## 3 Results and Discussion
### Performance on Real Samples  
The HPLC record of a real sample of olive leaves aqueous extract is reported in Figure 7a. The natural matrix delivers a complex chromatogram, where the peaks corresponding to TY, HT and OL were identified at 5.2 min, 3.8 min and 17.1 min respectively, thanks to the addition of standards. Their concentrations have been evaluated by HPLC using calibration curves, and in this typical sample, a 2.0, 4.5 and 633 uM concentrations of TY, HT and OL were found respectively.  
Figure 6: (**a**) fluorescence emission of MIPs 13-TY and 13-HT upon increasing concentrations of TY, HT and OL. (**b**) emission spectra of MIP 13-TY along the titration with TY.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**13-TY**} & \multicolumn{4}{c}{**13-HT**} \\ \cline{2-7}  & **LOD \({}^{\star}\), pM** & **LOD \({}^{\star}\), pM** & **Precision \({}^{\star}\), \%** & **LOD \({}^{\star}\), pM** & **LOD \({}^{\star}\), pM** & **Precision \({}^{\star}\), \%** \\ \hline TY & 0.1 & 0.2 & 2.64 & 0.5 & 5.4 & 4.05 \\ HT & 0.5 & 1.2 & 4.35 & 0.5 & 1.3 & 3.06 \\ OL & 0.9 & 2.1 & 3.12 & 0.7 & 10.2 & 8.92 \\ \hline \hline \end{tabular}  
* * limit of detection evaluated with the 3\(\sigma\) method after linear regression of emission data vs. log of ligand concentrations in the 10 M–10 nM range; b: limit of quantification set at 10\(\sigma\) over the starting signal with no ligands; c: average % error over the whole set of standard deviations of the emission signals from triplicate measures at each concentration.  
\end{table}
Table 3: Sensitivity and precision of MIP fluorescence titrations.  
The rebinding ability of our MIPs was therefore evaluated on the extract. The amount of MIPs 13-TY and 13-HT to be added to the samples was defined according to its ability to capture OL (Table 2), as this is the main compound in the extract. We have found that the polymers at 6 mg/mL, in a 1:1 dilution of the extract, are able to remove more than 70% of OL with a very rapid process during the first two hours (Figure 7b). The possibility of measuring the concentration of phenols on the real samples was finally evaluated with MIP 13-TY as its calibration curve performs at best, on a sample containing 398 uM OL. This concentration is well over the upper limit of the dynamic range of our system. This fact allows us to highly dilute the sample minimizing the matrix effect. The sample was, in fact, added at a final 1:10\({}^{5}\) dilution to a 2.5 mg/mL solution of MIP 13-TY. Under this dilution the pH is 6.6 as in the water solution of MIP, and the system behaves as shown before in water. The increase of fluorescence was recorded. The datum from a triplicate measure was used to evaluate the total concentration of phenols expressed as OL, and to this end, a calibration curve was used from a linear regression of the fluorescence titration data in the 1 pM-100 nM range (Figure 7c). By this way, the calculated phenol concentration in the real sample turned out to be \(433\pm 20\) uM. This result is in line with that obtained in the reference HPLC method.  
Figure 7: (**a**) HPLC analysis of olive leaves extracts, (**b**) capture of OL from olive leaf extracts after addition of MIPs, (**c**) calibration curve of fluorescence enhancement after addition of OL to MIP 13-TY (r\({}^{2}\) = 0.991, intercept 1.796 \(\pm\) 0.067, slope 0.1461 \(\pm\) 0.0069).