Storage solution for SensorDisc electrode

There are a few versions I know of
a 3M KCl

b ph 4 buffer solution with a slug of saturated KCl

and I now see
c equal parts 4M KCl and pH 4 buffer

As far as I know, the commercial solutions have antibacterial agents so they last longer without algal growth, but the KCl solutions work fine, you just have to check them occasionally and pipette out the the growth (If you are feeling lazy) or replace the solution.
 
There are a few versions I know of
a 3M KCl

b ph 4 buffer solution with a slug of saturated KCl

and I now see
c equal parts 4M KCl and pH 4 buffer

As far as I know, the commercial solutions have antibacterial agents so they last longer without algal growth, but the KCl solutions work fine, you just have to check them occasionally and pipette out the the growth (If you are feeling lazy) or replace the solution.

So, I have to prepare a ph 4 buffer solution, a 3M KCl solution, and mix them in equal parts. Is that correct?
 
From Hanna Instruments website: https://www.hannainstruments.co.uk/home/2284-hi-70300s-electrode-storage-solution-30ml

They suggest that pH 4.01 or 7.01 buffers can be used if storage solution is running low..... but I guess these won't have mould/bacterial inhibitors so would need changing more often....

I've used 15% KCl in the past (before we started buying the storage solution in for convenience) with no loss of functionality (with Hanna pH checkers that is - not sure about your sensordisc one...!)

1655801124076.png
 

From Hanna Instruments website: https://www.hannainstruments.co.uk/home/2284-hi-70300s-electrode-storage-solution-30ml

They suggest that pH 4.01 or 7.01 buffers can be used if storage solution is running low..... but I guess these won't have mould/bacterial inhibitors so would need changing more often....

I've used 15% KCl in the past (before we started buying the storage solution in for convenience) with no loss of functionality (with Hanna pH checkers that is - not sure about your sensordisc one...!)

View attachment 9252
Did you just prepare a 15% KCl solution and immersed the electrode into it? Unfortunately, we don't have the chemicals needed to prepare the pH 4 and pH 7 buffers nor buffer tablets, so there aren't many options left...
 
Did you just prepare a 15% KCl solution and immersed the electrode into it? Unfortunately, we don't have the chemicals needed to prepare the pH 4 and pH 7 buffers nor buffer tablets, so there aren't many options left...

Basically, yes - the Hanna checkers we have come with a little rubber/plastic cap that sits over the bulb of the pH meter - provided the solution covers the tip (bulb) and the junction where it joins the rest (the body) of the probe/meter it should be fine.... Does your probe have a cap to put over the end? If not, you could fashion one out of a bit of tubing or a pen cap or something similar and tape it on.....

The intention is to stop the bulb part and the junction from drying out (which can permanently ruin the probe); a concentrated salt solution is used to stop the stuff inside the bulb/tip from leaching out (if it was stored in distilled water the contents would leach out into the water over time, also permanently ruining the probe....!)
 
Basically, yes - the Hanna checkers we have come with a little rubber/plastic cap that sits over the bulb of the pH meter - provided the solution covers the tip (bulb) and the junction where it joins the rest (the body) of the probe/meter it should be fine.... Does your probe have a cap to put over the end? If not, you could fashion one out of a bit of tubing or a pen cap or something similar and tape it on.....

The intention is to stop the bulb part and the junction from drying out (which can permanently ruin the probe); a concentrated salt solution is used to stop the stuff inside the bulb/tip from leaching out (if it was stored in distilled water the contents would leach out into the water over time, also permanently ruining the probe....!)
Our electrode is inside a small plastic bottle with a screw cap that contains the storage solution. The bottle is half full now, and it seems that the tip (bulb) of the electrode is still covered by the solution (please, see pictures below). I am not sure if I have to fill the bottle completely or just wait until the amount of solution is very low. Then, I will replace it with 15% KCl assuming that by then we can't buy the storage solution recommended by the supplier (Findel).
 

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STEMTech

Dave
CLEAPSS have a guide on storage of sensor probes with details on how to make your own solutions. It's document TT008.
 
