Voltammetric determination of the herbicide Linuron using a tricresyl phosphate-based carbon paste electrode

Nanostructured graphitic carbon nitride (g-C3N4)-CTAB modified electrode for the highly sensitive detection of amino-triazole and linuron herbicides

In agro-areas, linuron (LNR) and amino-triazole (ATZ) are the widely used herbicides to protect crops, but their widespread use pollutes the environment, especially when these are mixed with water or soil. In efforts to address these environmental issues and to detect trace quantities of the herbicides, a graphitic carbon nitride (g-C₃N₄) with cetyltrimethylammonium bromide (CTAB) modified carbon paste electrode (g-C₃N₄-CTAB/CPE) was developed and used for the detection of LNR and ATZ. Materials were characterized by XRD, TEM and AFM techniques. The effect of pH on electro-oxidation (under optimized conditions) showed the maximum peak current at pH of 4.2 for AMT and pH 6.0 for LNR. The electro-kinetic and thermodynamic parameters of LNR and ATZ were determined. Additional experiments were performed for the trace level detection of ATZ and LNR using the square wave voltammetric technique. Concentrations were varied linearly in the range of 3.0 × 10^-7 M to 4.5 × 10^-5 M for ATZ with a detection limit of 6.41 × 10^-8 M, and 1.2 × 10^-7 M to 3.0 × 10^-4 M for LNR with a detection limit of 2.47 × 10^-8 M. The developed novel sensor was effective for trace level detection of LNR and ATZ in water and soil samples.

Analysis of herbicide and its applications through a sensitive electrochemical technique based on MWCNTs/ZnO/CPE fabricated sensor

The electrochemical performance of linuron (LNR) was studied by fabricating the carbon paste electrode (CPE) using multiwalled carbon nanotubes (MWCNTs) along with zinc oxide (ZnO) nanoparticles (MWCNTs/ZnO/CPE). The influence of electro-kinetic specifications involving steady heterogeneous rate, pH, sweep rate, temperature effect, transfer coefficient, accumulation time, activation energy, as well as the total number of protons and electrons participating in electro-oxidation of LNR has been established using voltammetric techniques like cyclic voltammetry (CV) and square wave voltammetry (SWV). These techniques were applied to investigate LNR in real samples such as soil including water samples. Over the 0.02 μM-0.34 μM ranges, a linear relationship was confirmed along with the limit of detection and quantification (LOD and LOQ) of the LNR. The synthesized ZnO nanoparticles were characterized by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD) analysis. The MWCNTs/ZnO/CPE sensor was considered sensitive for LNR detection because the sensor exhibited enhanced catalytic qualities with peak current in the involvement of 0.2 M phosphate buffer solution (PBS) of pH 6.0, attributed to the ultimate sensing performance of the sensor.

Two new polyoxometalate-based metal-organic complexes for the detection of trace Cr(VI) and their capacitor performance

Two new Keggin-type polyoxometalate (POM)-based metal-organic complexes (MOCs) H3[Cu2(4-dpye)2(PMo12O40)] (1) and H[Cu2(4-Hdpye)2(PMo12O40)(H2O)4]·2H2O (2) were constructed with a new N,N'-bis (4-pyrimidinecarboxamido)-1,2-ethane (4-H2dpye) ligand by the hydrothermal/solvothermal method. Complex 1 was a 2D layered structure constructed from 1D metal-organic chains [Cu(4-dpye)]n and Keggin-type [PMo12O40]3- polyoxoanions. Complex 2 displays a 3D supramolecular framework formed by discrete [PMo12O40]3- polyoxoanions and binuclear metal-organic loops [Cu2(4-Hdpye)2]. The electrocatalytic behaviors of carbon paste electrodes modified by complexes 1 and 2 (1-CPE and 2-CPE) were investigated. The 1-CPE and 2-CPE were used as electrochemical sensors to detect trace Cr(vi), and the low limits of detection (LOD) are 1.27 × 10-7 M for 1 and 1.71 × 10-7 M for 2, which are lower than the maximum allowable concentration of Cr(vi) in drinking water specified by the World Health Organization (WHO). In addition, the performances of complexes 1 and 2 modified carbon cloth electrodes (1-CC and 2-CC) as supercapacitor materials have also been studied. The influence of the structure on electrocatalytic and capacitor performances is discussed.

Glassy carbon and boron doped glassy carbon electrodes for voltammetric determination of linuron herbicide in the selected samples

In this study the application of home-made unmodified (GC) and bulk modified boron doped glassy carbon (GCB) electrodes for the voltammetric determination of the linuron was investigated. The electrodes were synthesized with a moderate temperature treatment (1000°C). Obtained results were compared with the electrochemical determination of the linuron using a commercial glassy carbon electrode (GC-Metrohm). The peak potential (E p ) of linuron oxidation in 0.1 mol dm−3 H2SO4 as electrolyte was similar for all applied electrodes: 1.31, 1.34 and 1.28 V for GCB, GC and GC-Metrohm electrodes, respectively. Potential of linuron oxidation and current density depend on the pH of supporting electrolyte. Applying GCB and GC-Metrohm electrodes the most intensive electrochemical response for linuron was obtained in strongly acidic solution (0.1 mol dm−3 H2SO4). Applying the boron doped glassy carbon electrode the broadest linear range (0.005–0.1 µmol cm−3) for the linuron determination was obtained. The results of voltammetric determination of the linuron in spiked water samples showed good correlation between added and found amounts of linuron and also are in good agreement with the results obtained by HPLC-UV method. This appears to be the first application of a boron doped glassy carbon electrode for voltammetric determination of the environmental important compounds.