Novel green synthesis of Al-Fe₃O₄ nanocomposite for magnetic d-μSPE of Cd(II) from water and food samples

A novel and green nanocomposite (Al-Fe₃O₄) was synthesized and used for the magnetic d-μSPE method for separating and enriching Cd(II) from dried fruit samples. Aluminum foil waste and banana peels were used as the precursors. The green nanocomposite was characterized using FTIR, XRD, and FE-SEM techniques. The characterization results indicated a successful synthesis with active sites for efficient and simple extraction. The method performance showed significant results of low limits of detection (LOD) and quantification (LOQ) of 0.068 and 0.227 μg L^-1, respectively. The method demonstrated an efficient extraction time of just 15 s using hand shaking. The optimal parameters were determined as pH 8.0, an adsorbent amount of 5 mg, adsorption and desorption intervals of 15 s and 0.5 min, a sample volume of 30 mL, and an eluent volume of 3.0 mL of 0.1 mol L^-1 of HNO₃. The greenness degree of both the synthesis and magnetic d-μSPE methods was evaluated, which achieved high eco-scale and greenness scores of 94 and 0.79, respectively. The detected Cd(II) levels in the food samples were 10.2, 17.0, 27.4, and 18.8 μg kg^-1 for dried Granny Smith apples, dried apricots, raisins, and dried kiwi, respectively. The developed method demonstrated exceptional sensitivity and reliability, successfully extracting Cd(II) at ultra-trace levels.