Application of 3D printed scavengers for improving the accuracy of single-particle inductively coupled plasma mass spectrometry analyses of silver nanoparticles by dissolved silver removal

Abstract

The determination of silver nanoparticles (Ag NPs) with single-particle inductively coupled plasma mass spectrometry can be severely interfered with coexisting dissolved silver causing high background signals, which can lead to inaccurate quantification of NP size and particle concentration. In this paper, chemically active and reusable 3D printed scavengers are applied for highly efficient dissolved silver removal in Ag NP dispersions, allowing more accurate determination of particle concentration and size. Selective laser sintering was used for constructing the porous 3D scavengers constituting of polystyrene used as a supporting material and ion-exchange material SiliaBond Tosic acid (TA), which were chosen based on their high dissolved silver extraction efficiency and ability to maintain original NP properties. The macroporous structure of the final 3D TA scavengers allowed Ag NPs to pass freely through the object without affecting their original properties. The efficient contact between the sample solution and the functional material resulted in rapid (ca. <1 min/sample), and highly efficient dissolved silver removal (≥98%). The 3D TA scavengers showed potential to be used for preconcentration of dissolved silver, and the retained dissolved silver can be eluted with a 0.5 mM solution of sodium thiosulphate with excellent recoveries (≥99%). Competitive adsorption of elements commonly found in natural waters (Ca, K, Mg, Na, S, Si, and Sr) were not found to affect the dissolved silver extraction efficiency. The developed pre-treatment method was applied for the determination of 30 nm Ag NPs in ultrapure and clear environmental waters with coexisting dissolved silver (0.2 μg kg−1). Whereas measurement of the samples as such led to a significant bias in NP sizing (up to +12% increase) and counting (up to −51% decrease), pre-treatment of samples with the functional 3D TA scavengers eliminated the interfering effect of dissolved silver. This resulted in significant improvement in NP detection and determination. Highly similar values were obtained for both NP mean size (30 ± 1 nm, <4% different) and concentration (<13% different) in all matrices studied as compared to samples in the absence of dissolved silver.