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Engineered nanomaterials are used increasingly around the world. In recent years, environmental concerns have being raised that call for risk assessment, toxicity studies, and nanosafety policies. It is therefore important to provide analytical tools that are able to characterize various types of nanomaterials in a sensitive and fast fashion. In this study, the analytical performance of three sample introduction systems, a PFA micronebulizer with a Peltier-cooled cyclonic spray chamber (PC3), a PFA micronebulizer with a heated cyclonic spray chamber and three-stage Peltier-cooled desolvation system (APEX Q), and a monodisperse droplet generator (Microdrop) with an in-house built spray chamber, was compared for the characterization of silver nanoparticles (Ag NP) with different sizes (20–100 nm) using single particle inductively coupled plasma mass spectrometry (SP-ICP-MS). With continuous polydisperse and pulsed monodisperse droplet sample introduction, single 30 nm NP (PC3) and 20 nm NP (APEX Q, Microdrop), respectively, were successfully detected. Detection efficiencies (20–100 nm Ag NP) were in the range of 5.8 × 10−5 to 8.2 × 10−5 counts per atom, cpa (PC3), 7 × 10−5 to 9.5 × 10−5 cpa (APEX Q), and 8.1 × 10−5 to 1.2 × 10−4 cpa (Microdrop). For a given nanoparticle sample, the variation of the relative standard deviation (RSD) of the size distribution width among the three systems was found to be 1–4% (e.g. 1.3% for 100 nm Ag NP with RSDs of 16.3%, 16.8%, and 17.6% for Microdrop, APEX Q, and PC3, respectively). Size measurements performed by SP-ICP-MS were validated by transmission electron microscopy measurements. Because silver toxicity depends on the silver species in the sample, simultaneous detection of Ag NP and free Ag(i) ions was studied with droplet sample introduction. [ABSTRACT FROM AUTHOR]

Methods to detect, quantify, and characterize engineered nanoparticles (ENPs) in environmental matrices are highlighted as one of the areas of highest priority research needs with respect to understanding the potential environmental risks associated with nanomaterials. More specifically, techniques are needed to determine the size and concentration of ENPs in a variety of complex matrices. Furthermore, data should be collected at environmentally and toxicologically relevant concentrations. Both single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) and asymmetrical flow field flow fractionation (AF4) ICP-MS offer substantial advantages for detecting ENPs and assessing many of the above parameters in complex matrices over traditional characterization methods such as microscopy, light scattering, and filtration. In this study, we compared the ability of two emerging techniques to detect well characterized, monodisperse silver ENPs and examined their overall applicability to environmental studies specifically with respect to their: (A) size and concentration detection limits, (B) resolution and (C) multi-form elemental analysis. We find that in terms of concentration detection limit (both, on a mass basis and particle number basis) SP-ICP-MS was considerably more sensitive than AF4-ICP-MS (ng L−1vs.μg L−1, respectively), and offers the unique ability to differentiate dissolved and nanoparticulate fractions of total metal. With a variety of optimization parameters possible, AF4-ICP-MS can detect a much smaller NP size (2 nm vs. 20 nm for SP-ICP-MS), provides the possibility for greater size resolution. [ABSTRACT FROM AUTHOR]