Feasibility Study on Quantification of Biodegradable Polyester Microplastics Based on Intrinsic Fluorescence

TL;DR

This study explores a new method to measure biodegradable microplastics using their natural fluorescence, offering a simpler and faster alternative to traditional labeling methods.

Contribution

The study introduces a label-free quantification method for biodegradable polyester microplastics using intrinsic fluorescence.

Findings

Biodegradable microplastics exhibit characteristic fluorescence emissions from molecular functional groups and conjugated group chromophores.

Fluorescence intensity correlates with microplastic size, shape, and concentration, enabling linear models with R2 values up to 0.963.

The intrinsic fluorescence method offers operational simplicity for rapid quantification of purified microplastics.

Abstract

While biodegradable plastics alleviate plastic pollution, their degradation-derived biodegradable microplastics (BMPs) pose new ecological risks, necessitating efficient quantification methods. This study explores a label-free approach by leveraging the intrinsic fluorescence of common biodegradable polyesters (PLA, PHB, PBS, PBAT, PCL). We find that biodegradable microplastics exhibit two types of characteristic fluorescence emission: one originating from molecular functional groups and the other originating from the chromophore formed by the aggregation of conjugated groups. Using PBAT as a model, we confirm that fluorescence intensity depends on the BMPs’ size and shape. Under 380 nm excitation, concentration-dependent signals are observed at 436 nm (indirectly from PBAT-enhanced water Raman scattering) and 465 nm (directly from PBAT intrinsic fluorescence), leading to successful linear models between BMPs’ mass concentration and fluorescence intensity over 100–500 mg/L, with correlation coefficients (R2) of 0.877 and 0.963, respectively. Compared with the fluorescence labeling method, the intrinsic fluorescence approach achieves comparable R2 while exhibiting lower signal intensity (~103). Nevertheless, its operational simplicity offers a distinct advantage for the rapid quantification of pre-isolated and purified microplastics.

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