Polyamide/silica/sodium alginate in-situ composite: Synthesis and application in electrochemical probing for Pb²⁺/Cd²

In this study, polyamide/silica/sodium alginate (SA) composite (PA-Si-SA) was successfully prepared in one-step benzoxazine-isocyanide chemistry (BIC)/sol-gel process at room temperature. The chemical structure and fundamental properties of PA-Si-SA were characterized by FT-IR, solid-state ¹³C NMR, XPS, XRD, SEM, BET and TG, etc. The presence of anionic SA and diverse N, O-containing functional segments (amide, tertiary amine, alkyl/phenol -OH, Si-O-Si, and COO^-) in PA-Si-SA endows it synergistic complexation capability toward Pb²⁺ and Cd²⁺. PA-Si-SA/GCE (glassy carbon electrode) fabricated by using PA-Si-SA as active modifier was applied to realize the efficient electrochemical detection of Pb²⁺/Cd²⁺. Relevant detection ranges, detection limits, anti-interference and detection mechanisms were systematically investigated further. Detection limits of Pb²⁺ and Cd²⁺ by PA-Si-SA/GCE were up to ~2.4 × 10^-8 mol/L and ~ 4.1 × 10^-9 mol/L, with corresponding linear detection ranges of 0.5-140.0 μmol/L and 0.01-140.0 μmol/L, respectively.