Preparing potassium phosphate buffer(pH 7.4) - (May/12/2006 )
QUOTE (mdfenko @ Sep 28 2006, 11:44 PM)
QUOTE (SnowCasp @ Sep 28 2006, 01:54 AM)
Does it means that I have to prepare two 5mM solutions; one of K2HPO4 and the other of KH2PO4? And then slowly adding the monobasic stock to the dibasic stock untill the req pH is reach?
you can do it this way but you may want to prepare a more concentrated stock and dilute to your final concentration, especially if you have other components in your final buffer.
you can make the concentrated stock by mixing equimolar mono and dibasic until you reach the desired pH.
Thanks for all your help
So I can make a 0.1M of monobasic and dibasic stock.
Mix them together till i get the desired pH.
And dilute the stock from there till the desired concentration
And then add in other addictive to the buffer before use
But someone mentioned that diluting the buffer achieve the desired conc. is not good
M I right to do that??
-SnowCasp-
QUOTE (SnowCasp @ Oct 2 2006, 09:23 PM)
So I can make a 0.1M of monobasic and dibasic stock.
Mix them together till i get the desired pH.
And dilute the stock from there till the desired concentration
And then add in other addictive to the buffer before use
But someone mentioned that diluting the buffer achieve the desired conc. is not good
M I right to do that??
Mix them together till i get the desired pH.
And dilute the stock from there till the desired concentration
And then add in other addictive to the buffer before use
But someone mentioned that diluting the buffer achieve the desired conc. is not good
M I right to do that??
yes, you are correct. but add your other components before making your final dilution.
in most cases, diluting a concentrated stock is fine unless you dilute to the point where the buffering capacity becomes severely diminished. phosphate is a very strong buffer and has good buffering capacity even at 10 mM so your dilution should be fine, especially since you are diluting from 0.1 M (we dilute from 1 M).
that being said, if your additives will influence your pH then you may want to do a final adjustment of pH before, but near, final dilution. you can use an acid or base with a counter ion found with the additives (eg: naoh and/or hcl if nacl is in your buffer).
-mdfenko-