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Sequential combination of micro-FTIR imaging spectroscopy and pyrolysis-GC/MS for microplastic quantification.
Nadia Bouzid1, Bruno Tassin1, Johnny Gasperi2
1Leesu, Universite Paris Est Creteil, Ecole des Ponts, Institut Polytechnique de Paris, F-94010 Creteil, France. rachid.dris@u-pec.fr.
Analytical Methods : Advancing Methods and Applications
|April 28, 2025
Summary
This study combined micro-Fourier-transform infrared spectroscopy (μ-FTIR) and pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) for microplastic analysis in river sediments. Results showed consistent mass concentrations but differing polymer proportions, highlighting method-specific limitations.
Area of Science:
- Environmental Science
- Analytical Chemistry
- Polymer Science
Background:
- Microplastic (MP) quantification in environmental samples like sediments is challenging due to method-specific interferences.
- Micro-Fourier-transform infrared spectroscopy (μ-FTIR) and pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) are common but have limitations for complex matrices.
Purpose of the Study:
- To develop and validate a sequential analysis protocol combining μ-FTIR and Py-GC/MS for microplastics (10-500 μm) in river sediments.
- To compare the performance and identify limitations of μ-FTIR and Py-GC/MS for quantifying specific polymers (PE, PP, PS).
- To provide guidelines for selecting appropriate methods based on research objectives.
Main Methods:
- Sequential analysis of microplastics (10-500 μm) in 16 river sediment samples using μ-FTIR and Py-GC/MS.
- Mass concentration estimation via μ-FTIR particle volume and direct measurement by Py-GC/MS with internal calibration.
- Comparative analysis of results, including polymer proportions and intra-site variability.
Main Results:
- Consistent mass concentrations were observed between μ-FTIR and Py-GC/MS across sites, with concentrations ranging from 0.2 to 17 μg g⁻¹ (μ-FTIR) and 0.8 to 21 μg g⁻¹ (Py-GC/MS).
- Significant discrepancies in polymer proportions were found: μ-FTIR showed a predominance of polypropylene (PP), while Py-GC/MS detected more polystyrene (PS).
- Intra-site variability was primarily influenced by sample preparation, with measurement technique playing a lesser role.
Conclusions:
- The combined μ-FTIR and Py-GC/MS approach provides reliable microplastic mass concentration data in river sediments.
- Differences in polymer detection highlight the limitations of each method, particularly μ-FTIR's reduced ability to detect synthetic fibers and abrasion particles.
- Method selection should be guided by research focus, considering the strengths and weaknesses of μ-FTIR and Py-GC/MS for specific microplastic types.
