Single-drop detection of sulfamethoxazole in milk using MOF@MIP electrochemical sensor with DFT-guided imprinting strategy.

The study presents the development of a disposable electrochemical sensor based on lanthanide metal-organic frameworks (Ln-MOFs) and molecularly imprinted polymers (MIPs) for detecting the veterinary antibiotic sulfamethoxazole (SMX) in single-drop mode. The Ln-MOF was synthesised using La(NO3)3 and 1,3,5-tris(4-carboxyphenyl)benzene (H3BTB), yielding La-BTB, followed by modification of the screen-printed gold electrode (SPGE) with La-BTB. DFT calculations were used to investigate the formation of the pre-reaction complex prior to the molecular imprinting process, on the basis of which the most suitable functional monomer (FM) was identified and selected. The MIP was formed on the SPGE/La-BTB electrode via electropolymerization using o-phenylenediamine (oPD) as FM. The developed MOF@MIP-based sensor detects SMX over a wide concentration range (1 pmol/L to 11 μmol/L), providing a picomolar detection limit of 0.6 pmol/L. The proposed platform was successfully applied to detect SMX in milk and tap water, confirming its substantial potential for point-of-care implementation in real-matrix analysis.