A metal-ion buffer provides a controlled source of free metal ions in a manner similar to the regulation of hydrogen ion concentration by a pH

buffer Buffer may refer to: Science * Buffer gas, an inert or nonflammable gas * Buffer solution, a solution used to prevent changes in pH * Buffering agent, the weak acid or base in a buffer solution * Lysis buffer, in cell biology * Metal ion buffer * ...

A metal-ion buffer solution contains the free (hydrated) metal ion along with a

complex compound A coordination complex consists of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as ''ligands'' or complexing agents. Many ...

formed by the association of the ion with a

ligand In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electr ...

in excess. The concentration of free metal ion depends on the total concentration of each component (ligand and metal ion) as well as on the stability constant of the complex. If the ligand can undergo

protonation In chemistry, protonation (or hydronation) is the adding of a proton (or hydron, or hydrogen cation), (H+) to an atom, molecule, or ion, forming a conjugate acid. (The complementary process, when a proton is removed from a Brønsted–Lowry acid, ...

, the concentration of the free metal ion depends also on solution pH. A considerable improvement in the detection limit of a liquid-membrane

ion-selective electrode An ion-selective electrode (ISE), also known as a specific ion electrode (SIE), is a transducer (or sensor) that converts the activity of a specific ion dissolved in a solution into an electrical potential. The voltage is theoretically dependent ...

has been achieved by using a metal-ion buffer as internal solution.Pretsch, E. (2007
The new wave of ion-selective electrodes
''Trac-Trends Anal. Chem.'' 26, 46-51

References

Inorganic chemistry Acid–base chemistry Equilibrium chemistry Buffer solutions {{Physical-chemistry-stub