Efficient detection of metronidazole by a glassy carbon electrode modified with a composite of a cyclotriveratrylene-based metal–organic framework and multi-walled carbon nanotubes

Constructing a sensitive and efficient sensor for determination of metronidazole (MNZ) is crucial in food field. Herein, a new cyclotriveratrylene-based metal–organic framework (MOF), namely, [Cd6L2(cyclen)2(H2O)2] (1), was constructed by self-assembly of functionalized 5,6,12,13,19,20-hexacarboxy-propoxy-cyclotriveratrylene (H6L), 1,4,7,10-tetraazacyclododecane (cyclen) and Cd(II) cation under solvothermal condition. In 1, adjacent Cd(II) cations are linked by L6− to produce a 2D polymeric structure with carboxylate and phenolic oxygen atoms. To enhance conductivity of 1, it was combined with conducting carbon materials, including mesoporous carbon (MC), reduced graphene oxide (RGO) and multi-walled carbon nanotubes (MWCNT), respectively, producing a series of composite materials. Remarkably, electrochemical tests showed that 1@MWCNT(1:1) featured a much better electrochemical detection performance for metronidazole (MNZ) than 1@MC and 1@RGO. The linear range for the detection of MNZ is up to 0.4–500 μM and the limit of detection (LOD) for MNZ reached 0.25 μM. Importantly, the fabricated sensor 1@MWCNT(1:1) was employed for the detection of MNZ in honey and egg with satisfactory result. High-performance liquid chromatography (HPLC) validated the high accuracy of the electrochemical method for the determination of honey and egg.