Critical assessment of approach towards estimation of microplastics in environmental matrices

Microplastics (MPs) are the contaminants of growing concern due to their persistent properties in the environment. This review compares the global data on MPs concentration in soil, sediment, salt, sand, biosolids, and water. Previous studies have also developed various methods to estimate MPs for different environmental matrices, which were generally based on salt-based density separation, physical (microscopy), chemical characterization (spectroscopy), and visual counting for extraction, identification, and quantification, respectively. In most of the existing field-based studies, MPs are usually identified and detected by microscopic observation and Fourier transform infrared (FTIR) analysis, which maximize the probability of error in the estimation process. A combination of thermogravimetric analysis-FTIR spectroscopy, Raman microspectroscopy, optical photothermal infrared, and pyrolysis/gas chromatography-mass spectrometry are used for the identification, recognition, and quantification of MPs in the heterogeneous solid and liquid matrices for minimizing the interference and misinterpretation of the other constituents (organic matter) present in the samples, especially soil, sediments, and biosolids.

Automated summary

This review compares the global data on microplastics (MPs) concentration in various environmental matrices and discusses the methods used for their estimation and identification. Previous studies have mainly relied on microscopic observation and Fourier transform infrared (FTIR) analysis, which may introduce errors in the estimation process. Newer techniques such as thermogravimetric analysis-FTIR spectroscopy, Raman microspectroscopy, optical photothermal infrared, and pyrolysis/gas chromatography-mass spectrometry are being used to improve the accuracy of MPs identification and quantification.