Question

Q:Why is it preferable to use a metal ion buffer to achieve pM = 9, rather than just dissolving enough M to give a 10-9 M solution?

Answer 1

A metal ion buffer solution contains the free/hydratd metal ion along with the complex fomed by the association ion with the ligand in excess. Thus the concentration of free metal ion depends on the total concentration of each component as wel as on the stability constant of the complex.

Thus metal ionbuffer has the advantages

i)of accurately measuring the activity/concentration of the free(hydrated) ion

ii) reduces the effect of dilution or changes of the concentration of metal ions,due to loss or contamination.

iii) has sufficient pH buffer capacity.

Thus the metal ion buffer resists change in pM value by the addition of small amounts of metal ion or ligand with which the metal ccan complex.