Methodological approach based on LIBS imaging for the identification of microplastics in the environment. A case study for water samples

The present article reports the detection and identification of microplastics (MPs) by constructing LIBS images from the emission lines of different markers. Given the increasing environmental concern regarding the presence of microplastics (MPs), the development of robust and sensitive analytical methodologies for their detection has become imperative. The characterization of the different types of MPs found in the environment is a key aspect when studying the pollution produced by these particles. However, the working protocols for evaluating this pollution include complex sample treatments or coupled techniques that increase the costs of these analyses. For this reason, the present work proposes a protocol for studying MPs that involves a novel, simple, and rapid sample preparation method, combined with a single LIBS image scan, which enables the construction of the particle distribution in the filter for the detection and classification of MPs. In this work, four different plastics were crushed, suspended in water, and filtered, emulating what could be found in a real sample. These plastics had specific markers, allowing for the use of a combination of spectral normalization and wavelength isolation related to a specific plastic to differentiate MPs in a mixture sample selectively. This approach could be applied to assess MP pollution in real samples when working on a larger scale or with more complex samples. In this way, a quick, inexpensive, and straightforward method was developed to detect and classify four types of MPs, which applied to both simple and more complex samples. • A simple preparation protocol allowed the isolation of microplastics in water samples. • A single LIBS scan allows for the obtention of images for detecting microplastics. • Different elements act as markers for each plastic. • Elemental distribution according to each microplastic type is obtained. • A quick, cheap and simple detection and differing of microplastics is achieved.