The first study of triazole fungicide difenoconazole oxidation and its voltammetric and flow amperometric detection on boron doped diamond electrode

• Published in: Electrochimica acta Vol. 381; p. 138260
• Main Authors: Šelešovská, Renáta, Schwarzová-Pecková, Karolina, Sokolová, Romana, Krejčová, Kateřina, Martinková-Kelíšková, Pavlína
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 10.06.2021; Elsevier BV
• Subjects: Aqueous solutions; Boron; Boron doped diamond electrode; Confidence intervals; Diamonds; Difenoconazole; Electrical measurement; Electrochemical oxidation; Electrode materials; Electrodes; Flow injection analysis; Fungicides; HOMO/LUMO spatial distribution; Oxidation; Pesticides; Quinones; Silver chloride; Spatial distribution; Triazoles; Voltammetry; Water sampling; Voltammetry; Boron doped diamond electrode; Oxidation; Difenoconazole; HOMO/LUMO spatial distribution
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2021.138260

•Unique report on electrooxidation of a pesticide from the triazole group.•Difenoconazole gives voltammetric signal at ca +1.75 V on BDD electrode.•HOMO spatial distribution and atomic charges calculations performed.•Voltammetric and FIA-ED method developed and pesticide interferences excluded.•Recoveries are 92–107% for determination in water and pesticide preparations. Triazole pesticides act as sterol synthesis inhibitors and have been considered as redox-inactive with a variety of electrode materials. In this study, electrochemical oxidation of the fungicide difenoconazole (DFC) was studied in aqueous solutions on oxygen terminated boron doped diamond electrode. It provided a pH-independent irreversible anodic peak at a very positive potential of ca +1.75 V (vs. Ag/AgCl) in acidic media, which could be used for its quantitation in batch voltammetry and flow injection analysis with amperometric detection. The attained detection limits for the determination of DFC in 0.1 mol L−1 HNO3 / phosphate buffer pH 2.0 were 0.049 μmol L−1 for differential pulse voltammetry and 1.58 μmol L−1 for FIA-ED. The former method did not suffer from any significant matrix interferences or interferences of other fungicides and yielded acceptable percentage recovery values (ranging from 96% to 107%) for DFC determination in model river water samples. Similar results comparing both methods at a 95% confidence level were obtained for DFC determination in pesticide preparations. Further, an oxidation mechanism leading to hydroxylated derivative of DFC and subsequent formation of a quinone was suggested. Results were supported with HOMO spatial distribution calculations and atomic charges calculations for arising radical cations. [Display omitted]