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.

Single Particle ICP-MS: Advances toward routine analysis of nanomaterials

This tutorial review focuses on the use of ICP-MS based techniques for the analysis of metal-containing nanoparticles and colloids. Within the first part the capabilities of “stand alone” ICP-MS for the analysis of total metal contents and the suitability of stable isotopes for nanoparticle tracking (stable isotope labelling and naturally occurring variation in isotope ratios) are introduced (Chapter 3). Special focus was given on single particle ICP-MS (sp-ICP-MS) mode (Chapter 4). Upon a brief introduction into the theoretical concept, critical aspects such as calibration strategies, dwell time as well as ionic background were discussed and practical advice is given. References to current data assessment sheets are provided. Furthermore, a brief chapter on general sample preparation aspects is included within the first part (Chapter 2). The second part is dedicated to fractionation/separation systems, such as field-flow fractionation (FFF), hydrodynamic chromatography (HDC), high performance liquid chromatography (HPLC) and capillary electrophoresis (CE) coupled on-line with ICP-MS detection for metal-based nanoparticle and colloid analysis (Chapter 5). Each section starts with an introduction into the theoretical concept of the respective fractionation/separation system, followed by practical hints regarding method development (e.g. selection of appropriate carrier/mobile phase, membrane/stationary phase) as well as critical aspects and limitations. Particular attention is payed to laser ablation ICP-MS (LA-ICP-MS) for spatially resolved nanoparticle analysis. Each section concludes with selected application examples of the respective analytical technique from the most relevant fields of nanoparticle use or exposure (consumer products, food, medicine and environment), highlighting the performance of each technique in metal-based nanoparticle analysis. Chapter 6 is dedicated to aspects of quality assurance. Various critical points regarding method development and validation, mass balance, size calibration and quantification from the previous sections are revisited, discussed and practical advice is given. Finally, the authors provide some concluding remarks and future perspectives (Chapter 7). Furthermore, a flow-chart is included as a “hands-on” overview on all ICP-MS based techniques discussed within this tutorial review intended as a “method-decision tool” for users.

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ICP-MS for the analysis at the nanoscale – a tutorial review

In this study, a method for separation, size characterization, and speciation of gold and silver nanoparticles was developed through the use of micellar electrokinetic chromatography (MEKC) coupled to inductively coupled plasma-mass spectrometry (ICP-MS) for the first time. Figures of merit in this proof-of-principle study include peak area precision of 4–6%, stable migration times (1.4% with internal standard), and capillary recoveries on the order of 72–100% depending on species and nanoparticle size, respectively. Detection limits are currently in the sub-microgram per liter range. For example, a total of 1500 50-nm-sized gold nanoparticles were successfully detected. After careful optimization, MEKC-ICP-MS was used to separate engineered nanoparticles (ENPs) of different composition. Speciation analysis of ENPs and free metal ions in solution was feasible using a complexing agent (penicillamine). Gold speciation analysis of a dietary supplement, which contained approximately 6-nm-sized gold nanopartic...

Fast Separation, Characterization, and Speciation of Gold and Silver Nanoparticles and Their Ionic Counterparts with Micellar Electrokinetic Chromatography Coupled to ICP-MS

Single particle inductively coupled plasma mass spectrometry (spICP-MS or SP-ICP-MS depending on the author) is becoming an important tool for the characterization of nanoparticles (NPs). The method allows determining the size, size distribution, and particle number concentrations of NPs in suspensions after a mere few minutes of measurement. This review is modeled after the concept of “an ideal method for atomic spectroscopy” introduced by Gary M. Hieftje in his publication dedicated to Howard Malmstadt. This review discusses the instrumental developments in spICP-MS of recent years step-by-step, from the sample introduction system to the detector. The authors identify necessary improvements and suggest directions for further developments which have the potential to bring the method closer to “an ideal method for atomic spectroscopy”. The review also discusses the literature on coupling spICP-MS to separation and fractionation techniques including capillary electrophoresis (CE), field flow fractionation (FFF), and differential mobility analysis (DMA). The second part of the review is dedicated to the applications of spICP-MS. Key steps in sample preparation and selected instrumental conditions that were used in the published literature are summarized in a tabular form. Most frequently, spICP-MS is used for silver (Ag), gold (Au), and titanium dioxide (TiO2) nanomaterial analysis. Data acquisition was typically performed with millisecond dwell times in the past while a time resolution of hundreds of microseconds has been used more often in the last five years. The table may serve as a guide to choose an experimental procedure depending on the matrix that is present in the sample under investigation.

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A critical review of single particle inductively coupled plasma mass spectrometry – A step towards an ideal method for nanomaterial characterization

The increasing application of engineered nanomaterials (ENMs) in consumer and medical products has motivated the development of single-particle inductively coupled plasma mass spectrometry (spICP-MS) for characterizing nanoparticles under realistic environmental exposure conditions Recent studies have established a set of metrological criteria and evaluated the feasibility of spICP-MS for sizing or quantifying various highly commercialized ENMs However, less is known about the performance of spICP-MS for detecting nanoparticles with sizes greater than 80 nm This paper presents a systematic study on spICP-MS for accurate size measurement of gold nanoparticles from 10 to 200 nm We show that dwell time contributes significantly to the quality of data, with the optimal dwell time that limits split particle events, particle coincidences and false positives being 10 ms A simple approach to correct for split particle events is demonstrated We show that transient features of single particle events can be te

Capabilities of Single Particle Inductively Coupled Plasma Mass Spectrometry for the Size Measurement of Nanoparticles: A Case Study on Gold Nanoparticles

Kwok-On Lui

Papers

Considerations of particle vaporization and analyte diffusion in single-particle inductively coupled plasma-mass spectrometry