Evaluation of Nanoparticle Tracking Analysis (NTA) for the Measurement of Nanoplastics in Drinking Water

Abstract In the last few years, microplastics have been detected in fresh- and seawater, atmosphere, sediments, soils, sewage sludge, biota and food. However, these microplastics can degrade to even smaller plastic particles in the sub-micron range, the nanoplastics. Only a few studies so far confirmed the presence of NP in environmental samples and their release during the use of personal care products, the boiling of plastic teabags and the use of plastic infant bottles. Due to their smaller dimensions and colloidal properties, nanoplastics could pose an increased hazard to the environment, biota and humans. While there are methods for detecting microplastics, the reliable detection and quantification of size and particle number concentrations of plastic particles less than a micrometre in size are still difficult. In this study, the performance characteristics of nanoparticle tracking analysis (NTA) for detecting nanoplastics using an NS300 instrument were determined after optimisation. The NS300 proved to be accurate and precise for a 102 nm Nanospheres suspension, showing favourable results for accuracy, repeatability and reproducibility at high and low particle number concentrations. While the concentration range was linear from 5.0x106 to 2.0x109 particles/mL, the particle size range of the NS300 instrument was linear from 46 to >350 nm. From the measurements of mixtures of particles, it is clear that NTA has difficulties with polydisperse mixtures resulting in an underestimation of the smaller particle sizes. Finally, eight brands of bottled mineral water were analysed. The particle number concentrations ranged from 1.0x106 to 2.2x107 particles/mL, with mean particle sizes in the range of 110 to 170 nm and mode particle sizes <100 nm for all samples. Particle size distributions showed a particle size range of 50 to 500 nm.