# 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.

## Key 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.