How Critical is Spectral Range to Identification of Microplastics?

Analyzing Microplastics in the Environment
Oral Presentation

Presented by L. Tisinger
Prepared by W. Alwan 1, L. Tisinger2
1 - Agilent Technologies, 679 Springvale Road, Mulgrave, Victoria, 3170, Australia
2 - Agilent Technologies, 201 Hansen Ct, Suite 108, Wood Dale, IL, 60191, US


Contact Information: [email protected]; 61 3 9566 1041

ABSTRACT

Microplastic contamination is an emerging threat to environmental and ecological systems across the globe. Studies have shown that plastic particles cause harm to multiple types of organisms; they can be vectors to various other pollutants. Furthermore, research has shown that they can be present inside human tissue. The full extent of the impact of microplastics remains unclear, due to challenges in developing reliable methods for characterizing them.
Infrared (IR) spectroscopy is an established technique for characterizing polymers and microplastics. It identifies the molecular structure of materials by measuring the absorption of IR radiation. The resulting absorption bands, which are due to intramolecular vibrational modes, help identify organic or mineral materials through comparison of spectra with a library of spectra from known polymers. IR spectral acquisition is typically performed between 750 and 4,000 cm−1; however, only specific regions are used for the identification of microplastics. Spectral ranges are selected based on exclusion of regions with a low signal-to-noise ratio (S/N), substrate or filter limitations, or instrument manufacturer specifications. This study investigated the impact of narrowing the IR spectral range on the identification of microplastics, using (i) three different IR microscopic techniques: FTIR-ATR, µFTIR-FPA, LDIR and (ii) multiple spectral ranges. In each case, the major types of polymers were successfully identified when the spectral range was narrowed to the fingerprint region (975 to 1,800 cm−1). Because this is the spectral range used by the LDIR, this study establishes it as a reliable technique for the characterization of microplastics.