## 3 Results and Discussion
### Comparison of Interaction Parameters of PILs-Based Stationary Phases
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**T (\({}^{\circ}\)C)** & **PIL00** & **PIL10** & **PIL20** & **PIL30** & **PIL40** & **PIL60** \\ \hline
100 & 0.31 & 0.94 & 1.34 & 1.40 & 1.87 & 2.16 \\
150 & 0.26 & 0.91 & 1.32 & 1.37 & 1.79 & 2.10 \\
200 & 0.24 & 0.86 & 1.27 & 1.31 & 1.70 & 2.01 \\
230 & 0.29 \({}^{\mathrm{a}}\) & 0.80 & 1.20 & 1.25 & 1.58 & 1.84 \\
250 & b & 0.88 \({}^{\mathrm{a}}\) & 1.16 & 1.24 & 1.53 & 1.75 \\
280 & & & b & 1.24 \({}^{\mathrm{a}}\) & 1.19 & 1.46 & 1.62 \\
300 & & & & b & 1.23 \({}^{\mathrm{a}}\) & 1.52 \({}^{\mathrm{a}}\) & 1.59 \\
320 & & & & & b & b & 1.83n \({}^{\mathrm{a}}\) \\
340 & & & & & & & b \\ \hline \hline \end{tabular}  
* Peaks tailing was observed. \({}^{\mathrm{b}}\) No retention was observed for naphthalene.  
\end{table} 
Table 2: Variation in naphthalene retention factor using PIL columns with different mixtures of AAIL and DVB using the isothermal method. and for the commercial 1,9-di(3-vinylimidazolium) nonane bis(trifluoromethylsulfonyl)imide-based column displaying ditopic bisimidazolium units [23]. It is interesting to note that the value for this parameter (b-term) initially decreased with the crosslinking (for 10 and 20% DVB), which can be attributed to the limitation in mobility and accessibility of the acidic sites in the crosslinked polymeric matrix. However, for higher degrees of crosslinking (30 and 40%), the value of the b-term increased significantly at low temperatures (up to 0.90 at 60 \({}^{\circ}\)C for 40% DVB). The partial generation of polymer domains with different polarities upon increasing the DVB content at those levels can be responsible for this phenomenon. At higher temperatures, the b-term always decreased with the crosslinking, as the increased chains mobility will reduce domain separation. In all cases, the value of this parameter decreased with temperature and, at 120 \({}^{\circ}\)C, fully inversely correlated with the DVB content, as could be expected. The e-term shows the ability of the PIL-silica composites to interact with solutes through \(\pi\)- and nonbonding electron interactions, being positive when the stationary phase interacts with the solutes through the electron lone pairs of the present heteroatoms and/or the \(\pi\)-cloud of the aromatic rings present. For all the columns studied, the e-term was very small or slightly negative, indicating that there is no appreciable interaction between the probe solutes and the stationary phases through \(\pi\)- or n-electrons. A value of zero has been calculated for this term in the case of BMIM derivatives not containing electron-donating substituents at the imidazolium ring nor strongly coordinating anions [54]. In the present case, this indicates that the aromatic rings of the polymeric matrix (from DVB units) do not significantly contribute to this kind of interaction. PIL20 containing 20% of DVB and  
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline
**PIL** & **T** & **c** & **e** & **s** & **a** & **b** & **1** & **R2** & **n** & **SE** & **F** \\ \hline \multirow{4}{*}{PIL00} & \multirow{4}{*}{60} & \(-4.10\) & \(-0.12\) & \(1.69\) & \(1.72\) & \(0.75\) & \(0.45\) & \multirow{4}{*}{0.98} & \multirow{4}{*}{23} & \multirow{4}{*}{0.06} & \multirow{4}{*}{192} \\  & & (0.09) & (0.12) & (0.11) & (0.19) & (0.14) & (0.03) & & & & \\  & & \(-3.89\) & \(0.00\) & \(1.55\) & \(1.34\) & \  
showing slightly positive values at 60 \({}^{\circ}\)C is the stationary phase displaying the lowest variation in this parameter with temperature, suggesting again a high degree of homogeneity in the polymers formed. In the case of the l-term, the stationary phases studied had l \(>\) 0 coefficients, implying that positive dispersion interactions dominate. As can be seen from the higher values obtained for the crosslinked stationary phases, the structural components originating by the polymerization of DVB provide a clear component for this term.