# Good containers for storing PH pen calibration solution



## ForestDave (9 Mar 2021)

Hi 
Sorry, probably a stupid question but I don't want to get it wrong.
I'm wondering what's the best container for storing the ph pen buffer solutions, glass or plastic? I've got a couple of old honey jars but they have metal lids and wondered whether this is an issue. Would a plastic food container be a better option or is the plastic likely to affect the solution as well?
Thanks


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## Hanuman (9 Mar 2021)

Plastic. You don't want to contaminate the solution. It's a reference solution so it should be kept as pristine as possible. In fact why are you even changing the solution from the original container?


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## aquascape1987 (9 Mar 2021)

I’d leave them in what they came in and store them somewhere dark and cool. If the reason that you are looking for storage containers is because they are opened sachets rather than bottles, it’s worth mentioning that sachets are supposed to be for one calibration only, and are designed to be disposed of afterwards


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## Zeus. (9 Mar 2021)

Best done fresh every time you calibrate, Tried saving them and they just get mould growing in them


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## ForestDave (9 Mar 2021)

Thanks guys. 
Yep. I had two sachets come with the pen. I’ll order up some bottles. Do the pens need calibration every time you use them or can you get away with once a week? Also has anyone tried any diy solutions like baking soda or are they not worth bothering with?
Cheers


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## dw1305 (9 Mar 2021)

Hi all, 


ForestDave said:


> Also has anyone tried any diy solutions like baking soda or are they not worth bothering with?


It is possible, <"but quite tricky">. We buy them for work, rather than making them up ourselves. 

They need to be <"buffers">. Chemical buffers are specific combinations of conjugated weak acid and weak base, meaning they aren't as straightforward to make as conductivity standards etc.  

cheers Darrel


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## Hanuman (9 Mar 2021)

ForestDave said:


> Do the pens need calibration every time you use them or can you get away with once a week?


Technically you don't need to recalibrate them every single time but if you do you will get the most accurate results. It is advised to calibrate regularly though.

In fact no so long ago I had problems with a PH pen that I bought recently. It was giving me wonky results from one test to the next in the same solution in just a matter of minutes. What I did to overcome this was to calibrate the probe every time I made a measurement so basically I did 10 calibrations in 20 minutes. Obviously you should not be doing this but it's the only way I found to have consistent results. The probe is obviously bad so I send it for checking.


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