Statistical Analysis for Quality Control of Monodispersed Polystyrene Particles Certified Reference Materials

Monodispersed polystyrene latex (PSL) particles serve as certified reference materials (CRMs) for ensuring quality, method validation, and calibration of particle size measuring instruments. They were produced in compliance with ISO 17034:2016 standards. However, limitations arise in the quality control of CRM characteristics due to challenges in synthesizing particles of consistent size across multiple batches. It is widely recognized that variations in particle size homogeneity between batches can occur in the particle manufacturing process even when conducted under identical conditions and ingredients. This paper aims to explain and demonstrate statistical analyses conforming to ISO Guide 35:2017 used for quality control and certifying reference values for monodispersed polystyrene particles. The procedure can be divided into three steps: 1) preliminary check by using dynamic light scattering (DLS), 2) preliminary check by using transmission electron microscopy (TEM), and 3) final homogeneity testing, along with short-term and long-term stability assessment and characterization. The described protocol can control the quality of particles from multiple batch productions by establishing criteria at each step to ensure particle size consistency. The certified value of a 100 nm diameter monodispersed polystyrene particle produced by the National Institute of Metrology, Thailand (NIMT) is 105.5 ± 4.6 nm, acceptable for measurement traceability for testing and calibration services. Keywords: Quality control, polystyrene particles, certified reference materials