Selective magnetic extraction of calcium-based food additives using polystyrene sulfonate-functionalized starch magnetic particles

Analysis of nano-sized calcium carbonate (CaCO₃) and tricalcium phosphate (Ca₃(PO₄)₂) in food is critical for safety assessment but is hindered by complex food matrices. Because conventional extraction methods irreversibly alter nanoparticle properties, we developed a gentle magnetic separation technique. Starch magnetic particles functionalized with polystyrene sulfonate (PSS@SMPs) demonstrated high selectivity, capturing ∼80% of target calcium additives with negligible affinity for other inorganic additives like TiO₂, SiO₂, and ZnO. A subsequent elution step using polyethyleneimine enabled high recovery rates (∼85–90%). SEM, XRD, and EDX analyses confirmed the recovered nanoparticles retained their pristine size, morphology, and crystallinity. The method proved effective in commercial foods, achieving 50–80% recovery from complex matrices like chewables and creams, thereby enabling accurate downstream analysis for risk assessment.