What we need is a thorough explanation of why one or the other concentration of phosphate salts is correct for mammalian tissue for TEM in procedures such as the DAB process. I would so much appreciate help in logically settling this argument around here. The primary function of a buffer is to set and hold the pH at the desired level. M of the phosphates is normally used with mammalian tissues and the addition of salts to a fixative is usually not required.
M buffer with the addition of that salt is certainly hypertonic.
Soerenson developed the phosphate based buffer recipe. 0.01M is about the minimum effective buffer concentration for fixatives. That level without salt is commonly used for plants since they have much lower osmolarity than mammals do. This is osmotically correct for human serum. The Gibco catalog gives two formulations for PBS on page 2.9 of their 1997 catalog.