Church hyb solution questions

[Warren Gallin]

On Mon, 6 Mar 1995, Anthony Tomlinson wrote:

> In article <3j7due$mca at server.st.usm.edu> Glen Shearer,
> gshearer at whale.st.usm.edu writes:
> >
> >Just mix equal molar amounts.  0.5 mole/L monobasic + 0.5 mole/L
> >dibasic and there's your 1M stock.  For the hyb soln' mix up
> 
> surely if you do this the final solution is still 0.5M as the volume is
> double.
> In any case, the pH will not be 7. We mix 1M solutions of the two
> compounds  [stiff deleted]



WARNING: for the Church hybridization buffer the stock solution needs to 
be 1 M in Na+ ions with a pH of 7.2.  If you start mixing up mixtures of 
dibasic and monobasic you will get the right pH, but you will be making 1 
M phosphate, not Na+: this will not give you what you want.

   What you need to do is make up a 0.5 M sol'n of Na2HPO4, but adjust the 
pH down with concentrated phosphoric acid before bringin up to final 
volume.  This will give you the desired pH and Na+ concnetration.