Simple Automation and Volume Reduction of Voltammetric Measurements for Marine Trace Metal Speciation

This work presents a novel automated voltammetric system that achieves a significant reduction in required sample volume while maintaining measurement quality for trace metal analysis in marine environments. Through modifications to a commercial voltammetric system, including a custom-designed measurement cell and miniaturized reference electrode, the system enables measurements with volumes as low as 1 mL, representing a 90% reduction compared to conventional setups. When integrated with automated sample handling, the system requires 3 mL for concentration measurements and 28.5 mL for complete organic complexation studies—a 70% and 78% reduction, respectively, from traditional methods. The system's performance was validated through copper measurements across diverse sample matrices, including certified reference materials, achieving an average deviation of 8.2% from certified values. Comparative measurements of copper-binding organic ligands in seawater samples demonstrated analytical quality comparable to manual measurements. The automation capabilities reduce analyst labor by up to 89% for concentration measurements and 87% for complexation studies. The system's modular design allows for easy component replacement and adaptation to different measurement procedures. This development particularly enables the investigation of trace metal speciation in sample-limited environments, such as marine porewaters, where traditional voltammetric methods have been constrained by volume requirements. Initial measurements of copper complexation in marine porewaters demonstrate the system's potential for expanding our understanding of sedimentary trace metal cycling.