Selectrode--the universal ion-selective electrode-V. Complex formation studies with the Cu(II) Selectrode.

Area of Science:

• Analytical Chemistry
• Coordination Chemistry
• Electrochemistry

Background:

• Accurate determination of metal-ligand complex stability constants is crucial for understanding biological and environmental processes.
• Existing data for copper(II)-EGTA stability constants are limited, necessitating further investigation.

Purpose of the Study:

• To determine the stability constants of copper(II) complexes with glycine and ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA).
• To present methods for calculating chelate complex stability constants using pH and pM data.
• To illustrate the application of the Cu(II) Selectrode in replacement reactions.

Main Methods:

• Calibration of the Cu(II) Selectrode using Cu(II) buffers across various pH levels.
• Determination of stability constants at a fixed ionic strength of 0.1.
• Calculation of stability constants from measured pH and pM values.

Main Results:

• Stability constants for Cu(II)-glycine and Cu(II)-EGTA complexes were successfully determined.
• The obtained values show excellent agreement with previously reported literature data.
• Specific stability constants for the Cu(II)-EGTA system, including logK(Cu, L) = 16.80 and logK(Cu, HL) = 12.56, were determined.

Conclusions:

• The Cu(II) Selectrode is a reliable tool for determining metal-ligand stability constants.
• The study provides valuable and consistent data for the Cu(II)-EGTA system.
• The presented methods are effective for calculating stability constants of chelate complexes.