Electrochemical Detection of Ultratrace (Picomolar) Levels of Hg²⁺ Using a Silver Nanoparticle-Modified Glassy Carbon Electrode

Abstract

Ultratrace levels of Hg²⁺ have been quantified by undertaking linear sweep voltammetry with a silver nanoparticle-modified glassy carbon electrode (AgNP-GCE) in aqueous solutions containing Hg²⁺. This is achieved by monitoring the change in the silver stripping peak with Hg²⁺ concentration resulting from the galvanic displacement of silver by mercury: Ag(np) + 1/2Hg²⁺(aq) → Ag⁺(aq) + 1/2Hg(l). This facile and reproducible detection method exhibits an excellent linear dynamic range of 100.0 pM to 10.0 nM Hg²⁺ concentration with R² = 0.982. The limit of detection (LoD) based on 3σ is 28 pM Hg²⁺, while the lowest detectable level for quantification purposes is 100.0 pM. This method is appropriate for routine environmental monitoring and drinking water quality assessment since the guideline value set by the US Environmental Protection Agency (EPA) for inorganic mercury in drinking water is 0.002 mg L^-1 (10 nM).