Electrocatalytic and Sensors Properties of Natural Smectite Type Clay towards the Detection of Paraquat Using a Film-Modified Electrode

Abstract

In this study, a low-cost and sensitive voltammetric method was developed for the determination of paraquat (PQ<sup>2+</sup>). This was achieved by coating a glassy carbon electrode with a purified fraction of a smectite-type clay, which was then used to accumulate paraquat by an ion exchange process. The electronanalytical procedure involves two steps: the chemical preconcentration of paraquat under open-circuit conditions in an aqueous medium, followed by the voltammetric detection of the preconcentrated pollutant in a medium containing permanganate ions which significantly improved through its catalytic action the electrode response. A systematic study of the experimental conditions (pH of the accumulation and detection media, permanganate concentration in the detection medium, clay content of the coating, potential and duration of the electrolysis step) on the stripping response were examined in detail. After optimization, a linear calibration curve for paraquat was obtained in the concentration range from 1.6 to 2.8 µM, leading to a detection limit of 3.8 × 10<sup>–9</sup> mol·L<sup>–1</sup> (S/N = 3). The proposed method was successfully applied to the determination of paraquat in spring water

Signal amplification by electropolymerization of alizarin red S for improved diuron detection at organosmectite modified glassy carbon electrode

“…To solve this problem, surfactants have been used to modify and convert the hydrophilic surface into a hydrophobic surface. [21,24,25] Furthermore, in view of increasing the conductive capacities of electrode materials, the use of polymers is increasingly coveted, particularly the ones made with alizarin red S (ARS). ARS has high concentration of negatively charged functional group SO 3À and electron-rich oxygen atoms on its surface; [26,27] these active sites facilitate electrochemical deposition and strong cohesion of electroactive species, which therefore undergo electropolymerization easily to generate stable redox active layers.…”

“…1) where major changes are observed after modification of raw clay, and they can be explained as reported in previous works in the literature. [19][20][21][22][23][24][25] Figure 1 shows the X-ray diffraction (XRD) patterns of Sa(Na) and Sa(DODAB) samples. Significant differences were observed on the main peak around 2θ = 5.5 for the basal spacing (d 001 ), which correspond, by using Bragg relation (2dsinθ = λ), to 16 Å.…”

Square Wave Voltammetric Determination of Residues of Carbendazim Using a Fullerene/Multiwalled Carbon Nanotubes/Nafion®/Coated Glassy Carbon Electrode

“…The absorption bands at 3690 and 3625 cm −1 in NK3 sample and 3694 and 3619 cm −1 in NK1 sample correspond to interlayer hydroxyl group stretching of kaolinite in samples [24,25]. The absorption bands observed around 1400 and 1630 cm −1 in Figure 7 are ascribed, respectively, to C-H stretching vibration of organic matter and O-H deformation of molecular water [26,27], while the bands around 1000 and 910 cm −1 could be ascribed, respectively, to Si-O and Al-AlOH stretching vibration bands of kaolinite. Also, the band observed at 745-790 cm −1 can be ascribed to Si-O-Si intertetrahedral bridging bonds in silica contained in kaolinite as major mineral [25].…”

New Trends in Nanoclay-Modified Sensors

“…Herbicide detection has also been studied with CLME (Table 3) [20,21,[38][39][40][45][46][47]. Diverse electrode configuration has been tested, with paraquat being the most common analyte detected.…”

“…An example is the use of DDA-Saponite (SaDDA/GCE) vs. Na-Saponite (SaNa/GCE) for mesotrione detection [20] or organomontmorillonite film vs. sodium montmorillonite film/GCE for phenyl urea herbicide detection [21,45]. A particular case is the use of CLME for paraquat detection, where the use of raw smectites in the CLME resulted in good LOD and linear range [38,46,47]. The LOD of glyphosate by electrochemical electrodes based in carbon is higher than those based in metallic particle but they provided a wider concentration of range of detection [39].…”