Solid phase extraction materials as a key for improving the accuracy of silver nanoparticle characterization with single-particle inductively coupled plasma mass spectrometry in natural waters through dissolved silver removal

The accurate characterization of silver nanoparticles (Ag NPs) in environmental samples is crucial for understanding the potential impact of these materials on the environment and human health. Single-particle inductively coupled plasma mass spectrometry (spICP-MS) is one of the few techniques available for quantifying NPs at environmentally relevant concentrations. However, the spICP-MS detection of Ag NPs can be interfered with coexisting dissolved analyte causing high background signals, which mask NP signals leading to a significant bias in NP characterization. In this paper, a simple sample pre-treatment procedure for efficient removal of dissolved silver in natural waters is proposed using solid phase extraction (SPE) materials, allowing more accurate characterization of NPs in environmental water matrices. The applicability of eight commercially available SPE materials was evaluated based on their effects on sample Ag NP properties and dissolved silver extraction efficiency in environmental waters, which were shown to depend on sample matrix. The SPE materials found most efficient in dissolved silver extraction were further studied for improving the characterization of 30 nm Ag NPs in colorless and dark-colored waters. Whereas dissolved silver concentrations of ≤1 μg kg−1 were shown to lead to a significant bias in NP characterization (up to +58% increase in NP size and − 90% decrease in particle concentration), pre-treatment of the samples with SPE materials ‘SiliaMetS Thiol’ and ‘Purolite C115HMR’ minimized the effect of dissolved silver interference. As a result, highly more accurate NP sizing (28 ± 2 nm) and relatively stable particle concentration was obtained for 30 nm Ag NPs in environmental waters.