First electrochemistry of herbicide pethoxamid and its quantification using electroanalytical approach from mixed commercial product

Genotoxic and cytotoxic effects of pethoxamid herbicide on Allium cepa cells and its molecular docking studies to unravel genotoxicity mechanism

Pethoxamid is chloroacetamide herbicide. Pethoxamid is commonly used to kill different weeds in various crops. Pethoxamid can leach in the water and soil and can cause toxic effects to other non-target species. Current study is therefore aimed to perform the investigation of the cytotoxic and genotoxic effects of pethoxamid on Allium cepa cells.The root growth, mitotic index (MI), chromosomal aberrations (CAs), and DNA damage were assessed through root growth inhibition, A. cepa ana-telophase, and alkaline comet assays, respectively. Furthermore, molecular docking was performed to evaluate binding affinity of pethoxamid on DNA and very-long-chain fatty acid (VLCFA) synthases. In root growth inhibition test, onion root length was statistically significantly decreased in a concentration dependent manner. Concentration- and time-dependent decreases in MI were observed, whereas increase in CAs such as disturbed ana-telophase, chromosome laggards, stickiness, anaphase bridges, and DNA damage was caused by the pethoxamid on A. cepa root cells. Molecular docking revealed that pethoxamid binds selectively to GC-rich regions in the minor groove of the DNA structure and showed remarkable binding affinity against all synthases taking part in the sequential biosynthesis of VLCFAs. It was concluded that the pethoxamid-induced genotoxicity and cytotoxicity may be through multiple binding ability of this herbicide with DNA and VLCFA synthases.

A liquid colorimetric chemosensor for ultrasensitive detection of glyphosate residues in vegetables using a metal oxide with intrinsic peroxidase catalytic activity

The control of pesticide residues in food is of increasing importance nowadays due to the over-use and misapplication of herbicides in agricultural production. However, the current colorimetric method for rapid detection of glyphosate still faces many challenges like the low sensitivity and stability. Herein, a simple and ultrasensitive liquid colorimetric chemosensor for glyphosate detection was successfully constructed. Glyphosate pesticide can interact with metallic oxidelike porous Co3O4 nanodisc, and inhibit its inherent peroxidase-mimicking activity, making the colour of the solution change from blue to light blue or even colourless. The colour variation of the colorimetric chemosensor enables us to easily distinguish in less than 20 min even by the naked eye whether glyphosate exceeds the allowable level. The limit of detection (LOD) of the chemosensor for glyphosate was calculated as low as 2.37 μg·L-1, and the chemosensor displays excellent selectivity against other competitive pesticides and metal ions. Further studies have also validated the applicability of the colorimetric chemosensor in actual samples like tomato, cucumber and cabbage, indicating that the proposed strategy may have promising application prospects for detecting glyphosate residues in agricultural products.

A novel sensor based on WO3·0.33H2O nanorods modified electrode for the detection and degradation of herbicide, carbendazim

In the present-day scenario, it is necessary to establish more flexible, effective and selective analytical methods that are easy to operate and less expensive. Cyclic voltammetry (CV) can be a useful technique to assess minute quantity of pollutants and in this work, an effort has been made to detect the trace quantification from the environmental samples. Herein, electrochemical sensor was fabricated using tungsten oxide nanorod (WO₃·0.33H₂O) for sensitive detection of fungicide, carbendazim (CBZ). Under optimal conditions, while studying the effect of pH on peak current, the highest peak current was observed at pH 4.2. The degradation of CBZ followed the mixed diffusion-adsorption controlled and quasi-reversible processess at the WO₃·0.33H₂O/GC electrode surface. Using WO₃·0.33H₂O/GCE sensor in SWV provided the lowest limit of detection (LOD) and limit of quantification (LOQ) values of 2.21 × 10^-8 M and 7.37 × 10^-8 M, respectively over the concentration ranges of 1.0 × 10^-7 M to 2.5 × 10^-4 M. The proposed method demonstrates potential applicability of the fabricated sensor for soil and water samples analysis in the management of creating a benign environment.

Examination of degradation and ecotoxicology of pethoxamid and metazachlor after chlorine dioxide treatment

Chlorine dioxide has been reported as very efficiently removing pesticides and other organic compounds from water matrixes. Due to pesticide toxicity and potential toxicity of their degradation products, it is important to monitor these compounds as environmental pollutants in ground and surface waters. Evaluating the effects of chlorine dioxide treatment is necessary, and toxicity studies are used to ascertain the severity of effects of intermediates due to incomplete degradation of the parent compounds. In this paper, for the first time, chlorine dioxide is applied and evaluated for the removal of chloroacetamide herbicides (pethoxamid and metazachlor) from waters (deionized water and Sava River water). The degradation degree of herbicides was measured by high-performance liquid chromatography, the main degradation products were identified using gas chromatography with a triple quadrupole mass detector, and the degree of mineralization was monitored by total organic carbon analysis. Four and two degradation products were identified after pethoxamid and metazachlor degradation, respectively. Total organic carbon analysis showed mineralization occurred, but it was incomplete. The mineralization and the characteristics of the degradation products obtained were tested using Daphnia magna and showed lower toxicity than the parent herbicides. The advantage of the applied treatment was a very high degradation percentage for pethoxamid removal from deionized water and Sava River water (100% and 97%, respectively), with higher mineralization efficiency (65%) than metazachlor. Slightly lower degradation efficiency in the Sava River water was due to chlorine dioxide oxidizing the herbicides and dissolved organic matter simultaneously.

Analytical methods to analyze pesticides and herbicides

Presented in this paper is an annual review of literatures published in 2018 on topics relating to analytical methods for pesticides and herbicides. According to the different techniques, this review is divided into six sections, including extraction methods; chromatographic or mass spectrometric techniques; electrochemical techniques; spectrophotometric techniques; chemiluminescence and fluorescence methods; and biochemical assays. PRACTITIONER POINTS: Totally 134 relevant research articles are summarized. The review is divided into six parts according to the techniques. Chromatographic and mass spectrometric methods are the most widely used.