Microplastic Mass Quantification Using Focal Plane Array-Based Micro-Fourier-Transform Infrared Imaging

The quantification of microplastics (MPs) in environmental samples on a mass basis can be used to provide a more comprehensive understanding of the fate and transport of MPs in the environment. In this study, a precise method for quantifying the volumes and, by extension, the masses of MPs was developed. This novel approach is grounded in the principles of Beer’s law and makes use of focal plane array (FPA) micro-Fourier-transform infrared imaging. This methodology capitalizes on the absorption characteristics observed at each pixel within FPA imaging data, to identify variations in thickness across the x–y plane and facilitate a comprehensive characterization of the 3D geometries of MPs. This approach represents an advancement from previous assumptions that treated all MPs as regularly shaped and extrapolated thickness information solely based on x–y coordinates. Linear regression was used to model the relationship between absorbance and plastic thickness, drawing from data collected from plastic membranes with controlled thickness. The model was validated through a comparison between known and estimated volumes of MPs characterized by well-defined geometries, yielding errors <5%, substantiating the validity and accuracy of the proposed approach. The proposed method developed in this study holds the potential to emerge as a standard protocol for the accurate quantification of MP mass in environmental samples.