PH Probe Storage Fluid

[EnglishRebel]

I just purchased a portable PH/temp probe. The instructions say to put some storage fluid in the cap when not in use. Is it permissible to use 7.0 PH buffer solution for this purpose or just RO/DI water?
Thanks

[Randy Holmes-Farley]

Yes, that would be fine. Just remember it is phosphate based, so rinse it before putting the probe in the tank. pH 4 buffer is also fine and typically has no phosphate in it. Diluted tank water is also fine. :)

FWIW, I keep mine in my sump 24/7. :)

[EnglishRebel]

<a href=showthread.php?s=&postid=14508453#post14508453 target=_blank>Originally posted</a> by Randy Holmes-Farley
Yes, that would be fine. Just remember it is phosphate based, so rinse it before putting the probe in the tank. pH 4 buffer is also fine and typically has no phosphate in it. Diluted tank water is also fine. :)

FWIW, I keep mine in my sump 24/7. :)

Thanks Randy. So just don't let it dry out. BTW I can't keep mine in the sump as it floats. :p (It's a Hanna Testers pHep 4).

[Randy Holmes-Farley]

OK, happy reefing. :)

[loudell]

The best storage fluid would be 3M KCL in a 50/50 mix of distilled water and #4.0 pH calibration fluid.
If you leave the probe in RO/DI the fluid will draw most of the salt from the internal reference fluid thus shortening the life of the probe greatly.

[EnglishRebel]

<a href=showthread.php?s=&postid=14509185#post14509185 target=_blank>Originally posted</a> by loudell
The best storage fluid would be 3M KCL in a 50/50 mix of distilled water and #4.0 pH calibration fluid.
If you leave the probe in RO/DI the fluid will draw most of the salt from the internal reference fluid thus shortening the life of the probe greatly.
How can it do this as I thought the electrode was encased in plastic? Isn't distilled water essentially the same as RO water anyway?
Confused. :confused: Randy??

[Yogre]

I have the same meter. I'll have to get the manual out, but I dimly remember the manual saying not to use RO/DI water for storage.

[Randy Holmes-Farley]

The probe tip is glass (except in some very unusual probes), and that glass is somewhat permeable ions (it has to be as that is how it works), so yes, Lou is correct, storage in totally pure water will draw out the ions that need to be inside the tip.

FWIW, you folks may not know it, but Lou is the owner of American Marine/Pinpoint, so take his comments in light of expected knowledge of how pH meters work. :)

[EnglishRebel]

<a href=showthread.php?s=&postid=14515804#post14515804 target=_blank>Originally posted</a> by Randy Holmes-Farley
The probe tip is glass (except in some very unusual probes), and that glass is somewhat permeable ions (it has to be as that is how it works), so yes, Lou is correct, storage in totally pure water will draw out the ions that need to be inside the tip.

FWIW, you folks may not know it, but Lou is the owner of American Marine/Pinpoint, so take his comments in light of expected knowledge of how pH meters work. :)

Oooh sorry Lou. :( The instructions that came with it said to use their storage fluid. Would 7.0 buffer and distilled be okay or just use salt (tank) water as Randy suggested?
Thanks

[loudell]

Alan, You want to call the manufacturer to see specifically what they would recommend, I will say that most pH probes are made basically the same. Here is a list in descending order of the fluid that I would recommend for storage:
-probe storage fluid-you can make it or purchase it
-#4.0 pH calibration fluid
-#7.0 pH calibration fluid

Do not store pH probes in Reverse osmosis or deionized water
Tap water is not great depending on your local water chemistry

By your description the device that you have is a pH Pen. This is where the probe is a part of the plastic housing that holds the electronics. The problem with pH pens is:
-The amount of electrolyte inside the probe tip is very small. When this fluid(or gel) is sufficiently diluted the probe will no longer function. In your case the entire pen will no longer function
-You can not continuously monitor. Your probe will spend most of its time in storage. You should probably use storage fluid to extend it's life
Let us know how it works out....

[Biologist]

Here's some commercial storage solution if you don't want to or can't make the KCl solution.-

http://www.fishersci.com/wps/portal/PRODUCTDETAIL?productId=4620977&catalogId=29101&pos=5&catCode=SE_SC&fromCat=yes&keepSessionSearchOutPut=true&brCategoryId=null&hlpi=y&fromSearch=Y

You can make some yourself using something like this-
"For longer term storage (more than 24 hr) the probe should be immersed in a pH 4 buffer containing 10 g of KCl for every 100 mL of buffer solution."

[EnglishRebel]

<a href=showthread.php?s=&postid=14516862#post14516862 target=_blank>Originally posted</a> by loudell
Alan, You want to call the manufacturer to see specifically what they would recommend, I will say that most pH probes are made basically the same. Here is a list in descending order of the fluid that I would recommend for storage:
-probe storage fluid-you can make it or purchase it
-#4.0 pH calibration fluid
-#7.0 pH calibration fluid

Do not store pH probes in Reverse osmosis or deionized water
Tap water is not great depending on your local water chemistry

By your description the device that you have is a pH Pen. This is where the probe is a part of the plastic housing that holds the electronics. The problem with pH pens is:
-The amount of electrolyte inside the probe tip is very small. When this fluid(or gel) is sufficiently diluted the probe will no longer function. In your case the entire pen will no longer function
-You can not continuously monitor. Your probe will spend most of its time in storage. You should probably use storage fluid to extend it's life
Let us know how it works out....

Lou
Yes it's a pen type. They recommend storing it in their HI 70300 solution. The electrode is replaceable but I want to ensure it's good to go when I need to do a FW dip of new fish (which is why I purchased it). I'll order a bottle of storage solution -- it's only $11.99 for 220ml.
Thanks for the help.

[yraveh]

while discussing the pH probes, I would like to understand the following observation:
my pinpoint pH probe responses fast to a change in pH and within seconds I get a stable reading. However after measuring a saturated lime and then putting the probe back in sump it takes many minutes to drift back to stable reading of the pH. Is that normal? why does it happen?

[loudell]

could be a few things...
Older probes react slower than newer, cleaner probes
Might need a cleaning (diluted muriatic) for a minute or two
Of the many minutes it takes to get back does it reach 90% of the end reading in a short amount of time?

[yraveh]

I just looked at the time course.

@ time 0 probed moved to sump after being in lime with pH 12.17 (~2).
At 1 min- pH= 9.22; 2 min- 8.88; 3 min-8.64;
4 min-8.51; 5min-8.45; 6 min-8.43. Final reading is 8.34.

So is that normal?

[Randy Holmes-Farley]

Did you rinse it?

A fine coating of limewater on the probe will take time to dissolve and/or may precipitate calcium carbonate or magnesium hydroxide locally.

Also, it does normally take some time for pH meters to equilibrate with the solution. Protons are actually diffusing into and out of a thin hydrated surface region of the glass and that is not instantaneous. The larger the pH difference between the before and after, and the less strongly buffered is the second solution, the slower that process will be. :)