Construction of a Functional and Robust Cobalt(II) Phthalocyanine‐Modified Electrode for the Electrocatalytic Detection of Paraquat

Abstract

AbstractThis study explores the optimization and application of a gold‐modified electrode, CoPc‐cou‐f‐MWCNTs/3‐HT|Au, for the electrocatalytic detection of a water pollutant, paraquat (PQ). It was fabricated via a sequential modification procedure entailing the formation of self‐assembled monolayers (SAMs) of a nanocomposite comprising of a coumarin tetra‐substituted cobalt phthalocyanine (CoPc‐cou) and carboxylic acid functionalized multiwalled carbon nanotubes (f‐MWCNTs). This was followed by the in‐situ immobilization of poly(3‐hexylthiophene) ([3‐HT]n) through electropolymerisation to render the chemically modified electrode (CME). Subsequently, the CME illustrated enhanced sensitivity towards PQ compared to the bare or CoPc‐cou‐f‐MWCNTs modified electrodes. The CoPc‐cou‐f‐MWCNTs/3‐HT|Au electrode displayed a linear PQ detection range of 0.584–1000 μM with a limit of detection (LOD) and limit of quantification (LOQ) of 0.193 μM and 0.584 μM, respectively. Comparison between calibration curves for the modified electrode and HPLC‐MS illustrates that the former method has a lower but comparable calibration sensitivity for PQ. In addition, this CME could electrocatalytically distinguish PQ within a real water sample collected from the Durban lagoon. Furthermore, the direct recovery of PQ in the lagoon water by the modified Au electrode was found to be 86 %, which is lower than the calculated value of 97 % obtained by HPLC‐MS after rigorous solid‐phase microextraction of the analyte. However, the lower percentage recovery could be rationalized by the interference studies.