Mass spectrometry is a valuable tool for detecting and analyzing microplastic pollution in the environment, which poses a serious threat to the ecosystem and human health. This article looks at the various mass spectrometry techniques used in microplastic pollution research, recent advancements, challenges, and future directions.
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The Environmental Hazards of Microplastics: Impacts on Ecosystems and Human Health
Plastics have widespread usage in various industries but have become a major environmental concern due to the accumulation of plastic waste, particularly microplastics.
Microplastics (MPs) are small plastic particles less than 5 mm and have gained significant attention due to their ability to adsorb other contaminants, including hydrophobic pollutants, heavy metals, and organic compounds.
Microplastics pose a persistent threat as they are not easily degraded and can harm ecosystems by releasing harmful plastic additives and forming secondary pollutants. In addition, their large surface area makes them effective carriers of other pollutants, further damaging ecosystems.
Individuals may be exposed to up to 121,000 microplastics annually through inhalation and ingestion, leading to adverse health effects such as chronic inflammation, metabolic disruptions, neurotoxicity, and increased cancer risk.
Analyzing microplastics is crucial for tracing their sources and evaluating their removal from the environment. Understanding the scale of microplastic pollution and developing effective analytical procedures are essential steps in addressing this issue.
Current Analytical Techniques for Microplastic Analysis and Their Limitations
Microscopy is commonly used for microplastic identification but has limitations in sensitivity and accuracy, particularly for smaller particles. It is typically suitable for microplastics larger than 1 mm but may miss smaller particles or misidentify other elements in the sample as microplastics.
Spectroscopic techniques like Raman and infrared spectroscopy can assess microplastic contamination based on particle characteristics but have limitations in identifying polymer composition and additives and analyzing large numbers of particles.
No single technique provides a complete solution, highlighting the need for advancements in more sensitive and accurate techniques for microplastic analysis.
How is Mass Spectrometry Used in Microplastic Pollution Research?
Mass spectrometry is a valuable tool in microplastic pollution research, providing important information about polymer structure, molecular weight, and composition.
Samples are collected from the environment and prepared using thermal decomposition or pyrolysis techniques to release microplastic particles for analysis.
The released particles are then introduced to a mass spectrometer, such as thermal extraction desorption-gas chromatography-mass spectrometry (TED-GC-MS), pyrolysis gas chromatography-mass spectrometry (Pyr-GC-MS), and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS), which can detect the unique chemical fingerprints of the microplastics.
Pyr-GC-MS and TED-GC-MS involve the thermal degradation of microplastics to generate thermal degradation products, which are then captured and analyzed using gas chromatography-mass spectrometry. These methods can identify microplastic polymer types but may not account for physical characteristics and can lead to misjudgment due to similar pyrolysis products from different polymers.
MALDI-TOF-MS is based on the proportionality between the ion fragments' mass-to-charge ratio and the time-of-flight. It can identify the main polymers in microplastics and also analyze their physical characteristics through imaging technology. However, it requires different ionization reagents for different types of microplastics and is not widely used in microplastic detection.
Recent Research and Development
Efficient and Accurate Identification of Microplastics using Thermal Extraction-Desorption and Gas Chromatography-Mass Spectrometry Analysis
A study published in the journal Talanta proposed a new method for identifying microplastics in complex samples using thermal extraction-desorption (TED) coupled with gas chromatography/mass spectrometry (GC/MS) analysis.
Instead of using a small portion of the sample, the researchers pyrolyzed the entire filter with solids collected from water, avoiding sample handling and potential loss. This allowed for high-intensity signals and eliminated inhomogeneity on the filter surface.
This method is efficient, accurate, and cost-effective for identifying microplastics in complex matrices. It has significant implications for microplastic pollution research, as it can help researchers understand the extent and impact of microplastics on the environment more accurately.
Ships' Coatings and Paints Identified as Major Source of Ocean Microplastics
Researchers at the University of Oldenburg's Institute of Chemistry and Biology of the Marine Environment studied microplastic distribution in the North Sea. The results are published in Environmental Science & Technology.
