# Microplastics in Water Resources: Threats and Challenges
## 5 Methods for Determining Microl plastics
### FT IR and RS  
Fourier transform infrared (FTIR) spectroscopy is a widely used chemical analysis method that is widely applied in the identification and characterization of microplastics. To apply this technique to microplastics analysis, proper sample preparation is essential [129]. The cleaning and extraction processes for the samples do not differ significantly from procedures used in other analytical methods and include chemical digestion, density separation, filtration, etc. [130]. Subsequently, microplastics are placed on an appropriate slide in a thin layer or in a KBr pellet to obtain a clear IR spectrum [131]. The FTIR spectrometer emits infrared radiation at various wavelengths, which passes through the sample. The microplastic molecules absorb radiation at frequencies characteristic of their chemical bonds, causing changes in the FTIR spectrum. The transmitted radiation passes through an interferometer, and the resulting spectrum is recorded. The outcome is an FTIR spectrum that represents light absorption as a function of wavenumber (cm\({}^{-1}\)) [132]. Characteristic bands in the FTIR spectrum correspond to different chemical bonds in the plastic molecules. Analyzing these bands allows for the identification of the type of plastic and additional components, such as additives or contaminants. The obtained FTIR spectrum can be compared with a reference database of microplastic spectra, allowing precise identification of the plastic type [133]. FTIR also allows for the assessment of the presence of chemical additives in the sample, which is crucial to determining the environmental risk [134]. Using the FTIRmethod to study microplastics enables precise identification of the plastic type, which is key to understanding and monitoring the presence of microplastics in various environments. However, as with any method, FTIR has drawbacks. FTIR may encounter difficulties in analyzing microplastics present in complex mixtures, especially when other components, such as organic substances or mineral compounds, are present. In addition, other substances present in the sample, such as dyes, can introduce interference in the FTIR analysis, making it difficult to precisely determine the type of microplastic. Although characteristic bands are identified, FTIR may not always unequivocally determine the type of microplastic, especially when they are modified or contain additives [135,136]. Proper sample preparation is the key to obtaining accurate results. Improper sample preparation, such as improper distribution of microplastics on the backing, can lead to erroneous results [137]. Also, in the case of very small microplastic particles, FTIR may have difficulty detecting and identifying them [138]. In such cases, alternative techniques such as Raman spectroscopy can be more effective, particularly when analyzing small or fine microplastics. Raman spectroscopy analyses molecular vibrations through light scattering, detecting unique vibrational signatures specific to molecules. It is highly sensitive to nonpolar groups, less affected by water, and is effective for analyzing wet samples with minimal preparation. RS offers better spatial resolution than IR techniques, making it suitable for identifying small microplastics [139]. [PERSON] et al. (2018) noted that Raman spectroscopy naturally has better spatial resolution than IR-based techniques and is therefore the preferred method for identifying small microplastics (<20 \(\upmu\)m) [132]. Interesting insights regarding FTIR and Raman methods were provided by [PERSON] et al. in their study. They showed that Raman spectroscopy enables the identification of microplastic particles as small as 5 \(\upmu\)m, with the potential to detect particles down to 1 \(\upmu\)m, which is considered the lower size limit for microplastics. However, compared to FTIR imaging, Raman spectroscopy requires longer measurement times, which can be reduced at the cost of spectral quality and detection sensitivity.