Scientists at the Helmholtz-Zentrum Hereon validate and apply a newly developed analysis method for plastic particles and fibers
Screenshot hereon.de
They may be tiny, but they pose a global problem for humans and the environment: microplastic particles. These are plastic particles with a diameter between one micron and five millimeters. Their accurate analysis is an enormous challenge due to high error rates and the high time demand of previous methods. The considerably improved analysis of microplastics was carried out using a new method, Laser Direct Infrared (LDIR) Chemical Imaging. It was combined with a new sample preparation protocol that decomposes interfering components of the sample with fewer work steps by chemical and enzymatic reactions. The protocol was developed in the Department of Inorganic Environmental Chemistry. The chemical characterization of the microplastic particles is based on their absorption of infrared light.
Dr. Lars Hildebrandt, one of the two first authors, explains: “In this study, the device, which uses a so-called quantum cascade laser, demonstrated its advantages in the analysis of microplastic particles in environmental samples. It is fast and automatable, which is important for a future standard procedure.“ (Source: Hereon Press Release)
Read the complete Hereon Press Release:
==> Microplastics in the Indian Ocean
Hildebrandt, L., El Gareb, F., Zimmermann, T., Klein, O., Kerstan, A., Emeis, K.-C., & Pröfrock, D. (2022): Spatial distribution of microplastics in the tropical Indian Ocean based on laser direct infrared imaging and microwave-assisted matrix digestion. Environmental Pollution, Volume 307, 119547, doi:10.1016/j.envpol.2022.119547
Abstract:
Suspended particulate matter was collected from subsurface (6 m) water along an E-W transect through the tropical Indian Ocean using a specialized inert (plastic free) fractionated filtration system. The samples were subjected to a new microwave-assisted “one-pot” matrix removal (efficiency: 94.3% ± 0.3% (1 SD, n = 3)) and microplastic extraction protocol (recovery: 95% ± 4%). The protocol enables a contamination-minimized digestion and requires only four filtration steps. In comparison, classical sample processing approaches involve up to eight filtration steps until the final analysis. Microplastics were identified and physically characterized by means of a novel quantum cascade laser-based imaging routine.
LDIR imaging facilitates the analysis of up to 1000 particles/fibers (<300 μm) within approximately 1–2 h. In comparison to FTIR and Raman imaging, it can help to circumvent uncertainties, e. g. from subsampling strategies due to long analysis and post-processing times of large datasets. Over 97% of all particles were correctly identified by the automated routine – without spectral reassignments. Moreover, 100% agreement was obtained between ATR-FTIR and LDIR-based analysis regarding particles and fibers >300 μm.
The mean microplastic concentration of the analyzed samples was 50 ± 30 particles/fibers m−3 (1 SD, n = 21). Number concentrations ranged from 8 to 132 particles/fibers m−3 (20–300 μm). The most abundant polymer clusters were acrylates/polyurethane/varnish (49%), polyethylene terephthalate (26%), polypropylene (8%), polyethylene (4%) and ethylene-vinyl acetate (4%). 96% of the microplastic particles had a diameter <100 μm. Though inter-study comparison is difficult, the investigated area exhibits a high contamination with particulate plastics compared to other open ocean regions. A distinct spatial trend was observed with an increasing share of the size class 20–50 μm from east to west.