## 3 Results
### Optimization of the SB-MSPE Procedure
A variety of masses were examined (5, 10, 20, 30, 40, 50, 60 and 70 mg) and according to Figure 8, the optimum mass was 40 mg. When mass > 40 mg is used, a small increase is observed, while the use of <40 mg leads to a significant increase. Additionally, 40 mg was selected because it is considered a low mass, making the microextraction method greener. Four volumes of the sample were assessed to obtain the greatest results. The former two volumes (10 and 20 mL) of the sample were added in a glass vial with the capacity of approximately 30 mL, while the latter two (50 and 100 mL) were put in glass beakers of 100 and 250 mL, respectively. The concentration of the analytes was the same in all four volumes, viz 10 ng/mL. In Figure 9, the diagram of the absolute recoveries is shown. Figure 8: Diagram of the normalized absolute recoveries of the different masses of the adsorbent according to the 40 mg.  
Figure 7: Bar diagram of the normalized absolute recoveries of the different volumes of the elution solvent according to 0.5 mL. The effect of the duration of extraction and elution are two important factors that directly influence the extraction efficiency and the time needed for the whole method. Thus, different durations were investigated for the extraction (5, 10, 20, 30 and 40 min) and the elution (1, 5, 10, 15 and 20 min). The optimal durations are 30 min for the extraction, due to the vast gap between 20 and 30 min, and 10 min for the elution (Figure 10). Figure 10: Bar diagram of the normalized absolute recoveries of the different durations of extraction (above) and of the elution (below) according to 30 min and 10 min, respectively. Figure 9: Diagram of the absolute recoveries of the different sample volumes that were examined. Another important parameter is the speed of stirring and the usage of ultrasonication. The speeds that were examined were 0, 425, 750, 1125 and 1400 rpm and the optimal was the 750 rpm, according to the bar diagram of Figure 3:0 For speeds > 750 rpm, a decline is observed, possibly since it was too fast and the interactions between the compounds and the adsorbent could not be established. The addition of salt (namely NaCl) was investigated because the surface water samples, primarily the sea water samples, contain some dissolved salts. Besides trying to mimic the salinity of sea water samples, we wanted to check if the addition of extra NaCl would increase or not the recoveries of the extraction Hence, the addition of 0, 5, 10, 15 and 20% \(w/v\) of NaCl in the 10 mL of the sample volume was examined and it was noticed that the lower the percentage content, the better the absolute recoveries (Figure 12). Moreover, the phenomenon of precipitation of the nanocomposite was observed in high salt contents, rendering the analysis of surface water samples that have a high concentration of dissolved salts difficult. The pH value affects the degree of ionization of the two benzodiazepines, so four values were studied. For this purpose, 10 mL of 1% \(v/v\) acetic acid, 10 mL of buffer solution  
Figure 3:1 Bar diagram of the normalized absolute recoveries of the different speeds of stirring and the application of ultrasonication according to 750 rpm. Figure 3:2 Bar diagram of the normalized absolute recoveries of the different percent content (% \(w/v\)) of salt according to the optimal 0%. of 0.5 M acetic acid--0.5 M sodium acetate, the addition of 10 mL deionized water and 10 mL of 1% \(w/v\) sodium acetate were prepared to reach the desired pH values of 3, 5, 7 and 9, respectively. The highest recoveries were acquired at a pH value of 7, where both ALP and FLT were 100% unionized and no extra reagents were used to change the pH value (Figure 13). Finally, the effect of activating the functional groups of the adsorbent was examined by following the optimized thus far protocol. Two steps were added before the extraction, one step with the immersion of the adsorbent in 2 mL of MeOH and one step with the addition of 2 mL of deionized water.