## 2 Results
### Optimization the Electrochemical Parameters  
Eleven different MIPs were synthesized with different amounts of activated TiO\({}_{2}\), MWCNT, Rhodamine B, functional monomer AM, and KH550 as summarized in Table 1. The resulting polymers showed distinct responses while applied as electrochemical film modifiers for SPCE in the detection of Rhodamine B. In fact, MIPs provided the best sensitivity (Figure 3). The parameters affecting the electrochemical detection of Rhodamine B were then optimized, starting with the electrode modification volume by testing 2, 4, 6, 8, and 10 \(\upmu\)L. The best results were achieved with 6 \(\upmu\)L. Several electrolyte solutions were then tested, namely, ammonium acetate, ammonium phosphate, HNO\({}_{3}\), KCl, NaOH, H\({}_{3}\)PO\({}_{4}\), and CH\({}_{3}\)COOH (0.1 M of each). The best detection was provided using 0.1 M of H\({}_{3}\)PO\({}_{4}\) (Figure 4). The effects of adjusting the pH value of the supporting electrolyte on the oxidative behavior of Rhodamine B disclose significant information about the mechanisms of the electrochemical reactions at the modified electrode. Therefore, the influences of pH and the supporting electrolyte on the electrooxidation of Rhodamine B were carefully investigated by linear sweep voltammetry. The suitable pH conditions were preliminarily studied using H\({}_{3}\)PO\({}_{4}\) at different pH values as representatives of acidic, neutral, and basic buffer electrolytes, respectively. The obtained  
Figure 2: Cyclic voltammograms of different electrodes: (**a**) MIP-SPCE, (**b**) NIP-SPCE, (**c**) MWCNT/TiO\({}_{2}\)-SPCE, and (**d**) non-modified SPCE at 10 mg L\({}^{-1}\) Rhodamine B in 1 M H\({}_{3}\)PO\({}_{4}\), at scan rate of 50 mV s\({}^{-1}\). voltammograms from the simultaneous detection are shown in Figure 4. With increasing pH value, the anodic currents of Rhodamine B decreased obviously. We believe that in our case, an acidic supporting electrolyte would strongly increase the current. By considering the pKa values of Rhodamine B, the results can be attributed to the fact that the ionic forms of the target analytes affect the electrooxidation processes at the electrode surface. These ionic forms in neutral and basic supporting electrolytes transfer almost no electrons at the electrode surface. From these results, it can be concluded that an acidic supporting electrolyte is suitable for the detection of Rhodamine B. Finally, the detected volume was studied in the range of 10-50 \(\mu\)L, concluding 40 \(\mu\)L as the ideal droplet volume. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Polymer**} & **TiO2 NPs** & **MWCNT** & **KH550 (mL)** & **AM (mg)** & **Rhodamine B (mg)** \\ \hline MIP1 & 2 & 5 & 4 & 1.4 & 2 \\ MIP2 & 7 & 5 & 4 & 1.4 & 2 \\ MIP3 & 20 & 5 & 4 & 1.4 & 2 \\ MIP4 & 7 & 10 & 4 & 1.4 & 2 \\ MIP5 & 7 & 15 & 4 & 1.4 & 2 \\ MIP6 & 7 & 5 & 10 & 1.4 & 2 \\ MIP7 & 7 & 5 & 1 & 1.4 & 2 \\ MIP8 & 7 & 5 & 4 & 5 & 2 \\ MIP9 & 7 & 5 & 4 & 10 & 2 \\ MIP10 & 7 & 5 & 4 & 1.4 & 5 \\ MIP11 & 7 & 5 & 4 & 1.4 & 10 \\ \hline \hline \end{tabular}  
* MIP: Molecular imprinted polymer, MWCNT: multiwalled carbon nanotube, AM: acrylamide, and KH550: (3-Aminopropyl) triethoxysilane.  
\end{table} 
Table 1: Composition of the polymerization mixtures used for the MIP synthesis. Figure 4: Analytical signals obtained for detection of Rhodamine B: (**A**) different supporting electrolytes, (**B**) different H\({}_{3}\)PO\({}_{4}\) concentrations, and (**C**) pH (1, 3, 5, 7, 9, and 11). Figure 3: Electrochemical response of 10 mg L\({}^{-1}\) Rhodamine B in 1 M H\({}_{3}\)PO\({}_{4}\) using 11 distinct MIPs as electrochemical film modifiers for SPCE. The influence of foreign compounds in the determination of Rhodamine B was investigated for various and specific interfering substances in the samples, including Rhodamine 123, Rhodamine 6G (5 times content), and ascorbic acid, citric acid, glucose, maltose, Mg+2, Cu+2, and Fe+2 (20 times content).