Improving Environmental Microplastic Extrapolation: From Field of View to Full Sample, and from Microplastic 2D‐Morphology to Mass

Microplastic (MP) analysis via microspectroscopy typically examines only 1-10% of filter substrates due to time constraints, requiring reliable extrapolation methods for quantitative environmental monitoring. Current subsampling strategies suffer from heterogeneous particle dispersion, leading to 50-80% error in MP quantification. Additionally, MP researchers require enhanced environmental MP mass datasets, necessitating reliable conversion algorithms from two-dimensional morphological data to mass estimates. This study introduces an area-based extrapolation technique that compares the MP-to-generic particle area ratio within a rectangular field of view against total particle area on the entire filter membrane, combined with a simplified morphology-to-mass conversion model (Hagelskjær model). First, two Sphagnum moss samples were analyzed using Raman microspectroscopy and critical angle darkfield illumination microscopy. Results demonstrated stable MP concentrations (17% RSD [n = 8]) despite heterogeneous generic particle distribution (31% RSD [n = 8]), with mean particle-area coverage of 2.4% per subsample. Then, twenty MP fragment subsamples (10 µm to 1500 µm) were used to calibrate the height multiplier (Mh) which ranged from 0.26 to 0.47 (mean: 0.34 ± 0.05, 15% RSD), establishing that particle height equals approximately one-third of the minimum Feret diameter with this simplified plane-particle model. These methods enable MP quantification and mass estimation from limited spectroscopic analysis.