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Mercury determination in soil and sludge samples by HR CS GFAAS: comparison of sample preparation procedures and chemical modifiers

Abstract

Mercury (Hg) is an admittedly toxic element. From an analytical viewpoint, Hg volatility makes the preparation of samples containing Hg as well as Hg detection therein a challenging task. The quality of the results is mainly associated with sample pretreatment. Moreover, there are difficulties inherent to thermal stabilization in the graphite furnace during atomic absorption. Here, Hg was determined in different samples (clay soil, sewage sludge, and light sandy soil) by high-resolution continuum source graphite furnace atomic absorption spectroscopy (HR-CS GFAAS). Three different sample preparation methods were investigated: slurry, microwave acid digestion with HF and HNO3 (which resulted in total sample decomposition), and acid leaching with aqua regia. Different chemical modifiers (palladium nanoparticles (PdNPs), Pd(II) solution, gold nanoparticles (AuNPs), and Au(III) solution) were tested, and their efficiencies were compared. Both the slurry method and acid leaching with aqua regia prevented Hg loss and yielded satisfactory results as compared to the certified, indicative or spiked concentrations of all the samples (confidence level 95%), using AuNPs as chemical modifier. The Au-Hg amalgam results of a Hg(II) reduction in AuNPs surface leading to a diffusion and alloying. Hg determination in the sewage sludge sample agreed with certified value for all studied modifiers when the sample is prepared by aqua regia leaching and slurry. Pd(II) solution and PdNPs also provided good results, but in punctual conditions. Pd(II) binds to the analyte, thereby avoiding Hg loss during the pyrolysis step. As for AuNPs, they are an effective modifier because they enhance interaction between the clusters formed after pyrolysis and prevent Hg loss, which confirms the potential application of these modifiers.

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Publication details

The article was received on 15 May 2018, accepted on 03 Jul 2018 and first published on 05 Jul 2018


Article type: Paper
DOI: 10.1039/C8JA00152A
Citation: J. Anal. At. Spectrom., 2018, Accepted Manuscript
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    Mercury determination in soil and sludge samples by HR CS GFAAS: comparison of sample preparation procedures and chemical modifiers

    L. R. R. Souza, M. B. Teixeira, I. A. Luccas and M. Veiga, J. Anal. At. Spectrom., 2018, Accepted Manuscript , DOI: 10.1039/C8JA00152A

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