## 3 Experimental Results and Validation
### Adulteration Detection  
After characterization of pure oil, the sensor was validated to detect adulteration in edible oil. For this purpose, pure olive oil was adulterated with castor, argemone, and mustard oil [34]. First of all, as illustrated in Figure 5, 1.5 mL mustard oil was mixed into 15 mL of olive oil, and from this solution, a 1 mL sample was placed directly on the sensor. The resonance frequency shifted from 5.25 GHz to 4.92 GHz. After that, 3 mL of mustard oil was mixed with 15 mL of olive oil, and a 1 mL sample from this solution was placed on the sensor, and the response was measured. In this case, the frequency shifted to 4.86 GHz. The same process was repeated for 4.5 mL of mustard oil in 15 mL olive oil. This time the frequency shifted to 4.69 GHz. Next, samples with 1.5 mL, 3 mL and 4.5 mL of castor oil, in 15 mL of olive oil, were tested. As shown in Figure 5, the frequency shifted to 4.88 GHz, 4.78 GHz and 4.68 GHz, for 1.5 mL, 3 mL and 4.5 mL samples, respectively. Finally, 1.5 mL, 3 mL and 4.5 mL of argemone oil were mixed with samples of 15 mL of olive oil, and the samples from the solutions were tested. Figure 5c shows the S\({}_{21}\) results for argemone oil as an adulterant. A shift in resonance frequency was clearly visible. Table 4 summarizes the shift in resonance frequency for adulteration detection in different samples of olive oil. The sensor not only detected adulteration, but also differentiated between different levels of adulteration, as seen in Table 4.  
\begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**OUT**} & **Q-Factor** & **Sensitivity** \\ \cline{2-3}  & **Q** & **S (\%)** \\ \hline Castor oil & 39.28 & 1.9 \\ Mustard oil & 37.61 & 2.1 \\ Olive oil & 28.12 & 3.2 \\ Flaxseed oil & 25.15 & 4.6 \\ Air & - & - \\ \hline \hline \end{tabular}
\end{table}
Table 3: Sensitivity and quality factor.  
Table 5 shows the comparative analysis of the proposed sensor with other state-of-the-art RF sensors previously reported in the literature. It is evident that our proposed sensor offers better sensitivity, as well as a better quality factor, on a low-cost substrate, thus, making it a suitable choice for practical applications.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample** & **Adulteration in Percentage** & **Resonance Frequency** & **Shift in Frequency** \\ \hline
1.5 mL mustard oil contamination & 10\% & 4.92 GHz & 290 MHz \\
3 mL mustard oil contamination & 20\% & 4.86 GHz & 350 MHz \\
4.5 mL mustard oil contamination & 30\% & 4.69 GHz & 520 MHz \\
1.5 mL castor oil contamination & 10\% & 4.88 GHz & 330 MHz \\
3 mL castor oil contamination & 20\% & 4.78 GHz & 430 MHz \\
4.5 mL castor oil contamination & 30\% & 4.68 GHz & 530 MHz \\
1.5 mL argemone oil contamination & 10\% & 4.80 GHz & 400 MHz \\
3 mL argemone oil contamination & 20\% & 4.78 GHz & 430 MHz \\
4.5 mL argemone oil contamination & 30\% & 4.61 GHz & 600 MHz \\ \hline \hline \end{tabular}
\end{table}
Table 4: Shift in resonance frequency compared with pure olive oil in different samples.  
Figure 5: Result of S\({}_{21}\) after adulteration of mustard oil in olive oil. (**a**) Result of S\({}_{21}\) after adulteration of mustard oil in olive oil. (**b**) Result of S\({}_{21}\) after adulteration of castor oil in olive oil. (**c**) Result of S\({}_{21}\) after adulteration of mustard oil in olive oil. (**d**) Resonant frequency at different values of adulteration.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Work** & **Sensitivity** & **Quality Factor** & **Structure** & **Frequency (GHz)** & **Sensing Area (mm\({}^{2}\))** \\ \hline
[33] & 0.27 & N/A & MTM & 2.5 & 280 \\
[29] & 0.05 & 20 & SRR & 2.53 & 124 \\
[37] & 0.35 & 24 & Resonator & 5.5 & 344 \\
**Our Work** & 4.6 & 39 & CSRR & 5.25 & 220 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Comparison of proposed sensor and other sensor.