## 3 Results and Discussion
### Optimizing the Developed Solid-Phase Microextraction onto SSC-MOFs  
The promised features of the metal-organic frameworks, such as their porosity and high adsorption capability, have led to efficient microextraction applications [45; 46; 69; 70; 71; 72; 73]. Herein, a microextraction method for the separation of arsenic(III) traces was established using the prepared SSC-MOFs. The process of the microextraction procedure was enhanced by the ability of the adsorbent (a solid support material) to disperse in the sample extract solution and attract the targeted analyte species during the adsorption process to achieve the complete transfer of mass and settlement on the surfaces and pores of the SSC-MOFs. The pH of the sample extract was reported to be a highly influencing factor in the adsorption process and the control efficiency of the microextraction procedures [74; 75; 76]. Therefore, in this work, the effect of pH was studied in the range between two and eight. The recovery% of the pH investigation is presented in Figure 6A. A low recovery% was achieved in theacidic medium; however, a higher recovery% was obtained in the pH range between six and eight. This may be because the lower-pH medium was rich with H ions, which resulted in the protonation of the functional group, including a reduction in the interaction with the arsenic(III) ion species. A pH of 7 was selected as the optimum condition for the further optimization of the microextraction of arsenic(III) using the formulated SSC-MOFs. The effectiveness of the microextraction procedures applied in this work is illustrated in Scheme 1, which showed the porosity structure and the active surface functional groups such as C=N and N-H. These active groups enhance Vander Waals forces and dipole-dipole interaction and facilitate the collection and attraction of arsenic from the aqueous sample solution during the microextraction process. In addition, the effect of the shaking time during the adsorption stage on the recovery% was studied for the microextraction mixture, including the sample extract and the SSC-MOFs. The tested time intervals included 1, 3, 5, 8, 10, 12 and 15 min, as presented in Figure 6B. After 10 min, the recovery% was 99%, indicating the efficiency of the process for preconcentrating arsenic(III) from aqueous samples. The contact time of 10 min during the adsorption stage was demonstrated to be the optimum time for the mass transfer of trace arsenic(III) from the aqueous sample solution to the adsorbent's surface. The next step for optimizing the microextraction process was to determine a suitable eluent solution for the desorption stage. For this purpose, solutions of 0.1, 0.3 and 0.5 M of HCl as well as 0.05, 0.1 and 0.3 M of HNO3 were applied, and the recover% values are shown in Figure 6C. The HCl-derived solutions exhibited the lowest efficiency for eluting the arsenic(III) from the SSC-MOFs; however, the diluted nitric acid solutions were the most efficient for the elution process, reporting recovery% values of 99, 98 and 99 for 0.05, 0.1 and 0.3 M of HNO3, respectively. Figure 1: The SEM images of the fabricated SSC-MOFs at magnifications of (**A**) 200 and (**B**) 1000 and the (**C**) EDS analysis. Figure 3: The porosity investigation using an adsorption/desorption nitrogen isotherm. Figure 2: The TEM images of the fabricated SSC-MOFs at magnifications of (**A**) 50,000 and (**B**) 30,000. Figure 4: The FTIR spectrum of the fabricated SSC-MOFs. Figure 5: The XRD pattern for the fabricated SSC-MOFs. The crystalline structure of the fabricated SSC-MOFs, as well as the surface functional groups, enable the adsorbent to be used multiple times after it is regenerated by being washed with ethanol and water. The regeneration process was repeated eight times with an efficient performance of the microextraction of arsenic(III), with a recover% of about 98 (Figure 6D).