DIY KCl 4M for pH electrode storage

[MrClockOff]

Hi there

I’m looking to make my own KCl 4M storage solution and I wonder if using potassium sorbate in such solution is a good idea. Thinking of preventing mold formation and not damaging pH electrode in any way. Also I’m going to use RO water.

By the way I’m using Hanna pH meter.

Cheers

 

[dw1305]

Hi all,

I'm looking to make my own KCl 4M storage solution and I wonder if using potassium sorbate in such solution is a good idea.

You don't need anything else.

Nothing will grow in 4 mol. KCl, it is pretty "salty".

Cheers Darrel

 

[Laoshan]

Interesting question. I bought KCl for the same purpose. I thought 3 mol/l is the standard concentration for the pH pen storage solution?

Not sure if it matters much.

 

[MrClockOff]

Nothing will grow in 4 mol. KCl, it is pretty "salty".

That makes absolute sense despite the fact that some stock solutions sold online contain some mould inhibitors (If we believe what description says)

Interesting question. I bought KCl for the same purpose. I thought 3 mol/l is the standard concentration for the pH pen storage solution?

Not sure if it matters much.

Yeah, when I was doing research I found that some solutions are 4M and some are 3M. I guess the more concentrated the better + as @dw1305 says nothing would grow in such strength solution.

 

[MrClockOff]

@dw1305 I’ve seen you have mentioned on another thread that KCl can be used as an additive to test sample to improve pH reading results. Could you please elaborate on this a little bit more? For example if water has low TDS or hardness what KCl concentration we should aim for to improve reading quality?

Many thanks

 

[dw1305]

Hi all,

@dw1305 I’ve seen you have mentioned on another thread that KCl can be used as an additive to test sample to improve pH reading results. Could you please elaborate on this a little bit more?

Because it is a neutral salt it doesn't effect pH, all it does is lessen the time the electrode takes to reach equilibrium.

This means you don't need to add a set amount, just tip a small amount of salt into the sample. Details below for DI water.

<"https://assets.thermofisher.com/TFS...s/pH-level-dispensed-ultrapure-SNWPPHPURE.pdf">4

..... pH measurements of ultrapure water tend to be unstable and can be inaccurate due to its low ionic strength and low buffering capacity; therefore, pH is not considered a measurement of ultrapure water quality. The ASTM Standard Specification for Reagent Water, D1193*, which establishes water quality standards for laboratory use, does not list pH readings for Type I, II or III water. ....

..... pH measurements of ultrapure water tend to be unstable and can be inaccurate due to the low ionic strength and low buffering capacity of ultrapure water.The addition of a neutral salt (KCl) will increase the ionic strength, and minimize drift and bias in the pH measurement. For example, the addition of 0.3 mL of saturated KCl to 100 mL of ultrapure water will stabilize the reading without significantly impacting the pH.

Cheers Darrel

 

[MrClockOff]

Hi all,

Because it is a neutral salt it doesn't effect pH, all it does is lessen the time the electrode takes to reach equilibrium.

This means you don't need to add a set amount, just tip a small amount of salt into the sample.

Cheers Darrel

Thanks a lot!