## 3 Results
### Evaluation of Mesoporous Silicas as Sorbents in SPE
To investigate this, increasing volumes (5, 10, and 20 mL) of 0.1 \(\upmu\)g/L atropine and scopolamine solutions  
Figure 11: Atropine and scopolamine recoveries (% \(\pm\) SD) obtained in SPE assays using 50 mg of MSU-2-SO\({}_{3}\)H or MCM-41-SO\({}_{3}\)H as sorbents when the target analytes were loaded in 10 mL of acidified (pH 1) ethanol or water (0.1 \(\upmu\)g/L of each analyte) and eluted with 3 or 6 mL of 5% methanolic ammonia solution. For the remaining conditions, see Figure 2. Error bars represent the standard deviation of replicate samples (\(n=3\)). In each graphic, a different letter indicates a statistically significant difference (\(p\leq 0.05\)). in acidified (pH 1) EtOH and H\({}_{2}\)O were passed through the SPE cartridges containing 50 mg of MCM-41-SO\({}_{3}\)H or MSU-2-SO\({}_{3}\)H as sorbents. As seen in Figure 12, when the loading solvent was H\({}_{2}\)O, no significant differences were observed in the recoveries of both analytes with both materials. However, when the loading solvent was EtOH, there was a significant reduction in retention capacity when increasing the loading volume from 10 to 20 mL. This effect was more pronounced when the sorbent was MSU-2-SO\({}_{3}\)H (recoveries around 25%) compared to MCM-41-SO\({}_{3}\)H (recoveries around 60%). These results can be explained by polar interactions, especially hydrogen-bond interactions of EtOH tend to reduce retention by the sorbents and result in smaller breakthrough volumes. Therefore, if the solvent most suitable for the prior solid-liquid extraction of analytes is EtOH, the low breakthrough volume observed with this loading solvent should be considered to achieve adequate recoveries, which is especially necessary for very diluted extracts. Finally, additional experiments were carried out to evaluate the adsorption capacity of these materials, maintaining the optimal loading volume of 10 mL. These studies were carried out in a concentration range of 0.1-30 \(\upmu\)g/L and 50 mg of MCM-41-SO\({}_{3}\)H and MSU-2-SO\({}_{3}\)H as a sorbent (Figure 13). As can be observed, the adsorption capacity of MCM-41-SO\({}_{3}\)H was superior to that of MSU-2-SO\({}_{3}\)H in both solvents. For MSU-2-SO\({}_{3}\)H, the increase in analyte concentration resulted in a significant reduction in retention for both analytes when the solvent was EtOH, with recoveries as low as 10% for a concentration of 10 \(\upmu\)g/L. Similarly, for MSU-2-SO\({}_{3}\)H, the increase in analyte concentration from 0.1 to 10 \(\upmu\)g/L led to a significant reduction in recovery, with recoveries of approximately 80% for 10 \(\upmu\)g/L. However, when the loading was performed in H\({}_{2}\)O, the increase in concentration up to 30 \(\upmu\)g/L resulted in a significant reduction in recovery when the sorbent was MSU-2-SO\({}_{3}\)H, which was more evident for scopolamine (recoveries around 45%). In contrast, for MSU-2-SO\({}_{3}\)H, as shown in Figure 13, this same concentration allowed for recoveries close to 100% for both analytes. These results demonstrated the effectiveness of MCM-41-SO\({}_{3}\)H as a sorbent material for SPE of propane alkaloids in aqueous samples or extracts. Figure 12: Atropine and scopolamine recoveries (% \(\pm\) SD) obtained in SPE assays using 50 mg of MSU-2-SO\({}_{3}\)H or MCM-41-SO\({}_{3}\)H as sorbents when the target analytes were loaded in 5, 10, or 20 mL of acidified (pH 1) ethanol or water (0.1 \(\upmu\)g/L of each analyte) and eluted with 6 mL of 5% methanolic ammonia solution. For the remaining conditions, see Figure 2. Error bars represent the standard deviation of replicate samples (\(n=3\)). In each graphic, a different letter indicates a statistically significant difference (\(p\leq 0.05\)).