Noble metal nanocomposites as tools for fast and reliable speciation analysis of mercury in water samples

ABSTRACT

A novel non-chromatographic approach for speciation analysis of mercury was developed based on sequential application of silver and gold nanocomposites as sorbents for solid phase extraction. The nanocomposite materials consisted by AgNPs or AuNPs grafted on submicronsized silica spheres (SiO₂-NH₂@AgNPs and SiO₂-NH₂@AuNPs) were prepared by multistep synthesis procedures and characterised in details by different techniques – Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), electrokinetic measurements, UV–Vis spectroscopy and X-ray diffraction. Excellent separation and enrichment of Hg(II) and CH₃Hg⁺ was achieved due to the specific behaviour and affinity of Ag and Au nanoparticles (NPs) towards particular Hg chemical forms. In the first extraction step, Hg(II) was strongly retained by highly selective amalgamation on the surface of Ag nanocomposite (SiO₂-NH₂@AgNPs). In the second extraction step, CH₃Hg⁺ remained in the supernatant solution was sorbed on the surface of Au nanocomposite (SiO₂-NH₂@AuNPs). Both Hg species trapped in the sorbents precipitates were quantified by electrothermal Atomic Absorption Spectroscopy (AAS) after direct injection in the graphite atomiser under optimal instrumental parameters (Ag and Au act as modifiers). The optimal solid-phase extraction conditions were examined and defined by batch method. Recoveries achieved by the developed analytical procedure were in the range 97–102% for both Hg(II) and methylmercury with limits of detection and quantification of 0.03 and 0.1 µg L⁻¹, respectively. The proposed analytical procedure was applied for speciation analysis of mercury in water samples.

KEYWORDS:

• Mercury speciation
• gold nanoparticles
• silver nanoparticles
• silica submicrospheres
• nanocomposites
• solid phase extraction
• water samples

Acknowledgements

The authors gratefully acknowledge the financial support provided by the Bulgarian National Scientific Foundation (Grant DN 19/10 SmartSpeciation).

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

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