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

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.