Zn-based metal-organic frameworks and p-aminobenzoic acid for electrochemical sensing of copper ions in milk and milk powder samples

Abstract

ABSTRACT Copper is an essential mineral that plays a vital role in the body, which in the event of an increase it can be toxic to the body. The concentration of copper in the blood is very important. In the present study, a surface-modified glass electrode bead on Metal–organic frameworks (MOFs) and p-aminobenzoic acid (PABA) is presented and used for rapid, simple, selective and highly sensitive determination of copper using differential pulse adsorptive stripping voltammetry. A novel Zn-based metal-organic framework, (Zn-TMU-24) through a solvothermal method, is constructed and investigated by different spectra such as FT-IR, SEM and TGA. Then, the Zn-TMU-24 is conjugated with PABA via electrochemical polymerisation to form PABA-MOF on surface glass electrode. The amide-functionalised groups in the structure of PABA-MOF have provided a potential for chemical interaction with a metal ion Cu2+, and used for the fast detection of Cu2+ in milk and milk powder as real samples. The interaction between the proposed Zn- TMU-24 and Cu2+ was characterised by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The calibration plot is linear in the concentration range of 0.05 to 250 nM with detection limit of 0.014 nM. The excellent stability of the proposed electrode was observed. The proposed sensor was successfully applied to the analysis of milk and milk powder samples.