The researchers used pyrolysis–gas chromatography–mass spectrometry/thermochemolysis (Py-GC/MS) to analyze the chemical composition of microplastic particles in water samples. The researchers broke down plastic molecules at 600 oC and separated them by their mass and chemical properties. They discovered that most plastic particles in water samples come from binders in marine paints.
The study indicates that ships contribute significantly to microplastic pollution in the open ocean, indicating a need to address the use of coatings and paints on ships to reduce their impact on marine ecosystems.
Detection and Quantification of Polystyrene Microplastics in Agricultural Areas Using Thermogravimetry Coupled with Mass Spectrometry
In a study published in the Science of The Total Environment, researchers developed a reliable method using thermogravimetry coupled with mass spectrometry (TGA-MS) to quantify polystyrene microplastics (PS-MPs) in the air.
The researchers collected airborne samples from an agricultural area and used TGA-MS to analyze them without extensive treatment. They found that the average concentration of PM10 PS-MPs in an agricultural area was 35.97 ng m-3, mainly derived from agricultural activities.
The study demonstrates the potential of TGA-MS for microplastic characterization in different environments with minimal sample treatment. However, the findings suggest the need for further research on the human health risks posed by PS-MPs in the atmosphere and for developing air quality policies and regulatory instruments.
Challenges and Future Perspectives
The use of mass spectrometry techniques in the analysis of microplastics has become increasingly important in environmental and health research. However, several challenges need to be addressed.
Firstly, identifying and quantifying nanosized plastics remains difficult. Secondly, measuring the low mass of microplastics is a challenge for gravimetric methods. Finally, microplastics mixed with other substances can complicate the analysis.
Despite these challenges, mass spectrometry-based techniques offer a promising approach to studying microplastics in various environments and assessing their potential interactions with living organisms. In particular, multimodal mass spectrometry-based techniques combined with imaging systems can provide detailed information on microplastics' size, shape, and aging and identify chemical additives and other contaminants.
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References and Further Reading
Sorolla-Rosario, D., Llorca-Porcel, J., Pérez-Martínez, M., Lozano-Castelló, D., & Bueno-López, A. (2023). Microplastics' analysis in water: Easy handling of samples by a new Thermal Extraction Desorption-Gas Chromatography-Mass Spectrometry (TED-GC/MS) methodology. Talanta. https://doi.org/10.1016/j.talanta.2022.123829
Dibke, C., Fischer, M., & Scholz-Böttcher, B. M. (2021). Microplastic mass concentrations and distribution in German bight waters by pyrolysis–gas chromatography–mass spectrometry/thermochemolysis reveal potential impact of marine coatings: do ships leave skid marks? Environmental Science & Technology. https://doi.org/10.1021/acs.est.0c04522
Peñalver, R., Costa-Gómez, I., Arroyo-Manzanares, N., Moreno, J. M., López-García, I., Moreno-Grau, S., & Córdoba, M. H. (2021). Assessing the level of airborne polystyrene microplastics using thermogravimetry-mass spectrometry: Results for an agricultural area. Science of The Total Environment. https://doi.org/10.1016/j.scitotenv.2021.147656
Wu, P., Wu, X., Huang, Q., Yu, Q., Jin, H., & Zhu, M. (2023). Mass spectrometry-based multimodal approaches for the identification and quantification analysis of microplastics in the food matrix. Frontiers in Nutrition. https://doi.org/10.3389/fnut.2023.1163823
Huang, Z., Hu, B., & Wang, H. (2023). Analytical methods for microplastics in the environment: a review. Environmental Chemistry Letters. https://doi.org/10.1007/s10311-022-01525-7
Chun, S., Muthu, M., & Gopal, J. (2022). Mass Spectrometry as an Analytical Tool for Detection of Microplastics in the Environment. Chemosensors. https://doi.org/10.3390/chemosensors10120530
Velimirovic, M., Tirez, K., Verstraelen, S., Frijns, E., Remy, S., Koppen, G., ... & Vanhaecke, F. (2021). Mass spectrometry as a powerful analytical tool for the characterization of indoor airborne microplastics and nanoplastics. Journal of Analytical Atomic Spectrometry. https://doi.org/10.1039/D1JA00036E