Surface Sulfhydryl-functionalized Nanoparticles As Sorbent In Dispersive Solid-Phase Extraction For The Rapid Enrichment Of Mercury Species From Environmental Water Samples

Mercury is a ubiquitous contaminant that is widely dispersed throughout the environment mostly via atmospheric deposition. For different speciation of mercury, the toxicity is significantly difference. Therefore, only monitoring the total mercury concentrations in the environment is not enough, and speciation analysis provides more useful information to assess the toxicity and health risks of mercury and further understand biogeochemical cycling of mercury compounds. But the organic Mercury concentrations of the environmental water samples are very difficult to measure precisely because they are so low and suffer from matrix effects when samples are analyzed directly. Therefore, a sample pretreatment step, which can separate the analytes from the matrix components and preconcentrate them, is exceedingly important.In this study, concentration of mercury species in aqueous solution were determined by high performance liquid chromatography on-line coupled with atomic fluorescence spectrometry (HPLC-AFS) technique. Before enrichment experiments, the method was optimized and validated by determining spiked environmental samples under the optimal condition. The results showed that the present method was rapid, simple and efficient, and can be applied to the determination of mercury species in aqueous solution.The use of magnetic nanoparticles (MNPs) in solid-phase extraction (SPE) has received considerable attention in recent years taking into account many advantages arising from the inherent characteristics of MNPs. The MNPs, together with various coatings applied on their surfaces and functional groups, have been successfully applied to the extract and enrichment a wide range of analytes from environmental water samples.In this study, surface sulfhydryl-functionalized magnetic mesoporous silica nanoparticles (Fe3O4@SiO2-RSH) were prepared, aiming to extract trace alkylmercury from aqueous solution. The prepared nanoparticles were characterized by TEM, ED, EDX, DLS, FTIR, and SERS. Compare with that the non-sulfhydryl-functionalized Fe3O4@SiO2exhibited almost no affinity for methylmercury (MeHg) and ethylmercruy (EtHg); Fe3O4@SiO2-RSH exhibited high adsorption affinity for them, resulting from chelating interaction by surface sulfhydryl group, and the adsorption was not significantly impacted by pH within the range of3.5-9.0or coexisting metal ions. The monolayer adsorption on surface of Fe3O4@SiO2-RSH could reach equilibrium in2min. Moreover, the MeHg and EtHg adsorbed on Fe3O4@SiO2-RSH could be quickly separated from the matrix in a magnetic field and desorbed easily by acetonitrile and L-cysteine aqueous solution or HC1solution. Findings of the present work highlight the potential for using Fe3O4@SiO2-RSH magnetic nanoparticles as effective and reusable adsorbents for extraction of ultra trace alkylmercury from environmental water samples.Conventional magnetic SPE (MSPE) has some inconvenience in separating small amounts of the MNPs from large-volume environmental water samples. Therefore, in this study, the Fe3O4@SiO2-RSH MNPs based dispersive solid-phase extraction method was developed. The goal of this method is the extraction of mercury species from environmental water samples. An interesting aspect of the method is that the MNPs with a sub-30nm size range could be fast and efficiently extracted by0.45μm pore size mixed cellulose esters membrane filter. Thus, the elution step can be conducted by passing small amounts eluent through the MNPs on the membrane. It is also found that addition of Ag+to water sample could improve the elution efficiency, and furthermore, minimizes the matrix effects during the extraction of mercury species from environmental samples. The feasibility of the method was studied, and extraction efficiency was evaluated. The results showed that, calculated at5ng/L spiked concentration levels, absolute recoveries (ARs) were89.4%,91.9%, and64.2%, and enrichment factors (EFs) were596,613, and428, for inorganic mercury (InHg), MeHg, and EtHg, respectively. The high ARs and EFs were achieved in5min of overall extraction time. The method was applied to environmental samples. The results showed that its suitability for use in fast extracting trace levels of mercury species from environmental water samples.