Material Analysis of Microplastics in River Water - FTIR and Pyrolysis-GC-MS Analysis

Importance of the Topic

Microplastics (MPs) are recognized as a significant environmental hazard due to their small size and potential effects on aquatic ecosystems. Reliable identification and quantification methods are essential for assessing contamination levels in rivers, lakes, and oceans. Rapid and reproducible analysis supports monitoring efforts and informs pollution mitigation strategies.

Objectives and Study Overview

The study demonstrates an integrated workflow combining automated sample pretreatment with MAP-100, Fourier Transform Infrared Spectroscopy with Attenuated Total Reflectance (FTIR-ATR), and Pyrolysis-Gas Chromatography-Mass Spectrometry (Py-GC-MS) to characterize microplastics collected from river water. Key goals include improving reproducibility, enabling mixed-plastic analysis, and quantifying plastic types in environmental samples.

Methodology and Instrumentation

• Sample Collection and Pretreatment: River water samples were processed using the MAP-100 automatic microplastic preparation device. Pretreatment involved oxidative digestion with hydrogen peroxide, density separation using sodium iodide solution, and overflow extraction to isolate MPs in the 0.3–5 mm size range.
• FTIR-ATR Analysis: Extracted particles were analyzed non-destructively with the IRSpirit-TX spectrometer and QATR-S diamond ATR unit. Spectral libraries allowed identification of environmentally degraded plastics. Particle counts and density per cubic meter of water were determined.
• Freeze Grinding: Collected MPs were homogenized with silica grinding aid in the IQ MILL-2070 cryogenic mill to ensure uniform particle size for GC-MS analysis.
• Py-GC-MS Analysis: Homogenized samples were analyzed using the EGA/PY-3030D Multi-Shot Pyrolyzer coupled to the GCMS-QP2020 NX. Calibration standards comprising 12 plastic types were used to build quantitative models via F-Search MPs software.

Main Results and Discussion

• FTIR-ATR identified 78 microplastic particles in a 15 m3 water volume, with polypropylene (PP) accounting for 79.5%, polyethylene (PE) 14.1%, and ethylene-vinyl acetate (EVA) 6.4%.
• Py-GC-MS confirmed consistent identification of PP, PE, polystyrene (PS), and EVA. Quantitative analysis of a ~10 mg sample yielded a total plastic mass of 97.2 μg, corresponding to an estimated 1.9 mg of MPs in the original sample, with recovery rates around 82%.
• Limits of detection and quantification were established (LOQ: 0.64–4.26 μg; LOD: 0.19–1.28 μg), demonstrating the method's sensitivity. Relative standard deviations of 1.6–11.4% indicate good reproducibility.

Benefits and Practical Applications

• Automated pretreatment reduces manual workload and enhances reproducibility.
• FTIR-ATR enables rapid, non-destructive screening of individual particles and determination of number-based concentration.
• Py-GC-MS provides sensitive mass-based quantification of mixed plastic types and high throughput for small sample volumes.
• The combined workflow supports comprehensive monitoring of microplastic pollution in environmental waters.

Future Trends and Opportunities

Advancements in automation, spectral libraries, and data analysis algorithms will further improve throughput and accuracy. Integration with imaging techniques and coupling to high-resolution mass spectrometers can expand detection to nanoplastics. Standardized protocols across laboratories will facilitate large-scale environmental surveys and regulatory compliance.

Conclusion

The integrated MAP-100, FTIR-ATR, and Py-GC-MS workflow offers a robust platform for the qualitative and quantitative analysis of microplastics in river water. High reproducibility, sensitivity, and the capacity to analyze mixed plastics make this approach suitable for environmental monitoring and research into plastic pollution dynamics.

References

• Ayaka Miyamoto et al. Material Analysis of Microplastics in River Water – FTIR and Pyrolysis-GC-MS Analysis. Shimadzu Application News No. 01-00806-EN, 2025.
• Shimadzu Application News No. 01-00522: Analysis of Microplastics in Environmental Water Using MAP-100 and FTIR.
• Shimadzu Application News No. GCMS-2202: Automated Workflow for Quantitative Analysis of Microplastics via Pyrolysis-GC/MS.