From its early beginnings in characterizing aerosol particles to its recent applications for investigating natural waters and waste streams, single particle inductively coupled plasma-mass spectrometry (spICP-MS) has proven to be a powerful technique for the detection and characterization of aqueous dispersions of metal-containing nanomaterials. Combining the high-throughput of an ensemble technique with the specificity of a single particle counting technique and the elemental specificity of ICP-MS, spICP-MS is capable of rapidly providing researchers with information pertaining to size, size distribution, particle number concentration, and major elemental composition with minimal sample perturbation. Recently, advances in data acquisition, signal processing, and the implementation of alternative mass analyzers (e.g., time-of-flight) has resulted in a wider breadth of particle analyses and made significant progress toward overcoming many of the challenges in the quantitative analysis of nanoparticles. This review provides an overview of spICP-MS development from a niche technique to application for routine analysis, a discussion of the key issues for quantitative analysis, and examples of its further advancement for analysis of increasingly complex environmental and biological samples. Graphical Abstract Single particle ICP-MS workflow for the analysis of suspended nanoparticles.

The utilization of microsecond dwell times allows for the detection of multiple elements within a single particle.

Environmental context. The detection and characterisation of engineered nanomaterials in the environment is essential for exposure and risk assessment for this emerging class of materials. However, the ubiquitous presence of naturally occurring nanomaterials presents a unique challenge for the accurate determination of engineered nanomaterials in environmental matrices. New techniques and methodologies are being developed to overcome some of these issues by taking advantage of subtle differences in the elemental and isotopic ratios within these nanomaterials.Abstract. The increasing manufacture and implementation of engineered nanomaterials (ENMs) will continue to lead to the release of these materials into the environment. Reliably assessing the environmental exposure risk of ENMs will depend highly on the ability to quantify and characterise these materials in environmental samples. However, performing these measurements is obstructed by the complexity of environmental sample matrices, physiochemical processes altering the state of the ENM and the high background of naturally occurring nanoparticles (NNPs), which may be similar in size, shape and composition to their engineered analogues. Current analytical techniques can be implemented to overcome some of these obstacles, but the ubiquity of NNPs presents a unique challenge requiring the exploitation of properties that discriminate engineered and natural nanomaterials. To this end, new techniques are being developed that take advantage of the nature of ENMs to discern them from naturally occurring analogues. This paper reviews the current techniques utilised in the detection and characterisation of ENMs in environmental samples as well as discusses promising new approaches to overcome the high backgrounds of NNPs. Despite their occurrence in the atmosphere and soil, this review will be limited to a discussion of aqueous-based samples containing ENMs, as this environment will serve as a principal medium for the environmental dispersion of ENMs.

This tutorial review focuses on aqueous slurries of dispersed engineered nanoparticles (ENPs) used in chemical mechanical planarization (CMP) for polishing wafers during manufacturing of semiconductors.

A recreational water system was monitored for release of both mineral and organic sunscreen constituents for the first time.

The rapid development of nanotechnology has led to concerns over their environmental risk. Current analytical techniques are underdeveloped and lack the sensitivity and specificity to characterize these materials in complex environmental and biological matrices. To this end, single particle ICP-MS (spICP-MS) has been developed in the past decade, with the capability to detect and characterize nanomaterials at environmentally relevant concentrations in complex environmental and biological matrices. However, some nanomaterials are composed of elements inherently difficult to quantify by quadrupole ICP-MS due to abundant molecular interferences, such as dinitrogen ions interfering with the detection of silicon. Three approaches aimed at reducing the contribution of these background molecular interferences in the analysis of (28)Si are explored in an attempt to detect and characterize silica colloids. Helium collision cell gases and reactive ammonia gas are investigated for their conventional use in reducing the signal generated from the dinitrogen interference and background silicon ions leaching from glass components of the instrumentation. A new approach brought on by the advent of microsecond dwell times in single particle ICP-MS allows for the detection and characterization of silica colloids without the need for these cell gases, as at shorter dwell times the proportion of signal attributed to a nanoparticle event is greater relative to the constant dinitrogen signal. It is demonstrated that the accurate detection and characterization of these materials will be reliant on achieving a balance between reducing the contribution of the background interference, while still registering the maximum amount of signal generated by the particle event.

The recent expansion in the use of nanomaterials in consumer and industrial applications has led to a growing concern over their behavior, fate, and impacts in environmental systems. However, engineered nanoparticles comprise only a small fraction of the total nanoparticle mass in aquatic systems. Human activities, particularly in urban watersheds, are increasing the population of incidental nanoparticles and are likely altering the cycling of more abundant natural nanoparticles. Accurate detection, quantification, characterization, and tracking of these different populations is important for assessing both the ecological risks of anthropogenic particles, and their impact on environmental health. The urban portion of the South Platte watershed in Denver, Colorado (United States) was sampled for zinc to identify and quantify different nanomaterial sources. Single particle ICP-QMS was employed, to provide single elemental (Zn) signals arising from particle detection events. Coupling spICP-QMS to sample pre-fractionation (sedimentation, filtration) provided some insights into Zn association with nanoparticulate, colloidal, and suspended sediment phases. Single particle ICP-TOFMS (spICP-TOFMS) provided quantification across a large atomic mass range, yielding an even more detailed characterization (elemental ratios) on a particleby-particle basis, providing some delineation of multiple sources of particles. Across the watershed, on average, 21% of zinc mass was present as zinc-only particles with a rather uniform mean size of 40.2 nm. Zinc that was detected with one or more other elements, primarily Al, Fe, and Si, is likely to be present as heteroagglomerates or within mineral colloids. Although spICP-TOFMS provides a substantial amount of information, it is still in its early stages as an analytical technique and currently lacks the requisite sensitivity to study the smallest of nanoparticles. As this technique continues to develop, it is anticipated that this methodology can be broadly applied to study sources, behavior and effects of a disparate variety of nanoparticles from both geogenic and anthropogenic origins.

Current approaches provide a view of natural nanomaterials while emerging technologies open the door to further studies of nanogeoscience.