Pesticide Testing

Singh, R., and J. Dhalani. Microchemical Journal (2024): 112292.

A high-performance liquid chromatographic (HPLC) method was developed and validated for the simultaneous determination of tolfenpyrad, pyraclostrobin, trifloxystrobin, azoxystrobin, fipronil, thiamethoxam, and thiophanate-methyl in their respective commercially available formulations.

The active ingredients were chromatographically separated from additives and co-formulations using isocratic elution with a 0.1% orthophosphoric acid and acetonitrile mixture (30:70, v/v) at a flow rate of 1.0 mL/min. The separation was performed on an Inertsil ODS-3 column (250 × 4.6 mm, 3.5 µm) with UV detection at 190 nm. The method showed a 20-minute run time, with retention times for thiamethoxam, thiophanate-methyl, azoxystrobin, fipronil, pyraclostrobin, trifloxystrobin, and tolfenpyrad at 2.96, 3.68, 5.98, 8.39, 11.31, 13.74, and 16.38 minutes, respectively. The method was validated in accordance with SANCO guidelines, ensuring precision, linearity, robustness, accuracy, LOD, specificity, and selectivity. This method offers several advantages, including rapid analysis, sustainability, and cost-effectiveness. It can be applied to various sample types, including water and food.

Tutunaru, Bogdan, et al. International Journal of Electrochemical Science 19.5 (2024): 100561.

This study utilized thermal analysis techniques to evaluate the stability of captan pesticide (CPTN). Simultaneous Thermogravimetry (TG), Differential Thermal Analysis (DTA), and Differential Scanning Calorimetry (DSC) were applied to investigate the stability of CPTN over a temperature range of 20 to 600 °C.

The thermal analysis results of CPTN, obtained at a heating rate of 10 °C/min, are shown in Figure (a). The thermogravimetric curve (TG - red), differential thermal analysis (DTA - blue), and differential scanning calorimetry (DSC - green) were recorded. The TG curve indicates that CPTN exhibits relative thermal stability up to about 150 °C. In the temperature range from room temperature to 150 °C, a 3.05% mass decrease is observed, attributed to the removal of water or other physically adsorbed solvents from the sample surface. This process is also identified by the DSC and DTA curves, which show extended endothermic peaks, indicating the release of adsorbed compounds without affecting the chemical stability of captan.

The DSC and DTA curves also highlight a sharp peak at 174.2 °C, corresponding to the melting point of captan. The slight deviation of 3.8 °C from the expected value of 178 °C, along with the relatively broad peak, is due to the overlap with the initiation of a decomposition reaction that begins between 154 °C and 180 °C. These characteristics are further confirmed by the dDSC and dDTA curves (Figure (b)).

Additional studies on the determination of captan at different temperatures using supercritical fluid chromatography coupled with mass spectrometry reported that it cannot be accurately detected at temperatures above 200 °C due to molecular degradation.

Bao, Jing, et al. Sensors and actuators B: Chemical 279 (2019): 95-101.

A biosensor based on a 3D graphene/copper oxide nano-flower platform, with acetylcholinesterase immobilization, was employed for the sensitive detection of organophosphate pesticides. The electrochemical performance of the biosensor was evaluated using cyclic voltammetry, electrochemical impedance spectroscopy, amperometry, and square wave voltammetry.

A schematic representation of the electrochemical 3D graphene/copper oxide nano-flower-based acetylcholinesterase biosensor, modified with a glassy carbon electrode, is shown in the figure. The biosensor, named AChE-CS/3DG-CuO NFs/GCE, exhibited a wide linear dynamic range (LDR) for malathion detection, ranging from 3 pM to 46.67 nM, with a limit of detection (LOD) of 0.92 pM. The biosensor demonstrated good selectivity and stability. When tested with water samples, the recovery rates ranged from 94% to 106%.