Green citrate sol–gel synthesis of CuMn₂O₄/Dy₂O₃ nanocomposite for efficient separation, preconcentration, and determination of Cd(II) in food and environmental samples

A novel CuMn₂O₄/Dy₂O₃ nanocomposite was synthesized and applied as an efficient adsorbent for the trace Cd(II) using micro solid-phase extraction (µSPE) coupled with high-resolution continuum source flame atomic absorption spectrometry (HR-CS-FAAS). The nanocomposite was prepared via a green, facile citrate sol–gel route followed by thermal annealing and was extensively characterized by FT-IR, XRD, SEM–EDX, BET, and TGA analyses. Key extraction parameters, including pH, adsorbent dosage, contact time, eluent type, and sample volume, were systematically optimized. Under the optimized conditions (pH 7.0, 7.5 mg adsorbent dosage, 1.0 mL of 1.0 M HNO₃ as eluent, and 40.0 mL of sample volume), the method achieved a preconcentration factor of 40. The procedure exhibited an instrumental LOD of 5.2 µg L⁻ 1 , corresponding to a method LOD of 0.13 µg L⁻ 1 after accounting for the preconcentration factor of 40 below both the WHO and US EPA drinking water guideline values for cadmium together with high selectivity in the presence of competing ions. The analytical accuracy and robustness of the method were validated using certified reference materials. Its applicability was successfully demonstrated with commercial chocolate, juice, and wastewater samples.