Focal plane array detector-based micro-Fourier-transform infrared imaging for the analysis of microplastics in environmental samples

Martin Günter Joachim Löder; Mirco Kuczera; Svenja Mintenig; Claudia Lorenz; Gunnar Gerdts

doi:10.1071/EN14205

RESEARCH ARTICLE (Open Access)

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Focal plane array detector-based micro-Fourier-transform infrared imaging for the analysis of microplastics in environmental samples

Martin Günter Joachim Löder ^A ^B ^C , Mirco Kuczera ^A , Svenja Mintenig ^A , Claudia Lorenz ^A and Gunnar Gerdts ^A

+ Author Affiliations

- Author Affiliations

^A Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung, Biologische Anstalt Helgoland, POB 180, D-27483 Helgoland, Germany.

^B Animal Ecology I, University of Bayreuth, Universitätsstraße 30, D-95440 Bayreuth, Germany.

^C Corresponding author. Email: martin.loeder@uni-bayreuth.de

Environmental Chemistry 12(5) 563-581 https://doi.org/10.1071/EN14205
Submitted: 30 September 2014 Accepted: 5 February 2015 Published: 6 August 2015

Journal Compilation © CSIRO Publishing 2015 Open Access CC BY-NC-ND

Environmental context. Microplastics are of increasing environmental concern following reports that they occur worldwide from the arctic to the deep sea. However, a reliable methodology that facilitates an automated measurement of abundance and identity of microplastics is still lacking. We present an analytical protocol that applies focal plane array detector-based infrared imaging of microplastics enriched on membrane filters applicable to investigations of microplastic pollution of the environment.

Abstract. The pollution of the environment with microplastics (plastic pieces <5 mm) is a problem of increasing concern. However, although this has been generally recognised by scientists and authorities, the analysis of microplastics is often done by visual inspection alone with potentially high error rates, especially for smaller particles. Methods that allow for a fast and reliable analysis of microplastics enriched on filters are lacking. Our study is the first to fill this gap by using focal plane array detector-based micro-Fourier-transform infrared imaging for analysis of microplastics from environmental samples. As a result of our iteratively optimised analytical approach (concerning filter material, measuring mode, measurement parameters and identification protocol), we were able to successfully measure the whole surface (>10-mm diameter) of filters with microplastics from marine plankton and sediment samples. The measurement with a high lateral resolution allowed for the detection of particles down to a size of 20 μm in only a fractional part of time needed for chemical mapping. The integration of three band regions facilitated the pre-selection of potential microplastics of the ten most important polymers. Subsequent to the imaging the review of the infrared spectra of the pre-selected potential microplastics was necessary for a verification of plastic polymer origin. The approach we present here is highly suitable to be implemented as a standard procedure for the analysis of small microplastics from environmental samples. However, a further automatisation with respect to measurement and subsequent particle identification would facilitate the even faster and fully automated analysis of microplastic samples.

Additional keywords: microplastic analysis, microplastic detection, microplastic identification.

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