## 2 Results and Discussion
### Performance of the Prepared Fibers  
After the optimization of the SPME parameters to attain a maximum of total peak areas for pD14, extractions were carried out with the other two fibers (pD2 and pD8) at these fixed conditions. The extraction efficiencies for each fiber and the total detected areas are presented in Figure 6a, along with the results obtained for the commercial PDMS7 and PA85 fibers under the same experimental conditions. Since our standard solution is a mixture of polar and semi-volatile compounds, but it also contains rather less polar compounds with relatively long alkyl chains, such as in 1-octanol or 2-heptanone, two commercial fibers were chosen to establish comparisons with our homemade fiber: PA85, that is a suitable and recommended SPME phase for polar and semi volatiles, and PDMS7, that is a SPME phase recommended for non-polar molecules with molecular weights of 125 up to 600. More complex commercial SPME fibers, such as PDMS/DVB or others, were avoided since we want to establish a fair comparison with other pure polymers. An increase in the overall extraction efficiency can be observed with the increase of the alkyl chain length, from pD2 to pD14. This behavior can be attributed to a more packed structure obtained for pyrrolinium-based PILs with shorter chains, yielding a material with smaller free volume [37]. Conversely, for a material with longer alkyl chain lengths, the free volume increases, and therefore, the analytes can better accommodate, diffuse, and penetrate into the material resulting in superior extraction efficiencies. The increase of the alkyl chain length does not seem to have much effect on the extraction of polar compounds, such as 1-butanol, where similar peak areas were obtained for pD2, pD4, and pD14. In terms of total detected peak areas, pD14 presents 56% and 68% higher efficiency than pD8 and pD2, respectively. From the obtained results shown in Figure 6a, it can be observed that the overall pD14 fiber showed the best results, with a 55% higher total peak area than the PDMS fiber with 7 \(\upmu\)m and more than 90% total peak area higher than the PA fiber with 85 \(\upmu\)m. Apart from the different chemical nature of each polymer, the difference in the film thickness between our coatings (67 \(\upmu\)m) and the commercial coatings used here PDMS (7 \(\upmu\)m) and PA (85 \(\upmu\)m) is an important factor affecting the efficiency of our fibers since increasing the film thickness can lead to longer extraction times, due to a slower mass transfer. Thus, the construction of a thinner PIL coating will fasten the mass transfer in the desorption step, therefore, possibly increasing the performance of the PIL fibers. Moreover, it is known that fibers that are vitreous solids at room temperature, such as the PA fiber, take more time to sorb analytes unless high temperatures are used. In terms of individual compounds (Figure 6b), similar sorption profiles were observed for the three prepared fibers for all of the components in the prepared mixture, probably due to the small change in the materials properties owing to the lack of functional groups in the alkyl side chains of the prepared materials. However, it is notorious that the sorption of analytes with longer chains, such as 1-octanol, increases with the increasing of the alkyl chain length in our material, in agreement with what was said before for the increase in the free volume with the increase of the alkyl chain length. On the other hand, molecules such as cyclopentanone or benzyl alcohol do not show much affinity towards any of the prepared fibers. To better understand these behaviors, properties such as the vapor pressure (\(V_{P}\)), molar volume (\(V_{M}\)), and water solubility (\(W_{S}\)) of each compound must be taken into account. First, higher water solubility will obstruct the extraction from the aqueous phase to the headspace. Second, the higherthe molar volume, the less absorption within the polymer is achieved.