Simultaneous multi-element and multi-isotope detection in single-particle ICP-MS analysis: Principles and applications

Single-particle analysis has attracted considerable attention in recent years because of the size/composition-dependent properties and heterogeneity of nanoparticles (NPs). Single-particle inductively coupled plasma mass spectrometry (spICP-MS) is a powerful tool for detecting, characterizing, and quantifying NPs. Generally, in this technique, for NPs, only one element or isotope is monitored in the time-resolved mode. However, the increasing demands for analysis of multi-element engineered and natural NPs have highlighted the importance of the multi-element and multi-isotope analysis of single NPs. Recently, increasing applications have been reported for simultaneous multi-element and multi-isotope detection via spICP-MS techniques, represented by spICP-time of flight (TOF)-MS. In this review, we compare the principles of single-particle multi-element/isotope analysis by using ICP-MS systems equipped with different types of mass analyzers (quadrupole, TOF, and magnetic sector mass analyzers). Furthermore, we highlight the recent advancements in the qualitative characterization and quantitative measurements of NPs, as well as the resulting applications including differentiating between engineered and natural NPs and their source tracing. In particular, single-cell multi-element analysis is also discussed because its principles and applications are very similar to those of single-particle analysis. Based on the current advancements and limitations, future trends are also proposed, including hyphenated techniques to provide complementary information, enriched isotope labeling to track the environmental transformation and bioaccumulation of NPs, and real-time monitoring of NPs with internal standard calibration.