Carbon nanotube grafted pyridinuim compound as a neutral ion-carrier of carbon paste electrode for sub-nanomolar simultaneous monitoring of Cu (II) and Hg (II)

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ABSTRACT Multi-walled carbon nanotube (MWCNT)-grafted 2, 6-bis[2-(amino methyl)phenol]pyridine (BAPP) synthetic ligands were effectively used as novel ion carriers in the structure of carbon paste electrodes (CPEs) for simultaneous trace-level assessment of Hg(II) and Cu(II) by potentiometry. Utilising pyridine-based Cu(II) and Hg(II) complexing agents and MWCNTs as signal boosters has reasonably eventuated in an acceptable sensitivity and selectivity over Cu(II) and Hg(II) target ions in the presence of some interfering species. The working linear range, limit of detection, and Nernstian slope of the sensor were recorded as follows, respectively, Hg(II): 4.0 × 10−9 to 3.0 × 10−4 mol L−1, 2.0 × 10−9 mol L−1 and 43.2 (±0.4) mVdecade‒ 1 (n = 5) and Cu(II): 4.0 × 10−9 to 2.2 × 10−2 mol L−1, 7.9 × 10−10 mol L−1 and 29.8 (±0.5) mVdecade‒ 1 (n = 5). The working pH range of 3.0‒4.5 and 4.0‒7.0 and dynamic response time of 7.0 s and 5.0 s were evaluated for the Hg(II) and Cu(II) sensors, respectively. The modified sensors also displayed an acceptable reproducibility, response repeatability and useful lifetime over around 45 days. Eventually, the practical utility of the chemically modified sensors was confirmed by trace-level potentiometric monitoring of mercury and copper ion quantities in some environmental, industrial and biological aqueous samples.