Towards field trace metal speciation using electroanalytical techniques and tangential ultrafiltration.

Area of Science:

• Environmental Chemistry
• Analytical Chemistry

Background:

• Trace metal speciation is crucial for understanding metal behavior in aquatic environments.
• Existing methods can be complex and not suitable for on-site analysis.

Purpose of the Study:

• To develop and validate a portable methodology for on-site trace metal speciation.
• To determine total, free, and ultrafiltered metal fractions using electrochemical methods and ultrafiltration.

Main Methods:

• Electrochemical techniques: Stripping Chronopotentiometry (SCP) for total metal and Absence of Gradients and Nernstian Equilibrium Stripping (AGNES) for free metal.
• Tangential ultrafiltration (UF) with a 1 KDa membrane to separate metal fractions.
• Method validation using Cadmium (Cd2+) spiking in natural river water samples.

Main Results:

• Achieved low limits of detection (LOD) for Cd2+: 1.6×10⁻⁹ M (SCP) and 1.9×10⁻⁹ M (AGNES).
• SCP showed 96% recovery for total metal determination compared to GF-AAS.
• Identified differences in metal complexation in river samples, suggesting the presence of small inorganic ligands in Sorocabinha river water.

Conclusions:

• The proposed UF and SCP/AGNES methodology is effective for on-site trace metal speciation.
• Provides accurate total and free metal concentrations.
• Offers insights into the role of small inorganic ligands in metal complexation in natural waters.