Selective solid-phase extraction of trace Cu(II) and Mn(II) in complex food and water matrices using a hierarchical...

Quantifying trace heavy metals in complex food and environmental matrices requires sorbents with exceptional selectivity and matrix tolerance. We synthesized a ternary hybrid matrix (nano-HAP@Tween80@SG) via an ultrasound-assisted secondary coating approach, configuring it for the solid-phase extraction (SPE) of Cu(II) and Mn(II) prior to flame atomic absorption spectrometry (FAAS). Structural analyses (TEM, SEM-EDS, XRD, BET, FT-IR) confirmed the formation of a hierarchical assembly with extended mesoporosity. At an optimal pH of 5.0, metal adsorption followed the Langmuir and Freundlich models. The underlying sequestration mechanism is driven by a complex interplay of physical and chemical interactions: multi-dentate surface complexation and electrostatic attraction operate concurrently with the intrinsic thermodynamic ion-exchange capacity of the hydroxyapatite lattice, while the mesoporous network provides critical spatial confinement. Analytical performance proved highly competitive. Limits of detection were 0.022 µg L^-1 for Cu(II) and 0.024 µg L^-1 for Mn(II). The enrichment factors were 30 for Cu(II) and 29 for Mn(II), with relative standard deviations all below 3.0%. Method accuracy was validated against certified reference materials (wheat, rice) and actual environmental water samples, yielding recoveries between 95.50% and 103.33%. The nano-HAP@Tween80@SG-SPE-FAAS system functions as a practical, cost-effective platform for routine trace metal surveillance.