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What's the difference between KH2PO4 and K2HPO4 in MOPS media? - (Jul/17/2008 )

Hi, all.
In the reference to make MOPS media, the K2HPO4 was used. But, I used KH2PO4.
I guessed that there is some differences btw them in pH. but, the pH value to use KH2PO4 is also 7.2.

Is there any problem to grow e coli in the MOPS including KH2PO4 not K2HPO4?



I've never used ' MOPS media' but i'm assuming it's a cell culture media?

If so, then it has the basic components:

- Salt
- Glucose
- Buffer (to maintain a neutral pH)
- Ions

Now KH2PO4 is Potassium Phosphate. It is a salt made of Potassium and Phosphate. It dissolves in water and becomes ions and of course affects the pH.

You could dissove it in:

- water
- Tris-HCl

and on and on and on... but when you do, you WILL affect the pH, even if only slightly...

So...What is the difference between Potassium phosphate and Potassium phosphate in MOPS media?

Potassium phosphate is a solid at room temperature... In MOPS media it is dissolved and becomes ions.

Ussualy, after dissolving something like that in media you'll want to check/adjust the pH as needed.


The difference is partly the number of K+ ions in solution, giving a different ionic strength to the solution. The other difference is the pH will be altered. Ideally you would make solution out of both of them and then combine in appropriate proportions to get the desired pH.


Thanks all.

So if I don't really care about the exact pH value, it doesn't matter if the K2HPO4 or KH2PO4 is used, right?

After I choose the one of them, if the experiments continue with it, it makes sense, right?

I mean I just am wondering if I used the different component from the reference, it can be published or people can trust my experiment even though I mention it in the paper.

I know the best one is that just use the same component from what most people use, but the problem is now that I already have done a lot of experiments with the different chemical from the reference.