Applicability of a synthesized melamine based covalent organic framework as a novel ionophore for the potentiometric determination of mercury (II): Computational and experimental studies

In this research, the complexation of a recently synthesized covalent organic framework (schiff base network1) with 10 different cations was investigated by QTAIM (quantum theory of atoms in molecules) computations. The theoretical results showed the schiff base network1 interactions with Hg2+ is considerably stronger than other cations and it can be used as an selective ionophore for the development of a potentiometric sensor to determination of Hg2+. Therefore, a Hg2+ selective PVC membrane coated graphite electrode was developed based on schiff base network1. The best response was observed form the membrane composition of PVC (32 %), Nitrobenzene (60 %), sodium tetraphenylborate (2 %), and schiff base network1 (6 %). The designed sensor showed an excellent Nernstian response to Mercury (II) (29.8 mV. Decade  1) over a wide activity range from 1 x 10 7 to 5 x 10  3 and the detection limit of the proposed potentiometric sensor was 8 x 10 8. The effect of different interfering species on the potentiometric response of the suggested electrode was scrutinized by matched potential method (MPM) and no interference was observed. The performance of the developed electrode in partially non-aqueous mediums was also checked out and the obtained results showed the electrode can also be utilized in systems containing %20 organic solvents (ethanol and acetone). The response time and lifespan of the electrode were <10 S and 16 weeks respectively. In the end, the analytical performance of the fabricated sensor for the determination of Hg (II) in three different effluent samples was scrutinized and the obtained results were compared with a standard spectrophotometric technique.

Automated summary

In this research, the complexation of a newly synthesized covalent organic framework (schiff base network1) with different cations, including Hg2+, was studied. The results showed that schiff base network1 had a stronger interaction with Hg2+ compared to other cations, making it a potential ionophore for the development of a Hg2+ potentiometric sensor. A Hg2+ selective PVC membrane coated graphite electrode was successfully created using schiff base network1, which exhibited excellent response and sensitivity for the detection of Hg2+ in a wide range of concentrations. The electrode also demonstrated good performance in non-aqueous environments and had a long lifespan.