On the Limitations and Challenges to the Analysis of Microplastic Particles in Complex Environmental Matrices
This week (10-14 March 2025) the 2025 National Water Monitoring Conference (NWQMC) took place in Green Bay, Wisconsin. Microtrace Research Microscopist Otyllia Vercelletto presented a paper entitled, “On the limitations and challenges to the analysis of microplastic particles in complex environmental matrices” at the Aquatic Debris Session: Breaking Down the Facts: Measuring, Monitoring, and Mitigating for Microplastics. The paper was co-authored by Ms. Vercelletto, M.S., Christopher S. Palenik, Ph.D., and Peter Lenaker. The paper explores Microtrace’s research that has been under development for a period of several years, aimed toward the isolation, characterization, and identification of microplastics in both sediment and complex water matrices. This presentation will present the method, validation efforts, benefits, and limitations of this process.
Abstract
On the limitations and challenges to the analysis of microplastic particles in complex environmental matrices
Otyllia Vercelletto, M.S., Christopher S. Palenik, Ph.D., Peter Lenaker
While the presence of microplastics in the environment is unquestioned, the isolation, characterization, and identification of microplastics in both sediment and complex water matrices represents a challenging prospect. The isolation of microplastics from a sample is complicated by the wide particle size distribution of the sediment relative to the microplastic particle size and the presence of tenacious organic matter which shares a similar density range to that of common microplastic polymers. Directly counting and categorizing microplastic particles by purely visual methods, such as light microscopy, can be subjective. For instance, when conducted manually, the recognition of microplastics particles is biased towards larger, higher contrast, or colored particles. Additionally, polymer identification methods are often decoupled from particle counts, and the inherent process of identifying polymers in a time efficient and comprehensive manner faces numerous analytical challenges. For example, dark particles such as tire rubber don’t typically provide a useful FTIR reflectance spectrum, and oxidized polymer surfaces can produce fluorescence which overwhelms weak Raman scattering.
The literature presents numerous “complete” methods that typically ignore key details and challenges throughout the process. Alternatively, other methods only treat specific challenges and account for only a discrete portion of the overall process. Lacking from our searches of the literature is a holistic method that attempts to balance the challenges of being (a) complete, (b) objective, (c) reproducible, (d) quantitative, and (e) time-conscious.
There is no perfect approach; however, a comprehensive understanding of such limitations can help to determine a workflow appropriate to a particular set of goals. Here we discuss those challenges and a method that has been under development for a period of several years, aimed toward identifying and acknowledging these limitations, minimizing the impact of the above challenges, and maximizing speed, reproducibility, and objectivity. This approach is discussed in three stages: particle isolation, analysis, and data interpretation and has been applied to a set of validation samples as well as a set of environmental samples. This presentation will present the method, validation efforts, benefits, and limitations of this process.
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