A review on microplastics: sources, environmental fate, degradation pathways, and analytical identification methods

Microplastics pose a serious threat to ecosystems, making their detection and characterization a critical area of scientific research. This review provides a comprehensive overview of the current techniques employed for investigating the contamination, sources, environmental distribution, toxicological impacts, and biodegradation processes of microplastics within complex environmental matrices. A range of analytical methods is discussed, including visual inspection, microscopy techniques, and advanced spectroscopic methods such as Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, surface-enhanced Raman spectroscopy (SERS), and quadrupole mass spectrometry (MS) coupled with pyrolysis gas chromatography. Additional approaches such as staining methods, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and near-infrared (NIR) spectroscopy are also evaluated. Special emphasis is placed on the emerging potential of electrochemical sensing technologies as low-cost, efficient instruments for identifying and classifying microplastics. Despite the growing interest in the electrochemical remediation of microplastics, there is a notable gap in research focusing on electrochemical sensors for monitoring microplastics. The novel approach of this work is the systematic comparison and critical evaluation of various electrochemical sensing approaches for microplastic detection. This analysis is based on the most recent literature and examines their relative advantages, limitations, and suitability in comparison to conventional detection methods. Additionally, this review presents a thorough examination of strategies for the fabrication of electrochemical sensors, encompassing recognition elements, advanced immobilization techniques, and limit of detection protocols that are specifically designed for microplastic detection applications.