We keep ours (both cabled probes and checker sticks) in small conical flasks with bungs with holes in, so the flask contains enough storage solution to cover the bulb and more. That means even if some does crystalise it takes a long time to dry out enough to put the bulb at risk.
I have some spares in these 'caps' and small bottles but the problem I have with them is 1) the amount of solution is small, so once it starts to dry out there isn't much leeway
and 2) using them (the more cap-like ones) means the solution probably ends up spilled, so you have to refill them. Or best stored upright or they risk leaking.
The flasks remove those issues, although they do take up more space, of course. But they live in the lab and need no tech input apart from visually checking there is enough solution and it is not starting to grow fuzz!
Having read (and been taught in industry) all the warnings about drying them out, I recently found a tray with several old probes, all dried out for at least two or three years, probably many more (past tech turnover - at some point they were rejected as not working and 'stored', but dry) - a bit of cleaning and soaking cycles, and almost all of them are reading fine! They are hardier than I thought!
These were probes, not the checker sticks, although they have also taken a bit of abuse in dried-out flasks, I am not checking them all, because they are only the stick part of the checker, and the new models don't fit the old.
[SIdebar - And the new hanna checker models self-calibrate. I have been looking for the old ones with the screw adjustment, because adjusting them is a required skill. But now people only stock the new checkers, which you can't calibrate manually and which don't fit the old stick part. Bummer both ways.
Now the students have to calibrate the pH probes with the dataloggers, which have adjustable pH sensor units.]

Back on topic.
So long as it is not distilled water, which damages the ion movement, they will probably be OK. pH 4 buffer seems to be the recommended storage point, and a reasonably strong KCl solution as good/optimal.
Also if they are the liquid filled ones, you may already have saturated KCl for topping up the liquid levels. Although most are gel.
 
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We keep ours (both cabled probes and checker sticks) in small conical flasks with bungs with holes in, so the flask contains enough storage solution to cover the bulb and more. That means even if some does crystalise it takes a long time to dry out enough to put the bulb at risk.
I have some spares in these 'caps' and small bottles but the problem I have with them is 1) the amount of solution is small, so once it starts to dry out there isn't much leeway
and 2) using them (the more cap-like ones) means the solution probably ends up spilled, so you have to refill them. Or best stored upright or they risk leaking.
The flasks remove those issues, although they do take up more space, of course. But they live in the lab and need no tech input apart from visually checking there is enough solution and it is not starting to grow fuzz!
Having read (and been taught in industry) all the warnings about drying them out, I recently found a tray with several old probes, all dried out for at least two or three years, probably many more (past tech turnover - at some point they were rejected as not working and 'stored', but dry) - a bit of cleaning and soaking cycles, and almost all of them are reading fine! They are hardier than I thought!
These were probes, not the checker sticks, although they have also taken a bit of abuse in dried-out flasks, I am not checking them all, because they are only the stick part of the checker, and the new models don't fit the old.
[SIdebar - And the new hanna checker models self-calibrate. I have been looking for the old ones with the screw adjustment, because adjusting them is a required skill. But now people only stock the new checkers, which you can't calibrate manually and which don't fit the old stick part. Bummer both ways.
Now the students have to calibrate the pH probes with the dataloggers, which have adjustable pH sensor units.]

Back on topic.
So long as it is not distilled water, which damages the ion movement, they will probably be OK. pH 4 buffer seems to be the recommended storage point, and a reasonably strong KCl solution as good/optimal.
Also if they are the liquid filled ones, you may already have saturated KCl for topping up the liquid levels. Although most are gel.
We can't buy the buffers for the moment... what I am going to do is prepare a 15% KCl solution and top up the ones with the lowest levels of storage solution. I guess that this is better than nothing.
 
CLEAPSS have a guide on storage of sensor probes with details on how to make your own solutions. It's document TT008.
[ATTACHMENT REMOVED BY MODERATOR - DO NOT SHARE CLEAPSS DOCUMENTS HERE, THEY ARE FOR CLEAPSS MEMBERS ONLY!!!]
 
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We can't buy the buffers for the moment... what I am going to do is prepare a 15% KCl solution and top up the ones with the lowest levels of storage solution. I guess that this is better than nothing.
Just let me convert % to M....
mw 74 - 2M. Can you make it a bit stronger? 22.5%?
You don't need buffer, it they should be fine.
 

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[ATTACHMENT REMOVED BY MODERATOR - DO NOT SHARE CLEAPSS DOCUMENTS HERE, THEY ARE FOR CLEAPSS MEMBERS ONLY!!!]
 
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