Magnetic solid-phase extraction of trace-level mercury(II) ions using magnetic core-shell nanoparticles modified with thiourea-derived chelating agents

We describe a method for magnetic solid phase extraction of trace-levels of Hg(II) ions by using Fe3O4 nanoparticles (NPs) covered with a shell of silica and modified with the chelator N-(2-acetylaminoethyl)-N'-(3-triethoxysilylpropyl)thiourea. The new magnetic NPs enable rapid magnetic separation, thus leading to higher efficiency and accuracy. The extracted Hg(II) ions on the NPs were directly quantified using a mercury analyzer. Possible interferents are widely eliminated in this highly selective extraction process, and the NPs are not exerting an interfering effect either. The method has an enrichment factor of 100, and extraction recoveries are between 95 and 107 % when using 10 mg of the extracting NPs. The method works over a wide range of pH values and can be applied to even complex natural samples. The effects of pH value, extraction time, sample volume and adsorbent amount on the extraction efficiency were optimized. Under the optimal conditions, the detection limit is as low as 17 ng L-1. The method was applied to the preconcentration and detection of Hg(II) in three natural water samples using the standard addition method.