Analytical methods for identifying microplastics in environment: a critical review

ABSTRACT The graphical abstract illustrates the process of microplastic analysis, including digestion, density separation, vacuum filtration, visual analysis, and spectroscopic analysis. Microplastics (MPs) are widespread environmental pollutants found in water, soil, air, and living organisms. This review aimed to represent the analytical methods for identifying MPs in the environment. The study considered available data from journals, books, and reports published within the last 22 years on the topic. Their analysis involves several key steps: sample collection, preparation, density separation, digestion, filtration, identification, and quantification. Common floating agents for density separation include NaCl, NaI, ZnCl2, and Na6[H2W12O40], with NaCl favored for its cost-effectiveness and low environmental impact. For organic matter digestion, 30% H2O2 is widely used, while 1 M NaOH is effective and safer for digesting fish tissues. Vacuum filtration using glass fiber or cellulose nitrate filters captures MPs, which are then analyzed under a stereomicroscope to assess color, shape, size, and abundance. Nile Red staining enhances visibility under fluorescence microscopy. Polymer identification is performed using Fourier transform infrared spectroscopy or Raman spectroscopy, with Raman being more sensitive to particles <10 μm. Scanning electron microscopy–energy dispersive X-ray spectroscopy helps analyze surface morphology and elemental composition. Standardizing MP analysis methods is crucial for ensuring consistent, comparable data across global studies.