Sampling and pre-treatment effects on the quantification of (nano)silver and selected trace elements in surface water - Application in a Dutch case study

Detection and quantification of trace elements in aqueous samples is crucial in terms of environmental monitoring and risk assessment for (heavy) metals in the environment. Silver (Ag) in its nanoparticulate form is commonly used as antimicrobial additive in consumer products and pharmaceuticals. Since released dissolved Ag species act as the actual antimicrobial agent, Ag nanomaterials are supposed to pose risks to the environment by a release of dissolved species. Unfortunately, no standard protocols exist yet to gain reliable information about the presence and distribution of nanomaterials in the environment. Therefore, we present an interlaboratory collaboration involving three laboratories to quantify silver, silver based nanoparticles (Ag-b-NPs) and a wide range of relevant trace elements after different sample pre-treatments for profiling surface water of a Dutch channel. Besides quantification of the elements, different sample pretreatments like acidification, with or without filtration, and their effect on the measurable elemental content were studied. Total Ag and Ag-b-NPs were quantified at lower ng L⁻¹ range in the channel water whereas reasonable differences depending on the pre-treatment were identified; Ba, As, Pb, Co, Cr, Cu, Ni and Zn were detected at μg L⁻¹ range and Na, K, Mg, Ca and Fe at mg L⁻¹ range. Significant sample pre-treatment effects were observed for the elements Cr, Cu, Fe, Pb and Zn, which is very likely due to the existence of particulate species. Measured concentrations were well comparable among the three laboratories underpinning method validity and correctness allowing for a comprehensive, reliable risk assessment for nanomaterials in the environment.