Interlaboratory comparability of copper complexation capacity determination in natural waters

Area of Science:

• Environmental Chemistry
• Analytical Chemistry

Background:

• Accurate determination of copper speciation is crucial for environmental risk assessment.
• Interlaboratory comparability studies are essential for validating analytical methods.

Purpose of the Study:

• To assess the interlaboratory comparability of methods for determining copper complexation capacity (CCC) and copper-ligand complex formation constants.
• To evaluate the suitability of CCC data for regulatory purposes.

Main Methods:

• Eight water samples (six natural, one synthetic ligand, one blank) were analyzed by seven laboratories.
• Laboratories employed their own complexation titration methods.
• Data analysis focused on comparability of CCC and complex formation constants.

Main Results:

• Relatively good comparability was achieved for copper complexation capacity determination across different methods.
• CCC data largely met the 50% agreement criterion.
• Comparability for copper-ligand complex formation constants was poorer, with a wide range (10^7 to 10^12).

Conclusions:

• The study supports the use of copper complexation capacity measurements in environmental copper regulation.
• Further method refinement is needed for reliable determination of copper-ligand complex formation constants.