Quantitative Analysis of Poly(ethylene terephthalate) Microplastics in Soil via Thermogravimetry–Mass Spectrometry

Abstract

The use of plastic materials in daily life, industry, and agriculture can cause soil pollution with plastic fragments down to the micrometer scale, i.e., microplastics. Quantitative assessment of microplastics in soil has been limited so far. Until now, microplastic analyses in soil require laborious sample cleanup and are mostly restricted to qualitative assessments. In this study, we applied thermogravimetry-mass spectrometry (TGA-MS) to develop a method for the direct quantitative analysis of poly(ethylene terephthalate) (PET) without further sample pretreatment. For this, soil samples containing 1.61 ± 0.15 wt % organic matter were spiked with 0.23-4.59 wt % PET bottle recyclate microplastics. dl-Cysteine was used as the internal standard (IS). Sample mixtures were pyrolyzed with a 5 K min ramp (40-1000 °C), while sample mass loss and MS signal intensity of typical PET pyrolysis products were recorded. We found MS signal intensities linearly responding to microplastic concentrations. The most-promising results were obtained with the IS-corrected PET pyrolysis product vinylbenzene/benzoic acid ( m/ z = 105, adj. R = 0.987). The limits of detection and quantification were 0.07 and 1.72 wt % PET, respectively. Our results suggest that TGA-MS can be an easy and viable complement to existing methods such as pyrolysis or thermogravimetry-thermal desorption assays followed by gas chromatography/mass spectrometry detection or to spectral microscopy techniques.

Fundamental Insights into the Covalent Silane Functionalization of NiFe Layered Double Hydroxides

“…As previously stated in the literature, TG‐MS is a powerful technique that can be used to characterize both solid and liquid materials. Thanks to the careful monitorization of the mass sample and the analysis of the gases, which leave the material when heated, this technique allows gathering additional information on the sample composition based on its constituents . This technique focuses on the determination of the stability of the APTES molecules attached to the inorganic layers as well as the identification of the intercalated moieties within the LDH structure .…”

A simple method for the selective quantification of polyethylene, polypropylene, and polystyrene plastic debris in soil by pyrolysis-gas chromatography/mass spectrometry

“…For the recovery experiment, three soils with different textures and organic carbon (C org ) contents were selected (Table 1). RefeSol 06-A (Fraunhofer IME, Schmallenberg, Germany) and LUFA 2.2 (Landwirtschaftliche Untersuchungs-und Forschungsanstalt, Speyer, Germany) as previously used by David et al (2018) served as reference soils from organically managed arable areas. In addition, a pristine forest soil was taken from a continuous observation site of the Landesamt für Geologie und Bergbau in Wallmerod (WR), Rhineland-Palatinate, Germany (Meyer et al, 2018).…”

“…In such cases, thermoanalytical techniques such as thermogravimetry/mass spectrometry (David et al, 2018(David et al, , 2019, pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS; Scholz-Böttcher, 2017, 2019), or combinations of TGA with GC/MS namely thermal desorption-gas chromatography/mass spectrometry (TED-GC/MS; Dümichen et al, 2015;Duemichen et al, 2019) may demonstrate their inherent benefits. All these methods are based on thermal decomposition of polymer mixtures at temperatures >500 • C and their quantification via indicator pyrolysates.…”

“…All these methods are based on thermal decomposition of polymer mixtures at temperatures >500 • C and their quantification via indicator pyrolysates. Currently, instrumental detection limits range from 3 to 200 ng for PS (Fischer and Scholz-Böttcher, 2019;Duemichen et al, 2019) and up to 0.5-50 µg for PE, PP, and PET (Duemichen et al, 2019;David et al, 2018). In contrast to optical methods, thermoanalytical techniques are assumed to be more robust against impurities from sample matrix.…”

Microplastics in soils: assessment, analytics and risks

“…Samples may be randomly selected or, alternatively, chemical imaging using a focal array plan (FPA) may be implemented, thus allowing for the simultaneous analysis of multiple points (Renner et al 2018). Literature surveys suggest that microscopic variations of both Raman and FTIR (mRaman and mFTIR) spectroscopies have steadily become dominant in the identification of MPs (Fuller and Gautam 2016;David et al 2018;Corradini et al 2019); however, these methodological approaches will have to deal with an increasing number of samples, and, likely, with an increasing number of particles per sample, of which all spectra should be obtained, recorded and analysed (Renner et al 2018).…”