A comparison of spectroscopic analysis methods for microplastics: Manual, semi-automated, and automated Fourier transform infrared and Raman techniques.

This study was conducted to establish the best practice for microplastic analysis by reducing the time demand and human bias and comparing the characteristics of μ-FTIR and Raman techniques. A manual analysis, semi-automated method, and fully automatic identification method were compared. Fully automated identification took the shortest time to analyze a whole filter paper (Ø25 mm), but its false positive identification rate was 80 ± 15%. The semi-automated analysis using spectrum profiling was suitable for all aspects of microplastic analysis. It was less time consuming than the manual analysis (manual: 6.1 ± 0.8 h, semi-automated: 4.0 ± 0.6 h), and 22 ± 12% more microplastic particles were detected using the semi-automated method compared to the manual analysis due to the reduction in false negative results. Raman microscopy was suitable for small microplastic (>5 μm) identification, although the Raman analysis took nine times longer than the semi-automated analysis.