PBS for dissolving MTT - Should PBS without potassium be used for dissolving MTT powder (Dec/16/2009 )

Hello everyone,
I found out that in my lab there is a trend of using special PBS lacking potassium ions for dissolving MTT powder. Is there any advantage of doing so, I asked some of the friends here, they replied thats the trend here, so looking for answers from you all.
The method for preparing PBS for MTT followed here is:
Na2HPO4.12H20 0.716gm in 10ml deionized water (0.2M/L)
NaH2PO4.2H20 0.332gm in 10ml deionized water (0.2M/L)

Mix 8.1ml Na2HPO4 + 1.9ml NaH2PO4
Adjust pH to 7.4
In 10 ml above mixture add 1.75gm NaCl
Add qs deionized water to make 200ml solution

Many of you might be using MTT kit so no need to prepare the solution, however I guess some of you might be making solution on their own, so please share your ideas. Thank you

I have always used normal PBS and it works!

Thank you
I also started with the normal PBS when i did not get any reasons for using the special PBS for the purpose, since MTT can be dissolved in a whole lot of things i did not find any reason for not using normal PBS, thanks a a lot for replying though.