelange]

Check the instructions that came with the meter. The electrode was doubtless protected with a cap of some sort when it arrived. The cap probably has a small sponge in it. A few drops of probe storage solution (which is available from the manufacturer) on that sponge renewed periodically is enough to keep the probe hydrated and functioning for a long time.

 

[mabrungard]

A White Labs yeast vial with a hole drilled in the cap to fit the probe works very well. Fill the vial with storage solution and insert the probe through the cap. I made a wire loop to hold the vial and then I hung the assembly on my workshop pegboard.

Easy and cheap...good characteristics for most projects.

 

[Spartan1979]

This is what I ended up with:

 

[ajdelange]

That is a very appealing method of storage and fine if the manufacturer approves it. With some electrode designs you will come back to find all the electrode's gel transferred to the storage solution in the bottle. That happened to me with one electrode for which I 'improved' on the manufacturer's small storage cap and sponge (it kept tipping over and spilling) by using a small polyethylene bottle with a hole in the lid which I had saved from a discarded electrode that used that method of storage.

The message is that it is always best to do what the maker of the electrode recommends. If the manufacturer's instructions say nothing about storage then get another meter/electrode .

 

[terrapinj]

I just got a Hannah meter for christmas and it didn't have a sponge in the cap but says to store with water and a few drops of storage solution, but very specifically says not to use Distilled or RO water - i figured Distilled water would be ideal

any idea why they advise to not use distilled/RO?

 

[ajdelange]

I'm not privy to the design of this electrode (and even if I were I probably wouldn't understand it) but I can make a general comment or 2. Material moves along gradients of chemical potential (much as anything with mass moves along gradients of gravitational potential) if they can. Distilled water is devoid of ions (with the exception of H+ and OH-) and molecules (with the exception of H2O). Therefore there would large chemical potential differences between the DI water and 1) the chemicals on the other side of the reference junction and 2) the interior of the hydrated (leached) layer in the sensing bulb glass. This would cause, for example, potassium chloride in the electrode fill gel to want to migrate to the distilled water if indeed the gel contains potassium chloride which is a good guess but not necessarily true of this electrode. The proper storage solution in this case would contain KCl so that the potential across the junction is small or 0 and the KCl stays where it is supposed to be. Similarly, the functioning of the meter depends on certain ions being "dissolved" in the bulb glass and the recommendation may have something to do with that but I'm guessing it's the junction they are concerned about.

 

[terrapinj]

thanks for the reply, that makes sense to me, I had just assumed pure water = better water

 

[mdanilow]

I work in a biotech company where we use pH probes. We store them in a KCl solution like ajdelange suggested in a previous post. This is per the manufacturer's recommendation. i am not sure what type of paperwork you got with the probe, but it should be in there or you could contact the manufacturer and see what their suggestion is. We also frequently change out the solution, but that is probably not very necessary in a home setting, just pay attention to the expiration date of the solution.

 

[day_trippr]

I just read the instructions for the Hanna 98128 and what it actually says is to rinse the electrode probe with water, then store it with a few drops of the HI 70300 storage solution in the protective cup/cover. I don't think you're supposed to put any water in the cup during storage.

Another part of the instructions says if the electrode "has been left dry", to soak in the storage solution for at least one hour to reactivate it.

My (new) 98128 arrived dry, so I'm presuming I'll need to do this soak before first use. But this leaves me wondering if one could simply rinse then leave the electrode to dry between uses, then go through the soak when needed, without causing any negative effects...

Cheers!

 

[ajdelange]

You will definitely have to hydrate the glass at first use and rehydrate it subsequently if it is ever allowed to dry. I cannot believe that repeated cycles of drying and rehydration would be good for the bulb but my main reason for thinking that is that the instructions suggest that it be kept hydrated. I'd guess the response time would slow sooner than it would, i.e. that the electrode would age faster, than it would if stored as recommended.

 

[day_trippr]

You will definitely have to hydrate the glass at first use and rehydrate it subsequently if it is ever allowed to dry. I cannot believe that repeated cycles of drying and rehydration would be good for the bulb but my main reason for thinking that is that the instructions suggest that it be kept hydrated. I'd guess the response time would slow sooner than it would, i.e. that the electrode would age faster, than it would if stored as recommended.

Yeah, I'm pretty much in agreement with all that. Just wish they were a bit more informative in their rather terse instruction "manual" about such things, considering how pricey a replacement electrode is.

Said instructions say to just put a few drops of the storage solution in the cap between use, but that vague description leaves me wondering if the intent isn't to actually leave the electrode in "full soak" during storage, but to provide some level of humidity in the micro environment around the bulb.

Given earlier comments about leaching electrode gel, I would appreciate your advise on that detail...

Cheers - and thanks for your help!

 

[ajdelange]

I rather suspect the object is, as you have guessed, to keep it humid. That will prevent the bulb from drying out and also keep moisture from passing through the junction. If you fill the cap with liquid you will experience potassium chloride "creep" assuming that the storage fluid is a solution of KCl which it usually is. Even though the cap is tightly sealed you will find crystals of KCl on the outside.

 

[BWN]

In the lab I work in we store our probes in 4.0 buffer solution but they are frequently used. For long term storage we keep them in a KCL solution. In the picture at the beginning of the thread it looks like the probe is in 7.0 solution(I could be wrong) which is usually not recommended, but you should go by the manufacturers instructions.

 

[day_trippr]

Interestingly, the MSDS for the Hanna HI 70300 storage solution states the pH range is 5-7...

Cheers!

 

[ajdelange]

DI water also has a pH between 5 and 7 as do lots of other things but BWN's point is that it appears from the photo that the probe is being stored in 7 buffer which is not a good idea unless the manufacturer specifically recommends it.

 

[Spartan1979]

DI water also has a pH between 5 and 7 as do lots of other things but BWN's point is that it appears from the photo that the probe is being stored in 7 buffer which is not a good idea unless the manufacturer specifically recommends it.

It's not 7 buffer, it's storage solution.

Genesis Electrode Storage Solution - 16 Ounce