Effects of Chemical Digestion on Polyethylene and Polypropylene Microplastics: Implications for Reliable Food Analysis

Abstract

The presence of microplastics (MPs) in food products has become a concern, underscoring the need for reliable methods of isolation and analysis. There is no specific regulatory framework for monitoring MPs in food. A challenge is the lack of standardized and validated methods for the isolation and determination of MPs in food matrices. This study aimed to evaluate the effects of chemical digestion conditions used to isolate MPs from food matrices on the stability of polyethylene (PE) and polypropylene (PP) particles. The effects were evaluated using nitric acid, hydrochloric acid, hydrogen peroxide, potassium hydroxide, ethanol, and Milli-Q water at selected temperatures and reagent concentrations. Changes in particle surface morphology were assessed by scanning electron microscopy (SEM), while spectroscopic alterations were evaluated by Fourier transform infrared microspectroscopy (µ-FTIR). The SEM and µ-FTIR findings suggested that PE MPs were less affected than PP MPs under the tested treatment conditions. Less intensive treatment combinations were generally associated with fewer morphological and spectroscopic alterations for both polymers. The results showed that heating in Milli-Q water and treatment with acidic, oxidative, and alkaline reagents were associated with changes in selected recovery and spectroscopic parameters of PE and PP MPs under the tested experimental conditions.