The occurrence of microplastics in many, if not all environmental compartments is a matter of increasing concern and deserves proper attention. However, there is still a lack of analytical tools for straightforward monitoring of these tiny plastic particles at environmentally relevant levels in water. Inductively coupled plasma-mass spectrometry (ICP-MS) operated in single-particle mode (SP-ICP-MS) was demonstrated to be a powerful technique for the characterization of metallic nanoparticles, but to the best of the authors' knowledge, SP-ICP-MS has not yet been evaluated for the purpose of detection of microplastics and their quantitative determination (particle number density). In this work, spherical polystyrene microspheres of 1 and 2.5 μm – to mimic microplastics coming from plastic waste – have been detected using ICP-MS. The approach developed relies on the ultra-fast monitoring of transient signals (with a dwell time of 100 μs) when using a quadrupole-based ICP-MS unit in the so-called single-event mode and registering the signal spikes produced by individual microparticles by monitoring the signal intensity at a mass-to-charge ratio (m/z) of 13 (¹³C⁺). The accuracy of the number-based concentration results (particle number densities) has been assessed by comparing the number of events detected when monitoring ¹³C⁺ to those detected when monitoring ¹⁶⁵Ho⁺ for 2.5 μm lanthanide-doped polystyrene beads. Additionally, the results obtained for both polystyrene microspheres in terms of size (most frequently occurring intensity of the signal distribution) compare well with the size as determined using electron microscopy. ICP-MS operated in single-event mode thus allows information on both the size distribution and mass concentration of microplastics to be obtained. As this approach makes use of instrumentation already available in many routine labs analyzing environmental samples, it can enable these labs to analyze microplastics by using their instrument in single-event mode.

Development of analytical methods for the characterization (particle size determination, chemical identification, and quantification) of the low μm-range microplastics (MPs; 1–10 μm) and nanoplastics (NPs; 1 nm to 1 μm) in air – coarse (PM₁₀; <10 μm), fine (PM_2.5; <2.5 μm) and ultrafine (PM₁; <1 μm) particulate matter – is a quickly emerging scientific field as inhalation has been identified as one of the main routes of human exposure. The respiratory tract may serve as both target tissue and port of entry to the systemic circulation for the inhaled MPs and NPs with their small particle size. As an outcome, the interest of the scientific community, policy makers, and the general public in indoor airborne MPs and NPs increased tremendously. However, there is a lack of detailed knowledge on the indoor and outdoor sources of MPs and NPs, their levels, and their health impact. This is mainly related to a lack of standardized sampling and analytical methods for size determination, chemical identification, and quantification. In this review, recent developments in mass spectrometry-based analytical methods for size determination, chemical identification, and quantification of the MPs and NPs in indoor air and dust, are discussed.