Sizing and quantification of micro- and nanoplastics by single particle ICP-MS: a comparison between quadrupole and high-resolution instruments.

Micro- and nanoplastics (MNPs) are widespread environmental pollutants of growing concern due to their persistence and impacts on ecosystems and human health. Their small size, chemical complexity, and low environmental concentrations make accurate detection and quantification challenging. Single-particle (sp) ICP-MS has emerged as a promising technique for sizing and quantifying small MNPs based on their elemental content, yet the performance of different ICP-MS instrument types remains insufficiently evaluated. In this work, the analytical performance of quadrupole (Q) and high-resolution (HR) spICP-MS was systematically compared for sizing and quantifying metal-doped polystyrene (PS) particles at both the micro- (2.5 μm) and nano-scale (198 nm) by monitoring carbon or metal content. For the analysis of NPs via metal-based detection, both instruments enabled the reliable determination of particle size, particle mass, and mass concentration. The HR system showed enhanced metal sensitivity and improved particle size resolution, while the Q system provided better recoveries of particle number concentration. For the analysis of MPs, spICP-HRMS provided superior sensitivity for metal-based detection, whereas spICP-QMS delivered better carbon-based detection performance and lower size detection limits due to its reduced carbon background. Both techniques underestimated particle mass and number concentrations, reflecting the influence of particle losses, especially pronounced in the HR system, and the need for accurate transport efficiency determination. The use of different data processing tools did not have a significant impact on spICP-MS results. These findings emphasize the importance of carefully selecting the type of ICP-MS instrument, detection approach (metal versus carbon), and calibration strategy for reliable quantification and size characterization of MNPs by spICP-MS.