Microplastics analysis in environmental samples – recent pyrolysis-gas chromatography-mass spectrometry method improvements to increase the reliability of mass-related data

Abstract

Thermal methods are of increased relevance in the field of mass-related microplastics (MP) analysis on trace level.

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

“…However, the lower the amount to be weighed, the higher the relative weighing error becomes and the more challenging it is to obtain a homogeneous mixture. So far, this has been one of the major drawbacks of Py-GC/MS (Fischer and Scholz-Böttcher, 2019). When combining Py-GC/MS with prior dissolution of polymers in an appropriate solvent such as TCB, stock solutions can be easily handled, quantitatively diluted or preconcentrated, and transferred directly into the pyrolyzer quartz tubes.…”

“…Since those internal standards are not polymers, they probably behave differently than the polymer analytes when heated to typical pyrolysis temperatures of 600-800 • C. Particularly polycyclic aromatic hydrocarbons such as anthracene are thermally stable and more likely to evaporate instead of thermally decomposing along with the polymer analytes. Accordingly, Fischer and Scholz-Böttcher (2019) reported that the deuterated anthracene might have interacted with the inner surface of the pyrolyzer which eventually decreased repeatability. Though expensive, deuterated plastics (Dierkes et al, 2019) or specialized polymers like poly(3,4-ethylenedioxythiophene) typically used in semiconductor industry could be promising alternatives since they decompose in the same temperature range as the polymer analytes (Jin et al, 2013).…”

“…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.…”

Critical Review of Processing and Classification Techniques for Images and Spectra in Microplastic Research

“…It is worth mentioning that out of the 15 studies using Py-GC-MS for microplastic analysis, 11 used an in-house library or pyrograms from reference/standard polymers. 23,65,83,[118][119][120][121][122][123]126,128 The multitier confirmation approach using pyrogram and mass spectra provides higher confidence in the data quality. One distinct advantage of Py-GC-MS over the spectroscopic methods is that there is negligible effect of shape, density, surface topology, color, brightness, or opacity on the quality of the chemical match.…”

Microplastics Detection Using Pyrolysis-GC/MS-Based Methods

“…As mentioned by Tsuge et al (2011), there are different types of PUR. Only two studies, Fries et al (2013) and Fischer and Scholz-Böttcher (2019), respectively, studied unspecified PUR type at 700 C and methylene diphenyl diisocyanate polyurethane (MDI-PUR) at 590 C. The obtained compounds are different between the two studies; it is first due to the difference of temperature but also because of the use of TMAH in the study at 590 C. No marker has been proposed by the authors. More information concerning all the compounds obtained after the pyrolysis of PUR are given in Table 3.…”