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A Simple Sample Preparation Method to Significantly Improve Fourier Transform Infrared (FT-IR) Spectra of Microplastics

Applied Spectroscopy 2022 15 citations ? Citation count from OpenAlex, updated daily. May differ slightly from the publisher's own count.
Alexander Matthew David Finnegan, Rebekah Süsserott, Lip-Hwee Koh, W. B. Teo, Chris Gouramanis

Summary

Researchers developed a simplified fiber-pressing method for FT-IR analysis of microplastics that presses fibers to under 10 µm thickness without requiring KBr powder, and validated it on atmospheric microplastic samples from Singapore and Phnom Penh. They found that the method increased the proportion of fibers achieving a library match score of 80% or higher from 51% with unpressed fibers to 98% with pressed fibers.

Spectroscopic analysis has become an essential part of the rapidly growing field of microplastic (MP) research. Here, we introduce a simple sample preparation method that dramatically improves results from Fourier transform infrared (FT-IR) analysis of MP and other environmental fibers. Our method provides cost-effective, reliable, high-quality spectra that achieve high-matching scores to polymer libraries. The efficacy of this method is demonstrated with two environmental datasets from Singapore and Phnom Penh that were collected while sampling for atmospheric MPs. The method developed and applied in this study is a simplification of the KBr method, where the analyzed fiber is pressed to a thickness of <10 μm; however, no KBr powder is required. For the combined dataset, 379 non-pressed fibers were analyzed with 193 (51%) returning a search score of ≥80% (chosen minimum search score threshold) and 259 pressed fibers, with 254 (98%) returning a search score of ≥80%. Direct comparisons of fibers before and after pressing show that the highest individual search score, and average search score from multiple single-point measurements, is overwhelmingly higher following our method. Our method immobilizes and improves the surface of the fiber, by creating a wider and uniform area for measurements. For FT-IR operators, this saves considerable time, improves reliability of the analysis, and, importantly, provides reproducibility of the spectra generated.

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