Microplastics detection in seawater using 2D Raman mapping of a filter (membrane) with residue

Nowadays, microplastics (MPs) – synthetic particles less than 5 mm in size – are widely present in the environment, and seen as a potential global threat to biodiversity, food safety and public health [1]. The problem is especially acute for seawater, since it is one of the main sources of foodstuff, and, at the same time, it accumulates a huge amount of plastic waste. As a result, MPs have already been found in the tissues and organs of many marine species, as well as in sea salt. To control and correct the situation, it is necessary the systematic extensive monitoring of MPs in seawater is including their type/size distribution, spreading over the water area/depth, weathering, degradation, interaction with chemical pollutants etc.

Raman spectroscopy is an effective analytical technique for this task [1, 2]. It is a rapid, non-contact and non-destructive method that uses monochromatic light to excite molecules in a material, and the spectrum of inelastically scattered light (Raman spectrum) to recognize the types of these molecules, intra- and intermolecular bonds. The method has high selectivity and sensitivity, allowing to identify different types of MPs, even if their number are low, they are mixed, or the irrelevant (matrix) components are present. In addition, one can observe minor changes in the MPs chemical composition and structure. Combination with scanning optical microscopy (Raman microscopy) yields the distribution of locally measured Raman spectra over the sample (hyperspectral imaging) that in turn can be used for simultaneous visualization of the MPs chemical composition, geometry and spatial distribution (chemical imaging).