Dispersive solid phase extraction using SiO₂@ZIF-8@Fe₃O₄ core-shell nanoparticles for extraction of Cd(ii), Zn(ii),...

Monitoring heavy metal contaminations in food and beverage products is essential for ensuring public health. However, most existing extraction techniques suffer from low selectivity, limited sensitivity, and time-consuming sample preparation steps. To overcome these limitations, a dispersive micro solid phase extraction (D-µSPE) method was developed using SiO₂@ZIF-8@Fe₃O₄ core-shell nanoparticles; a composite material that combines high surface area, magnetic separation capability, and chemical stability, and has not been previously applied for this purpose. The synthesized nanocomposite was employed for the adsorption of Cd(ii), Cu(ii), and Zn(ii) ions from fruit juice samples, followed by desorption with diluted nitric acid solution and quantification by flame atomic absorption spectrometry. The main experimental parameters including sorbent amount, extraction and desorption times, solvent type and volume, pH, and salt addition were systematically optimized. Under optimized conditions, the linear ranges of the calibration curves were established in the ranges of 0.5-100, 0.8-80 and 1.2-75 µg L^-1, for Zn(ii), Cu(ii), and Cd(ii) ions, respectively. The detection limits were found to be 0.4, 0.3 and 0.2 µg L^-1 along with the extraction recoveries of 95.2, 96.8, and 98.1% for Cd(ii), Cu(ii), and Zn(ii) ions, respectively. The repeatability of the established method, indicated by relative standard deviation, was less than 5% for intra-day (C = 25 µg L^-1, n = 6) and inter-day (C = 25 µg L^-1, n = 4) precisions. The developed approach was successfully applied to various commercial fruit juice samples and validated using a certified reference material. This study introduced a rapid, low-cost, and eco-friendly strategy for trace-level monitoring of heavy metals in food matrices, highlighting its strong potential for routine food quality control and public health protection.