Buffering & chelating metal ions

[Jeff Krause]

Greetings All,

  Two quick questions regarding the formulation of physiological
buffers containing metal ions. 1) I've heard tell of a database of
metal ion stability constants somewhere on the net and would very
much like to find it. Can you tell me where it is? 2) I am trying 
to find the crown ether compound (+)-18-crown-6-tetracarboxylic acid
which is a barium chelator. Can you tell me who sells it?
  All assistance is greatly appreciated, thanks in advance.

Jeff Krause