Metal–organic framework modified carbon paste electrode for lead sensor

Metal–organic framework (MOF) is a relatively new group of interesting materials for specific electrochemical sensing because of its electrocatalytic activity and large surface area. Here, a Zn4O(BDC)3 (MOF-5; BDC2− = 1,4-benzenedicarboxylate) modified carbon paste electrode for lead detection was developed. The electroanalytical procedure comprised two steps: chemical accumulation of the adsorbed metal ions at the modified electrode surface, followed by electrochemical detection of the pre-concentrated species using differential pulse stripping voltammetry. It was found that the MOF-5 was capable of adsorbing lead ions from aqueous solutions and could determine the ions prominently at optimum experimental conditions. Many important parameters to acquire the best electrochemical response were carried out, including the amount of MOF-5, different electrolyte solutions, pH, deposition potential, deposition time, and interferences due to other ions. Finally, a calibration graph was obtained with a linear range from 1.0 × 10−8 to 1.0 × 10−6 mol L−1 (R2 = 0.9981) and detection limit was found to be 4.9 × 10−9 mol L−1. The relative standard deviation (for n = 11) was 3.4% at 1.0 × 10−7 mol L−1 of lead level. The proposed method was used for the determination of lead in the real water samples and standard reference materials.