August 14, 2022, 05:37:46 PM
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Topic: How to stabilize BTB solution for water pH measurement  (Read 265 times)

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Offline kodls

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How to stabilize BTB solution for water pH measurement
« on: August 04, 2022, 03:44:49 AM »
Hello guys,

I use BTB solution for pH and CO2 levels measurement in my fish tank.
It is commonly used technique, try to search "Dropchecker Aquarium"
The solution is 4KH water + 1% BTB 1%inEth. I prepare the 4KH water by mixing 4950gr + 0,6gr NaHCO₃. For the final solution 50gr 1% BTB in ethanol is added to the 4KH water.

This final solution works fine until around a month or so, then the color starts to fade rapidly when stored in PET container and turns yellow.
I tried to aerate the freshly prepared solution which gave it beautiful blue color (honestly it is the best color for use in aquarium since it represents 7-8 pH giving it the best starting point) to remove CO2 and store it in a PET bottle with no air inside. This also did not work.

Do you have any idea ? Should I prime the PET with some base ?

Offline kodls

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Re: How to stabilize BTB solution for water pH measurement
« Reply #1 on: August 05, 2022, 07:43:02 AM »
Here is picture showing (from the left) 3month old solution, 1,5month old solution and fresh solution ???


Offline Corribus

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Re: How to stabilize BTB solution for water pH measurement
« Reply #2 on: August 05, 2022, 08:39:49 AM »
What is BTB?

PET is permeable to gasses (it is why carbonated beverages stored in PET bottles will eventually go flat).
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

Offline kodls

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Re: How to stabilize BTB solution for water pH measurement
« Reply #3 on: August 11, 2022, 03:05:12 AM »
BTB = Bromothymol Blue

Oh, I did not think of that.
Can somebody tell what would be ideal packaging? Must be plastic, glass is not possible  ??? ::)

Offline kodls

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Re: How to stabilize BTB solution for water pH measurement
« Reply #4 on: August 11, 2022, 08:34:50 AM »
Is HDPE better option? Does anyone have an experience ?

Offline Corribus

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Re: How to stabilize BTB solution for water pH measurement
« Reply #5 on: August 12, 2022, 02:19:05 PM »
HDPE would be worse. PET actually has pretty good barrier properties for a polymer. But if you want something basically impermeable, try glass.
« Last Edit: August 12, 2022, 02:38:17 PM by Corribus »
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

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