Electrochemical behaviour of pesticides at bare and nylon 6,6-modified solid electrodes in differential pulse cathodic stripping voltammetry

Abstract

The study of the voltammetric behaviour of five types of pesticides, namely paraquat dichloride, metsulfuron-methyl, lindane, chlorothalonil and glyphosate were carried out. The electrodes used were hanging mercury drop electrode (HMDE), glassy carbon electrode (GCE), HB pencil electrode (HBPE), boron doped diamond electrode (BDDE) and screen printed electrode (SPE). Due to the toxicity of mercury and to improve the detectivity for the determination of these pesticides, nylon-6,6 was used as modifier to modify the electrodes to produce nylon-6,6-modified glassy carbon electrode (Nyl-MGCE), nylon-6,6-modified HB pencil electrode (Nyl- MHBPE), nylon-6,6-modified boron doped diamond electrode (Nyl-MBDDE), and nylon-6,6-modified screen printed electrode (Nyl-MSPE). All measurements were performed using differential pulse cathodic stripping voltammetry technique (DPCSV) vs. Ag/AgCl (3.0 M KCl). Experimental parameters such as pH of Britton- Robinson buffer (BRB), accumulation time, accumulation potential and initial potential were optimized for the pesticides determination. Linear calibration plots for the paraquat dichloride and metsulfuron-methyl were obtained with the limit of detection (LOD) value of 3.66 × 10-8 M and 8.86 × 10?8 M, respectively on HMDE. The detectivity of DPCSV with nylon-6,6-modified solid electrodes were more effective compared to bare solid electrodes, where the LOD values for paraquat dichloride were 2.75 × 10-8 M (GCE), 6.42 × 10-9 M (Nyl-MGCE), 2.37 × 10-8 M (HBPE), 1.33 × 10-8 M (Nyl-MHBPE), 2.52 × 10-8 M (SPE), 1.05 × 10-8 M (Nyl- MSPE), 2.86 × 10-8 M (BDDE), and 1.54 × 10-8 M (Nyl-MBDDE). The novel sensors, Nyl-MSPE and Nyl-MHBPE were utilized for lindane and chlorothalonil analysis, and the LODs obtained were 4.26 × 10-8 M and 2.13 × 10-8 M, respectively. Efforts to study the electroactivity behaviour of metsulfuron-methyl and glyphosate were unsuccessful at all types of working electrodes that have been assessed in this study except HMDE for metsulfuron-methyl. There was no significant interfering metal ions effect found for voltammetric determination on the selected pesticides. Approximately 90% recovery was achieved for pesticides analyses. It can be concluded that the proposed DPCSV methods with nylon-6,6- modified solid electrodes were efficiently applied in this study and verified in real water samples analysis. The proposed DPCSV methods were also comparatively selective and have good coefficient of determination (R2 = 0.995).