# A Portable Optical Sensor for Microplastic Detection: Development and Calibration
## 3 Results and Discussion
### Comparison with Conventional Techniques  
We compared the performance of our sensor with that of conventional techniques, including FTIR spectroscopy, Raman spectroscopy, and UV-Vis spectroscopy. The Table 3 below highlights the key features of the standard microplastic detection methods alongside the developed sensor. FTIR and Raman spectroscopy offer high selectivity and precision in molecular identification, but they are expensive, require sample preparation, and are not portable. The developed sensor addresses these limitations, offering rapid analysis, minimal preparation, and field portability, making it an accessible tool for researchers conducting preliminary microplastic analysis.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Feature** & **FTIR Spectroscopy** & \multicolumn{1}{c}{**Raman Spectroscopy**} & \multicolumn{1}{c}{**Uv-Vis Spectroscopy**} & \multicolumn{1}{c}{**Developed Sensor**} \\ \hline
**Detection Mechanism** & Absorption of infrared light & Inelastic scattering of photons & Absorption of ultraviolet and visible light & Absorption of multiple wavelengths using LEDs and detection through DIP \\ \hline
**Sensitivity Rate** & Detects down to \(\sim\)20 \(\mu\)m; highly detailed molecular info & Detects as small as 1 morpho-chemical analysis & Detects changes in light absorption for MPs \(>\) 100 \(\mu\)m & Detects changes in light absorption for optimized for MPs \(>\) 100 \(\mu\)m \\ \hline
**Selectivity** & High, based on molecular vibrations & High, based on molecular vibration & Moderate, based on the electronic transition & Moderate, based on electronic transition and based on morphological characteristics \\ \hline
**Sample preparation** & Requires sample preparation [13] & Requires sample preparation [13] & Minimal sample preparation & Minimal sample preparation \\ \hline
**Measurement Duration** & Several minutes & Several minutes & Few minutes & 20 s per LED. And 2 min for image processing. \\ \hline
**Data Output** & Spectra & Spectra & Absorbance spectra &
\begin{tabular}{c} CSV file with \\ 2000 data values, \\ using absorbance as a function of voltage. \\ \end{tabular} \\ \hline
**Automation** & Partial & Partial & Partial \\ \hline
**Portability** & Limited & Limited & Moderate & High, optimized for field use with simple preparation protocols \\ \hline
**Cost** & High & High & Moderate to High & Low to mid-low \\ \hline
**Reproducibility** &
\begin{tabular}{c} High, but it depends \\ on the sample \\ preparation \\ \end{tabular} & High, but it depends on the sample preparation & Moderate to High & Moderate varies with environmental conditions. \\ \hline \hline \end{tabular}
\end{table}
Table 3: Comparison of the developed sensor with conventional techniques, including FTIR, Raman, and UV-Vis spectroscopy.  
The prototype achieves sensitivity comparable to that of UV-Vis spectroscopy, effectively identifying the presence of microplastics in controlled conditions. Unlike FTIR and Raman spectroscopy, which detect particles as small as 1 \(\upmu\)m and provide detailed morpho-chemical analysis (as highlighted in [PERSON] et al. and [PERSON] et al.), the prototype is designed for practical use and accessibility in different environments. It quickly detects potential microplastic contamination, allowing researchers to identify polluted samples without needing specialized laboratory equipment.  
This device combines functionality and simplicity. It combines optical sensing with mechanical and electronic precision to provide reliable results without the high cost or complexity of traditional methods. Moreover, its rapid detection capabilities help researchers process samples quickly and avoid unnecessary analysis. These strengths make the prototype a practical tool for addressing microplastic pollution in research and field work.