## 6 Methods of Microplastics Analysis  
### Visual Inspection Methods  
Visual inspection techniques of MPs include, observations made by the direct visual method with the naked eye, using an optical microscope, and/or electron microscope, which are used to select, classify MPs, and observe the colour and size of the tested object [122, 123] (Figure 4). These techniques are time-consuming and of low accuracy [124], in addition, the error rate is negatively related to the particle size [125].  
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline \multicolumn{1}{c}{**Characteristics of Tested Particles**} & \multicolumn{1}{c}{**Particle Size**} & \multicolumn{1}{c}{**Target Cells**} & \multicolumn{1}{c}{**Effect of MPs and/orNPs on Organisms**} & \multicolumn{1}{c}{**Ref.**} \\ \hline PET NPs & \(\sim\)62 nm & Human primary nasal epithelial cells & \(\bullet\) & Increased intracellular ROS. & \\ PET NPs & \(\sim\)62 nm & Human primary nasal epithelial cells & \(\bullet\) & Deprugulation of LC3-II and p62 expression. & [115] \\  & Beads: 10, 50 and 100 \(\mu\)m; Fragments: 25–75 and 75–200 \(\mu\)m & Peripheral blood mononuclear cells & \(\bullet\) & Beads induced immune response and cell hemolysis. & \\  & & & mononuclear cells & \(\bullet\) & Fragments caused cytotoxicity, inflammatory response, cell hemolysis, and produced ROS. & [116] \\ PS, PMMA, and PVC NPs & 50–310 nm & Human monocytes and 1000 cells. & Higher release of cytokines. & [117] \\  & & & cells. & & \\  & & & & \\ PS NPs. & 50 nm & Human peripheral blood lymphocytes & \(\bullet\) & Chromosomal damage. & \\  & & & & \(\bullet\) & Cytotoxic. \\  & & & & & \\  & & & & & \\  & & & & & \\ PS NPs and functionalized PS pristine, PS-COOH, PS-NH2 & 100 nm & Mouse mononuclear macrophage (RAW264.7) cell line & \(\bullet\) & High cytotoxicity. & \\  & & & & & \\  & & & & & \\  & & & & & \\  & & & & & \\  & & & & & \\  & & & & & \\  & & & & & \\ PS NPs & 100 nm, 600 nm & Human gingival fibroblasts & \(\bullet\) & Increased inflammatory markers expression NF-kB, MyD88 and NLR93. & [120] \\  & & & & & \\  & & & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\ PSMPs & 5–25, 25–75, 75–200 \(\mu\)m & Human dermal fibroblast, HeLa cell line, peripheral blood mononuclear cells (PBBMCs) and KATO III cells & \(\bullet\) & ROS generation. & \\  & & & & & \\ \hline \hline \end{tabular} Note(s): Microplastics (MPs), nanoplastics (NPs), Polystyrene (PS), polyethylene (PE), polypropylene (PP), polyethylene (PET), polyvinylene terephthalate (PET), polyvinylchloride (PVC), polychlorinated biphenyls (PCBs), polymethyl methacrylate (PMMA).  
\end{table}
Table 1: _Cont._  
Figure 4: Classification of visual inspection methods.  
The advantages of visual inspection method are easy to identify samples that include a significant amount of large MPs, giving a quick and affordable overall picture of their abundance. While the limitations are the samples' nature cannot be established, and the identification techniques must be combined.  
MPs < 100 \(\upmu\)m are difficult to identify or observe, even with a microscope [126; 127; 128]. Therefore, the development of technologies for the identification of MPs are crucial to attain more precise and effective results.