Hi there,

You may in theory make a solution of 0.75M tri sodium citrate and then adjut pH with 0.75M citric acid if the pH is actually higher than 7 (which I'm not sure of...). If you do it that way, total citrate will remain 0.75M. Alternatively, I would go for preparing adequat citric acid, mono sodium or di sodium citrate solutions, adjust pH to 7 with NaOH and then adjust final volume so that final citrate concentration is 0.75M.

Hi Dominique,

thanks for the answer! I have a few more questions.

Which molarity of citric acid do you suggest when I want to use citric acid for adjusting the pH? 0.75 M, too?

And what do you mean by adequat citric acid solution? 0.75 M citric acid solution?

We only have tri-soidum citrate (and citric acid) in the lab. Will there be a big difference to mono- or di-sodium citrate? (Actually, the recipe I got only says 0.75 M sodium citrate but nothing about mono, di or tri...)

Hi again,

To keep citrate concentration at 0.75M, you have to use citric acid at 0.75M to adjust pH.

By adequat solution I mean solution containing enough product to get 0.75M citrate at the end (ie. after adjusting the final volume).

If you start from citric acid you will use more NaOH to adjust pH at 7 as you will have to neutralize the three acidic function of citric acid (whereas mono and di sodium have already one and two acidic functions already neutralized, respectively).

https://ar.wikipedia.org/wiki/%D8%B3%D8%AA%D8%B1%D8%A7%D8%AA_%D8%A7%D9%84%D8%B5%D9%88%D8%AF%D9%8A%D9%88%D9%85

Okay, got it. Thanks a lot!

Lena, try this link, it may be helpful:

https://www.aatbio.com/resources/buffer-preparations-and-recipes/citrate-buffer-ph-6