How to make a buffer similar to PBS, pH 8,6? - (Oct/29/2010 )

Hi,
I need to prepare buffer for ELISA, that is possibly closest to PBS, but has pH 8,6. The most important is ion strenth of ions Na+ and K+. Is it possible to keep salts with PO4 3-?
I would be gratefull for any infos,
Greets!

phosphate will not be an effective buffer at pH 8.6. which buffer you use depends on which direction of pH change you need to resist.