# Microplastic Pollution: Chemical Characterization and Impact on Wildlife
## 2 The Chemical and Physical Characterization of Microplastics
### A Summary of Techniques Available for Microplastic Analysis  
It is clear no perfect technique exists for MP analysis which can provide both comprehensive chemical identification and high-resolution imaging capability. Nonetheless, certain tools have been adapted for the workflow, and it is desirable to understand the advantages and limitations of each tool. Table 1 summarizes the main advantages and limitations of common tools used for the analysis of microplastics.  
In general, optical microscopy is a great first option to visualize suspected MPs. Then, FTIR or Raman can be used to collect data which verifies molecular composition. We note that SEM with EDX is particularly valuable when suspect MPs are chloro- or fluoropolymers such as PVC or Teflon. Chlorine or fluorine will produce a distinct elemental signature in  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Method** & **Advantages** & **Limits** \\ \hline Scanning Electron Microscopy (SEM) & & \\ \hline At the sample surface, a powerful electron beam is scanned. An electron beam’s scattering from the sample allows the images to be created. & This technique provides a high-resolution image of the sample (0.5 nm resolution). & The samples must be prepared for observation; type of polymer cannot be identified; high cost of instrument acquisition; tedious analysis \\ \hline Raman Spectroscopy & & \\ \hline The target is exposed to laser radiation and inelastic scattering occurs. The chemical makeup of samples may be determined using the frequency shift between two beams. & Reliable method for identifying microplastics; can & The sample must be properly prepared to isolate MPs of interest; Raman spectroscopy can be affected by additives, dyes, or impurities, sample \\ \hline Fourier-transform infrared spectroscopy (FTIR) & & \\ \hline Infrared light is used to illuminate samples, and absorbance or transmission spectra are then compared to those of known samples in libraries. & Dependable; nondestructive; micro-FTIR can study particles down to 20 \(\upmu\)m in size; & When the target particles are smaller than 20 \(\upmu\)m, the accuracy will decrease; expensive equipment; samples need to be pretreated/purified to remove matrix interferometers; detection spatial resolution limited by wavelength of radiation to tens of microns at best; water cannot be present \\ \hline Optical microscope & & \\ \hline Sample prepared and identified directly under the optical microscope & Rapid screening possible; lowest cost; ability to detect the size, shape, and color of MPs; easy to identify nonplastic particles when recognized & Lack of qualitative chemical identification; the potential to mistake polymer for inorganic materials; optical microscope may miss tiny particles. \\ \hline \hline \end{tabular}
\end{table}
Table 1: Comparison of techniques for microplastics analysis.  
the EDX spectrum which can be used for identification of fluoropolymers. While no single instrumental tool presently available can enable comprehensive analysis of MPs, the use of conventional methods in conjunction offers the analyst a viable toolbox. Further research is needed to delineate and improve upon methods for sample preparation and digestions, which is a crucial part of the MP analysis workflow.