Analysis of microplastic particles by using single particle inductively coupled plasma mass spectrometry

A method based on single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) with the use of regular sample introduction system was developed for the study of microplastics released from consumer products. With the standard type nebulizer used in SP-ICP-MS, the effect of sample introduction rate was evaluated and the flow rate of 0.18 mL min⁻¹ was selected for further use. Under this condition, the transport efficiency was determined by using a commercially available uniform size of 50 nm AuNPs, and the calibration graph was constructed by using sucrose as dissolved forms of carbon. With this calibration approach, size analysis of polystyrene particles in the range of 1 – 6 µm was performed with the size detection limit of approx. 400 nm. The SP-ICP-MS was then applied to determine the particle size of laboratory synthesized polystyrene latex. The sizes obtained were found to positively deviate from the reference sizes reported by scanning electron microscopy (SEM), suggesting the potential problem from matrix interferences. Therefore, particle washing method by using deionized water was proposed to purify the polystyrene particles from their suspending medium. After particle washing, the sizes obtained from SP-ICP-MS with correction factor agreed well with the reference sizes. Therefore, the SP-ICP-MS method was applied to investigate the microplastics released from teabags and disposable face masks with the results compared with those from dynamic light scattering (DLS) and SEM.