An amino-modified metal-organic framework (type UiO-66-NH2) loaded with cadmium(II) and lead(II) ions for simultaneous electrochemical immunosensing of triazophos and thiacloprid

A method is described for simultaneous voltammetric determination of the pesticides triazophos (TRS) and thiacloprid (THD). A glassy carbon electrode (GCE) was modified with a metal-organic framework (type UiO-66-NH2) which has a large specific surface (1018 m2·g-1) and contains large amounts of Cd(II) and Pb(II) ions, with adsorption capacities of 230 and 271 mg·g-1, respectively. The antigen-loaded particles were then bound to antibody, magnetically separated, and analyzed by square wave voltammetry to give signals for Cd(II) and Pb(II) at -0.82 and - 0.56 V (vs. Ag/AgCl) for TRS and THD, respectively. Under optimized conditions, the method has a wide linear range (0.2-750 ng·mL-1) and low detection limits (0.07 and 0.1 ng·mL-1 at a S/N of 3 for TRS and THD, respectively). It is perceived that this assay represents a useful tool for simultaneous determination of multiple pesticide residues. The method has a wide scope in that may be extended to monitoring of other small organic pollutants by changing the types of metal ions and by using other antibodies. Graphical abstract Schematic presentation of an amino-modified metal-organic framework (type UiO-66-NH2) loaded with Cd(II) and Pb(II) ions for simultaneous electrochemical immunosensing of triazophos (TRS) and thiacloprid (THD). It is based on the fabrication of antigen (Ab)-immobilized UiO-66-NH2-based signal tags (a), and of an antibody (Ab)-immobilized magnetic bead (MB-COOH)-based capture probes (b).