Hybrid CTAB–Silica and APTES-Functionalized Multi-Walled Carbon Nanotubes for Adsorption-Enhanced Electrochemical Detection of Bisphenol A in Environmental and Food Samples

Bisphenol A (BPA) is an industrial chemical and emerging environmental contaminant whose presence in water and food at low concentrations poses health risks. Here, we developed a hybrid nanocomposite electrode combining cetyltrimethylammonium bromide–incorporated silica (CTAB@SiO 2 ) and 3-aminopropyltriethoxysilane (APTES)-modified multi-walled carbon nanotubes (MWCNTs) for electrochemical BPA detection. CTAB@SiO 2 provides a porous, positively charged matrix to enhance BPA adsorption and preconcentration, while APTES-functionalized MWCNTs ensure efficient electron transport and structural stability on a glassy carbon electrode. The sensor exhibits enhanced voltammetric response, which is consistent with adsorption-assisted accumulation and increased electroactive surface area. Under optimized conditions, three distinct linear ranges were obtained (1.5 × 10 –9 –1 × 10 –8 M, 1 × 10 –8 –1 × 10 –7 M, and 1 × 10 –7 –1 × 10 –6 M), reflecting adsorption-controlled, mixed adsorption–diffusion, and diffusion-controlled regimes, respectively, with a detection limit of 1.2 × 10 –9 M (S/N = 3) and a sensitivity (up to 3.13 × 10 8 A·M −1 ·cm −2 in the ultra-trace range). The electrode demonstrated good repeatability, selectivity, and stability, with recoveries in spiked environmental and food samples ranging from 96.0% to 102.4%. These results results highlight CTAB@SiO 2 @MWCNT–APTES as an adsorption-enhanced platform for BPA monitoring, while further validation in naturally contaminated samples is needed to confirm ultra-trace performance.