The first application of quantitative 1 H NMR spectroscopy as a simple and fast method of identification and quantification of microplastic particles (PE, PET, and PS)

Abstract

Microplastic (0.001–5 mm) is a serious problem for the environment and is globally distributed. It has been detected in marine and limnic waters as well as in organisms. Until now, microplastic (MP) particles in environmental samples are mainly identified by Fourier transform infrared (FTIR) or Raman spectroscopy. Usually, for quantitative detection, time-consuming counting of MP particles in the sample is described. Therefore, a great need for research in the field of size-independent quantitative analysis of MP particles is evident. We present herein the application of quantitative ¹H NMR spectroscopy (qNMR) as a new method for the qualitative and quantitative analysis of MP in solution. Polyethylene (PE) granules with a size distribution of < 300 μm, polyethylene terephthalate (PET) fibers with a length of approx. 500 μm, and polystyrene (PS) beads with a size distribution of 0.5–1 mm were qualitatively and quantitatively analyzed as prototypical MP particles in model samples using a calibration curve method. As internal standard, the residual proton signal of the deuterated solvent was used. For all polymer types, linearity of the method is > 0.994 R², and the precision is in the range of 99.4–99.9%. The limit of detection (LOD) is in the range of 19–21 μg/mL and the limit of the quantification (LOQ) is in the range of 74–85 mg/mL, so the LOD and LOQ are observed in an environmentally relevant size. In this work, we therefore show that size-independent qualitative and quantitative determination of microplastic particles in model samples using qNMR is possible.

Graphical abstract

Working flow for the first application of qNMR as a simple and fast method of identification and quantification of microplastic (MP) particles (PE, PET, PS). 338 × 190 mm (96 × 96 DPI)

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