Probing the Environmental Persistence of Inorganic Nanoparticles and Micro(nano)plastics by Single-Particle ICP-MS

The need to better understand the environmental persistence of nanomaterials has driven the development of new analytical methods designed to detect, quantify, and characterize inorganic nanoparticles (NPs) and micro(nano)plastics (MNPs). After two decades of refinement, single-particle inductively coupled plasma mass spectrometry (spICP-MS) has emerged as a powerful analytical technique capable of studying their environmental persistence, by providing high sensitivity, element-specific data on particle size distribution and number concentration. Moreover, spICP-MS can examine NPs/MNPs in environmental samples (i.e., low particle concentrations within complex heterogeneous matrices) where most analytical methods struggle. Herein, we present the underlying analytical principles and current state of spICP-MS, as well introduce the near-term future improvements to the methodology (e.g., multielement detection, enhanced instrumentation) that will enable more sensitive detection, lower particle size limits, and "fingerprinting" of NPs in laboratory studies and environmental samples. We highlight case studies that demonstrate the ability of spICP-MS to elucidate the importance of size, composition, and solution properties in regulating the stability, transformation, and transport of inorganic NPs and MNPs. Throughout, we provide our perspective not only on the unique advantages and success of spICP-MS but also on the challenges associated with existing analytical limits, and indicate scenarios where more experimental studies and instrumentation advances are needed to improve our understanding of NP/MNP persistence.