What Goes Around\nShould Not Move Around: Immobilizing\nMicroplastics as a New Approach for Analytical Ring Trials

Microplastics have gained importance as pervasive environmental\nparticulate pollutants. Their analysis demands precise quantification\nmethods, with interlaboratory comparisons (ILCs) being crucial for\nperformance assessment. Typically, ILCs follow a parallel design:\nparticipants each analyze their own sample specimen, often with significant\nvariability due to challenges in producing identical subsamples of\nthe particulate analyte, inseparably masking the relevant uncertainty\nsources the ILC intends to measure. We provide a filtration-immobilization\napproach for particles ≤100 μm, creating permanently\nimmobilized microplastics samples. This enables serial ILC designs\nwhere participants sequentially measure the same sample. Demonstrating\nthe concept using 5 polymers immobilized on 10 μm pore-sized\nsilicon filters, we expose the specific measurement uncertainty being\n77% lower than the total combined uncertainty observed in a parallel\nILC (relative standard deviations: 5 and 23%, respectively). Particle\nimmobilization opens further applications in sample archiving and\ncreation of durable reference samples also for other fields of particulate\nmatter research beyond microplastics.