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“It can be concluded that simultaneous acquisition of IR and Raman spectra of MP particles with the O-PTIR instrument is a superior approach for material identification in terms of throughput than two standalone instruments.”
The authors report on a significant advancement in microplastic detection methodology, addressing the critical challenge of reliable polymer particle identification in environmental samples. Böke et al. demonstrate that traditional approaches using separate FTIR and Raman spectroscopy measurements often lead to ambiguous identification results, particularly when particles contain additives, pigments, or environmental contamination. The researchers developed a two-dimensional identification approach using O-PTIR technology to overcome these limitations through simultaneous acquisition of complementary IR and Raman spectra.
The authors report excellent spectral agreement between O-PTIR measurements and standalone instruments, with hit quality index (HQI) values ranging from 0.7 to 0.96 for IR spectra and 0.72 to 0.97 for Raman spectra when comparing nine different polymer types. The researchers demonstrate that O-PTIR spectra collected in reflection mode correspond well to transmission-mode FTIR spectra, while maintaining submicron spatial resolution advantages. Comprehensive band assignments were successfully obtained for all tested polymers.
The authors report successful application of their two-dimensional HQI approach to real microplastic particles prepared by wet grinding, demonstrating robust identification capabilities. The researchers show that combined IR and Raman analysis effectively ruled out false identifications that might occur with single-technique approaches, such as potential misidentification between PVC and PET based on IR spectra alone. The study demonstrates successful detection of particles down to 6 μm diameter, overcoming spatial resolution limitations of traditional IR microscopy.
The authors conclude that O-PTIR represents a superior analytical approach for microplastic identification, offering unprecedented throughput advantages through simultaneous dual-mode acquisition. The technique’s ability to provide submicron resolution without Mie scattering artifacts, combined with complementary chemical information from both spectroscopies, enables more accurate and reliable polymer identification than conventional approaches.
Julia Sophie Böke et al
Leibniz Institute of Photonic Technology
