antigen retrieval in IHC - (Jan/24/2007 )

I need to make up 10mM sodium citrate buffer, pH 6.0 and 9.0 for antigen retrieval. My question is this: does anyone know what the normal pH of this solution is and what do you use to make adjustments to the pH?

we used to have an antigen retrieval sol. with Tris at pH 9.0

we used HCl or NaOH to adjust pH.