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

Importance of the Topic

Microplastics have become pervasive contaminants in aquatic ecosystems, raising concerns over their impact on wildlife and human health. Reliable identification and quantification of these particles in surface waters are essential for environmental monitoring and pollution mitigation.

Objectives and Study Overview

This study demonstrates an integrated workflow combining automated sample preparation, Fourier transform infrared spectroscopy (FTIR) and pyrolysis-gas chromatography mass spectrometry (Py-GC-MS) to characterize microplastics extracted from river water. The goals are to streamline pretreatment, enhance reproducibility and obtain both particle-level and mass-based compositional data.

Methodology and Instrumentation

Samples were collected from a river and subjected to automated oxidative digestion, density separation and filtration using the MAP-100 device. Extracted particles in the size range 0.3–5 mm were first analyzed by FTIR with an attenuated total reflectance accessory (ATR) to obtain qualitative identification and particle counts. A subset of particles was homogenized by cryogenic grinding (IQ MILL-2070) with silica aid to ensure uniform size distribution. Approximately 10 mg of ground sample was introduced into a multi-shot pyrolyzer (EGA/PY-3030D) interfaced with GCMS-QP2020 NX. Calibration was performed using an 11-component microplastics standard (MPCS) and internal standard (chryserin d-12).

Main Results and Discussion

FTIR-ATR analysis identified 78 microplastic particles: 79.5 % polypropylene (PP), 14.1 % polyethylene (PE) and 6.4 % ethylene–vinyl acetate (EVA). Particle densities were calculated based on a 15 m3 water volume.

Py-GC-MS quantification detected PP, PE, polystyrene (PS) and EVA. Calibration curves exhibited limits of quantification down to 0.64 µg (PS) and limits of detection below 0.2 µg. Quantitative results for four river samples averaged 58.8 µg PP, 36.0 µg PE and 2.30 µg EVA per 10 mg of ground material, corresponding to a total recovery of approximately 82 %. Relative standard deviations ranged from 1.7 % to 11.4 %, confirming sample uniformity and analytical precision.

Benefits and Practical Applications

• The MAP-100 automation reduces hands-on time and improves reproducibility in particle isolation.
• FTIR-ATR offers rapid, non-destructive polymer identification and particle counting.
• Py-GC-MS provides sensitive, mass-based quantification even for mixed polymer samples.
• Combined approaches deliver complementary data for comprehensive microplastics assessment.

Future Trends and Applications

Advancements may include: development of high-throughput screening platforms, expansion of spectral and pyrolysis libraries to cover emerging polymers, coupling with imaging systems for size distribution analysis, and standardization of methods across laboratories to support regulatory monitoring.

Conclusion

This integrated workflow combining MAP-100 sample preparation, FTIR-ATR screening and Py-GC-MS quantification delivers robust, reproducible identification and mass-based analysis of microplastics in river water. The complementary techniques enable both particle-level and quantitative mass information, supporting reliable environmental monitoring.

Instrumentation Used

• Sample Preparation: Microplastic Automatic Preparation Device MAP-100
• FTIR Analysis: IRSpirit-TX spectrometer with QATR-S diamond ATR accessory
• Cryogenic Grinding: IQ MILL-2070 Cryogenic Mill
• Pyrolysis-GC-MS: EGA/PY-3030D Multi-Shot Pyrolyzer; GCMS-QP2020 NX with UAMP-K01 column kit

References

• Application News No. 01-00522: Analysis of Microplastics in Environmental Water Using MAP-100 and FTIR
• Application News No. GCMS-2202: Automated Workflow for Quantitative Analysis of Microplastics via Pyrolysis-GC/MS