Magnetic solid phase extraction of silver-based nanoparticles in aqueous samples: Influence of particle composition and matrix effects on its application to environmental samples and species-selective elution and determination of silver sulphide nanoparticles with sp-ICP-MS.

Silver-based nanoparticles (Ag-b-NPs) are currently a cause for concern because they are being produced in increasing quantities for use in industrial goods and consumer products. This goes hand in hand with their release to the environment and the resultant risks for the entire ecosystem. Therefore, it is essential that these materials are monitored. A promising technique that overcomes a number of shortcomings in handling environmental samples is magnetic solid phase extraction (MSPE) of Ag-b-NPs, which is applied in this study. It has been possible to extract different kinds of Ag-b-NPs at environmentally relevant concentrations in the low ng L range using iron oxide magnetic particles (IOMPs) of different size and shape with efficiencies in the range from 80 to 100%. Furthermore, environmentally relevant inorganic ions and TiO particles exhibited no major effect on the extraction efficiency. However, natural organic matter (NOM) exhibited a significant influence from 1 mg L resulting in a 50% drop in extraction efficiency. This effect could be overcome by adding 10 mM Ca or increasing the iron oxide magnetic particle (IOMP) concentration to 500 mg L. Applying the presented procedure, Ag-b-NPs added to a river water sample at β = 50 ng L were successfully extracted. We also investigated the coextraction of Ag, demonstrating that NOM could eliminate coextraction. The subsequent species-selective elution of AgS-NPs after MSPE, was carried out based on ethylene diamine tetraacetate (EDTA) as eluent in different matrices. A desorption efficiency of 76 ± 6% could be achieved while preserving the AgS-NPs' size. By contrast, core Ag-NPs and AgCl-NPs are dissolved if the presented method is followed.