Advances in microplastic characterization: Spectroscopic techniques and heavy metal adsorption insights

Microplastics (MPs) have become a matter of very serious concern as environmental pollutants nowadays because of the humongous increased production, use-and-discard nature associated with them, and the contamination of the environment with micro- and nano-plastics and other pollutants carried over by them, like many heavy metals, organic species, etc. Researchers have employed various techniques for detecting and classifying microplastics, mainly based on their optical or mass spectra or specific mass. This article discusses the various techniques used to characterize microplastics and surface-adsorbed heavy metals. Conventional techniques like Fourier Transform Infrared (FTIR) spectroscopy and Raman spectroscopy are widely used to identify the class of MPs and provide details about the extent of pollution. Heavy metals are one of the other environmental contaminants that can cause severe health issues. The microplastics act as a vector for transporting heavy metals from different locations and induce a potentiating effect. To identify the heavy metals adsorbed onto the MPs, various techniques such as Inductively Coupled Plasma Mass Spectrometry (ICP-MS), Energy Dispersive X-ray Spectroscopy (SEM-EDS), and others are used. After a review of the current identification approaches, which require the utilization of multiple resources and expertise for microplastic characterization and their surface-adsorbed heavy metal detection, the recent development of a single multi-modal spectroscopy system, capable of identifying both molecular and elemental information, which serve the purpose of microplastics and surface-adsorbed heavy metal identification in short times, enabling rapid screening and classification of samples, is discussed. Novel methods using such multi-modal systems-containing Laser-Induced Breakdown Spectroscopy (LIBS)/and Raman/fluorescence spectroscopy-under a single platform will come in handy in the future for the complete analysis of the microplastic samples for plastic classification and heavy metal detection.