## 3 Results and Discussion
### Chromatographic Performance of the Mono and Cross-Linked Ionic Liquid Stationary Phase  
In order to obtain additional information on the morphologies and physical-chemical properties of the PIL-based columns prepared, as well as on their potential for efficient chromatographic separations, the Grob test was injected into each of the prepared stationary phases and the results obtained were analyzed. The Grob test contains a mixture of compounds of different nature, and is used to evaluate the separation efficiencies, the acid and basic characteristics, and the relative polarity of chromatographic columns [56; 57]. The mix contains various types of organic compounds including hydrocarbons, fatty acids methyl esters, acids, bases, and alcohols, and each peak gives specific information on the column. Alkanes (n-decane and n-undecane) represent a 100% recovery marker and should have symmetrical peaks if the column was correctly prepared. Alcohols (1-octanol and 2,3-butanediol) are used to measure the adsorption caused by hydrogen bonding mechanisms. The acid/base interactions are shown by the behavior of 2,6-dimethylaniline, 2,6-dimethylphenol, dicyclohexylamine, and 2-ethylhexanoic acid. Fatty acid methyl esters (methyl decanoate, methyl undecanoate, and methyl dodecanoate) are a homologous series of fatty acid methyl esters used to determine the separation efficiency of the column. Thus, the use of this mixture of compounds of different nature can allow the determination of the influence of the DVB content in the polymerization mixtures on the general properties of the column and also to assess their suitability as GC columns for analytes of different nature. The chromatograms obtained with columns PIL40 and PIL60, based on mixtures of the vinylic AAIL and 40% and 60% of DVB, respectively, are not shown and will not be discussed as an appropriate separation of the compounds was not observed. Figure 4 shows the results obtained for the other PILs. For a proper comparison, the chromatograms have been represented at the same scale. Figure 4a,b display the results for the stationary phases prepared in the absence of crosslinking (PIL00) and with just 10% of DVB (PIL10), respectively, and reveal that all compounds exhibited high peak tailing. This indicates that the coating films generated throughout the silica capillary are not homogeneous, and that nonspecific adsorptions with residual accessible silanols can be present. Furthermore, 1-nonanal and 1-octanol show both peak tailing and reduced peak heights, which implies that these stationary phases are highly polar with H-bond accepting capabilities. Figure 4c, representing the results for the stationary phase prepared with 20% DVB (PIL20), shows the best peak symmetries and less mass transfer losses, which is in agreement with the previously discussed solvation parameter coefficients results and with the results for the calculation of the theoretical plates number. In this column, the alkanes were better-separated from the solvent peak as compared with the other columns studied, and the fatty acid methyl esters were separated with good symmetries and good separation efficiencies. Moreover, better peak symmetries and lower mass transfer losses were also observed for 2,3-butanediol, 2-ethylhexanoic acid, and dicyclohexylamine using the PIL20 column than using the commercial imidazolium IL82 and IL100 columns [23]. This suggests that this column can be of practical application to quantify low levels of compounds with a high capability to interact through H-bonding. It must be noted that the results were again worse when a higher crosslinking degree was used (PIL30, 30% DVB, Figure 4d), the corresponding chromatogram displaying lower separations and less symmetric peaks. Although not all the analytes were separated using these PIL columns, it should be noted that in all columns studied, 2,3-butanediol and 1-octanol eluted after decane and undecane.