Determination of the fungicide kresoxim-methyl in grape juices using square-wave voltammetry and a boron-doped diamond electrode

Cloud point method applied to the extraction and preconcentration of thiabendazole pesticide from whole grape juice samples and amperometric detection by HPLC

A cloud point method was developed and applied for the first time to extract and preconcentrate thiabendazole (TBZ) from commercial whole grape juice samples, with determination by high performance liquid chromatography coupled to electrochemical detection (HPLC/EC), using a cathodically pretreated boron-doped diamond electrode (BDD). The best conditions for extraction and preconcentration of TBZ by cloud point extraction (CPE) were performed at pH 6.0, by adding 1 mL of the surfactant Tergitol TMN-6 at 10% (mass-to-mass ratio), without heating (at 27 °C) and ultrasonic stirring time of (20 kHz) for 60 min. The HPLC/EC determination was duly validated in a C8 column, in mobile phase with a 69 : 31 ratio (V/V) of phosphate buffer (pH 7.0):ACN, at a flow rate of 1.2 mL min-1 and electrochemical detection with BDD electrode by applying 1.40 V × Ag/AgCl (3.0 mol L-1). Under these conditions, the procedure showed a preconcentration factor (FC) of 21.7, and limits of detection (LOD) and quantification (LOQ) of 6.64 × 10-9 mol L-1 (or 1.33 μg L-1) and 1.66 × 10-8 mol L-1 (or 3.34 μg L-1), respectively. The method provided a percent recovery of 81% to 98%, with a coefficient of variation between 3% and 15%.

A Review on Recent Advances in the Applications of Boron-Doped Diamond Electrochemical Sensors in Food Analysis

The usage of boron-doped diamond (BDD) material has found to be very attractive in modern electroanalytical methods and received massive consideration as perspective electrochemical sensor due to its outstanding (electro)chemical properties. These generally known facilities include large potential window, low background currents, ability to withstand extreme potentials and strong tendency to resist fouling compared to conventional carbon-based electrodes. As evidence of superiority of this material, couple of reviews describing the overview of various applications of BDD electrodes in the field of analytical and material chemistry has been reported in scientific literature during last decade. However, herein proposed review predominantly focuses on the most recent developments (from 2009 to 2020) dealing with the application of BDD as an advanced and environmental-friendly sensor platform in food analysis. The main method characteristics of analysis of various organic food components with different chemical properties, including additives, flavor and aroma components, phenolic compounds, flavonoids and pesticides in food matrices are described in more details. The importance of BDD surface termination, presence of sp² content and boron doping level on electrochemical sensing is discussed. Apart from this, a special attention is paid to the evaluation of main analytical characteristics of the BDD electrochemical sensor in single- and multi-analyte detection mode in food analysis. The recent achievements in the utilizing of BDD electrodes in amperometric detection coupled to flow injection analysis, batch injection analysis, and high-performance liquid chromatography are also commented. Moreover, actual trends in sample preparation techniques prior to electrochemical sensing in food analysis are referred.

Simultaneous determination of strobilurin fungicides residues in bean samples by HPLC-UV-AD using boron-doped diamond electrode

The aim of this paper was the development of a method for the determination of six strobilurins (fungicides) using boron-doped diamond (BDD) electrode with amperometric detection (AD) homemade coupled to high performance liquid chromatography (HPLC/UV-Vis). HPLC separation of fungicides was performed in a C18 reverse phase column using both UV and AD detectors at 200 mn and 1.9 V, respectively. The linear range for each strobilurin was from 5 to 15 mg L^-1 and the correlation coefficients for all the compounds were above 0.997. Both detectors presented adequate detectability (LOD ranging from 1.33 to 1.57 μg kg^-1) respecting the limits pre-established by regulatory agencies. The method was validated presenting good values of recovery and accuracy. In the spiked samples the recoveries ranged from 61.6% (trifloxystrobin) to 98.8% (azoxystrobin) for UV and 62.3% (trifloxystrobin) to 95.2% (azoxystrobin) for AD. In blanks spikes the recovery varied from 77.8% (picoxystrobin) to 88.4% (kresoxim-methyl) for UV and 76.7% (picoxystrobin) to 87.1% (dimoxystrobin) for AD. The method showed good precision (RSD < 10%). The results obtained by amperometric and UV detections were statistically comparable. Seven bean samples were analyzed to detect fungicide residues.

Kresoxim-methyl and famoxadone as activators of toxigenic potential of Aspergillus carbonarius

Ochratoxin A (OTA) is a secondary metabolite produced by filamentous fungi species belonging to the genera Penicillium and Aspergillus. The contamination of grapes by ochratoxigenic species occurs worldwide in regions of tropical and temperate climates. Better control of fungal growth is achieved through good cultural practice and proper selection of fungicides. Kresoxim-methyl and famoxadone are the most common fungicides used in vineyards. This study aimed at analysing the OTA production and toxigenic potential of Aspergillus carbonarius under fungicide treatment with famoxadone and kresoxim-methyl. The growth rate of A. carbonarius was evaluated by measuring the glucosamine content and the diameter of the fungal colonies. OTA production was quantified by HPLC analysis. The treatment with fungicides, kresoxim-methyl and famoxadone, significantly reduced the fungal growth, by 76% and 60%, respectively. However, the mycotoxin production was greater in the fungicide-treated groups than the control group, showing that even though the fungicides were effective in controlling fungal growth, they were ineffective against mycotoxin production.

Desorption and mobilization of three strobilurin fungicides in three types of soil

Phenamacril (JS399-19 with independent intellectual property developed by China), azoxystrobin, and kresoxim-methyl are strobilurin fungicide. Due to their broad spectrum and good control of most of known fungi, strobilurin fungicide has been widely used in agriculture management. Thus, it is important to evaluate their environmental behaviors particularly in soils and underground water. In this study, the sorption/desorption and mobility of strobilurin fungicides in three Chinese soils (Jiangxi red soil, Taihu paddy soil, and Northeast China black soil) were conducted using comprehensively analytic approaches including batch experiment and soil thin-layer chromatography. The strobilurin fungicides were hard to be adsorbed in Jiangxi red soil but had medium adsorption capability in Tanhu paddy soil and Northeast China black soil, while the desorption of three strobilurin fungicides ranked in the order of Jiangxi red soil > Taihu paddy soil > Northeast China black soil. Soil properties including soil organic matter (SOM), pH, and cationic exchange capacity (CEC) affected the adsorption/desorption of the fungicides. Azoxystrobin and kresoxim-methyl had weak mobility in the soils. JS399-19 was moderately mobile in Jiangxi red soil but was not easily moved in Taihu paddy soil and Northeast China black soil. Due to their weak mobility in soils, these strobilurin fungicides tended to remain in the soil phase but not to shift downward to underground water. As azoxystrobin and JS399-19 had a long retention period in soil, there may become persistent residues in the soil environment.