Combination of cloud point extraction with single particle inductively coupled plasma mass spectrometry to characterize silver nanoparticles in soil leachates

Abstract

The expansion of silver nanoparticle (AgNP) applications in industry as antibacterial agents has generated an increment of their presence in the environment. Once there, their behavior is not clear because they can undergo different transformation processes that affect their transport, mobility, bioavailability, and toxicity. Therefore, the characterization and quantification of these emerging contaminants are important to understand their behavior and the toxicity effects that can be exerted on living beings. Single particle inductively coupled plasma mass spectrometry (SP-ICPMS) has demonstrated its ability to characterize and give quantitative information on AgNPs in aqueous samples. However, sometimes, the discrimination of the signal corresponding to AgNPs from the signal of dissolved species (Ag(I)) is a challenge. In the present contribution, it is shown that the presence of high amounts of Ag(I) hamper silver nanoparticle size and nanoparticle concentration determination in aqueous samples by SP-ICPMS. To facilitate signal discrimination of both chemical forms, the combination of cloud point extraction (CPE) with SP-ICPMS was studied. CPE experimental conditions to separate AgNPs from Ag(I) were assessed and adapted taking into account the characteristics of the SP-ICPMS technique. CPE and soil matrix effects on particle size were evaluated, showing that particle size was not modified after being in contact with soil matrix and after being separated by CPE. Additionally, frequently used calculation methods for SP-ICPMS data treatment were assessed. Finally, the potential of the developed methodology CPE-SP-ICPMS was evaluated in aqueous soil leachates contaminated with mixtures of AgNPs/Ag(I)

The Spanish Ministry of Economy and Competitiveness (MINECO) financially supported this work through CGL2013-48802-C3-2-R project (Program 2014) and CTQ2015-68094-C2-1-R project (Program 2015), this last also cofunded by the European Regional Development Fund (FEDER). L. Torrent received a FPI grant from the Spanish Ministry of Economy and Competitiveness (Ref. BES-2014-070625) and a FPI mobility scholarship for her predoctoral stage in the University of Zaragoza (Ref. EEBB-I-17-12391)

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