I am wondering why there are two recipes to prepare 10X pbs, one for adjust ph value to 7.4, and the other one is to let the ph value remain around 6.8 after solving the salts. The latter one claims that the ph 6.8 will alter to around 7.4 after the 10 fold dilution, which is unnecessary to adjust ph when preparing 1X pbs.
I am wondering which illustration is correct. In my experience, I do see the ph change after 10 fold dilution. But how could it be possible? I mean we always adjust the ph value before adjusting volume while preparing various solution. How can the ddH2O change the ph value significant?
the relative ref are shown below
1. Ph can change after 10 fold dilution of 10xpbs https://www.sigmaaldrich.com/TW/en/support/calculators-and-apps/10x-phosphate-buffered-saline
2. ph won’t change after 10 fold dilution of 10x pbs
https://www.thoughtco.com/phosphate-buffered-saline-pbs-solution-4061933
thanks a lot
The pH change for a buffer solution upon dilution is something thoroughly discussed in RG. See for example:
https://www.researchgate.net/post/How_can_dilution_affects_the_pH_of_a_buffer_solution
Because usually the pH will not change much.
If you make a 800 mL buffer solution, adjust the pH, and complete to 1000 mL, the change in pH is meaningless.
If you dilute 10-fold, the change will be considerable. And the change depends on the dilution factor and the initial buffer concentration.
Then, for carefully designed experiments do not make too concentrated buffers.
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