Optical photothermal infrared spectroscopy with simultaneously acquired Raman spectroscopy for two-dimensional...

Area of Science:

• Analytical Chemistry
• Environmental Science
• Materials Science

Background:

• Microplastic pollution is a growing concern, necessitating advanced detection and identification methods.
• Vibrational spectroscopy, including Fourier transform infrared (FTIR) and Raman microspectroscopy, shows promise for microplastic analysis.
• Existing methods face challenges in reproducibility and comprehensive identification across different instruments.

Purpose of the Study:

• To evaluate the effectiveness of optical photothermal infrared (O-PTIR) spectroscopy for microplastic identification.
• To develop and validate a novel two-dimensional identification (2D-HQI) approach combining IR and Raman spectral data.
• To assess the O-PTIR method's performance against established FTIR and Raman spectrometers.

Main Methods:

• Simultaneous acquisition of IR and Raman spectra of nine common polymers using an O-PTIR microscope in reflection mode.
• Comprehensive spectral band assignments for the analyzed plastics.
• Inter-system comparison using hit quality index (HQI) and development of a 2D-HQI approach.
• Preparation and analysis of microplastic particles using the developed 2D-HQI framework.

Main Results:

• O-PTIR successfully acquired IR and Raman spectra for polyethylene, polypropylene, PVC, PET, polycarbonate, polystyrene, silicone, PLA, and PMMA.
• The study established agreement between O-PTIR and standalone FTIR/Raman spectrometers.
• The 2D-HQI approach demonstrated enhanced material identification capabilities for microplastic particles.
• Successful application of the 2D-HQI method to microplastic samples prepared by wet grinding.

Conclusions:

• The O-PTIR spectroscopic technique is a viable tool for microplastic particle analysis.
• The developed 2D-HQI framework significantly improves the accuracy and reliability of microplastic identification.
• This approach offers a robust solution for detecting and identifying microplastics in complex matrices like environmental, food, and biological samples.