Rapid Determination of α-Endosulfan and β-Endosulfan in Formulations and Potatoes by High Performance Liquid Chromatography

Electrocatalysis of Endosulfan Based on Fe3O4: An Experimental and Computational Approach

The present work reports the electrocatalytic oxidation of the organochlorine pesticide endosulfan (EDS) using iron oxide (Fe₃O₄) nanoparticles synthesized from Callistemon viminalis leaf extracts. As a sensor for EDS, Fe₃O₄ was combined with functionalized multiwalled carbon nanotubes (f-MWCNTs) on a glassy carbon electrode (GCE). Cyclic voltammetry, electrochemical impedance spectroscopy, and the differential pulse voltammetry experiment were conducted to investigate the electrochemistry of EDS on the GCE/f-MWCNT/Fe₃O₄ sensor. Based on optimized experimental conditions, the reports of analytical parameters show a limit of detection of 3.3 μM and an effective sensitivity of 0.06464 μA/μM over a range of concentrations from 0.1 to 20 μM. With the proposed method, we were able to demonstrate recoveries between 94 and 110% for EDS determinations in vegetables. Further, a series of computational modeling studies were carried out to better understand the EDS surface adsorption phenomenon on the GCE/f-MWCNT/Fe₃O₄ sensor. The highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy gap (-5.18 eV) computed by density functional theory (DFT) supports the layer-by-layer electrode modification strategy's charge transfer and stability. Finally, transition state modeling was able to predict and confirm the mechanism of endosulfan oxidation.

Spectrophotometric determination of endosulfan using thionin and methylene blue as chromogenic reagents

A simple, selective and sensitive spectrophotometric method is proposed for the determination of widely used organochlorine pesticide endosulfan using thionin and methylene blue as chromogenic reagents. The method is based on the liberation of sulfur dioxide from endosulfan by adding acid reagent and alcoholic potassium hydroxide. The liberated sulfur dioxide is passed through potassium iodate solution and the iodine so liberated bleaches the violet color of thionin and blue color of methylene blue and is measured at 600 nm and 665 nm respectively. This decrease in absorbance is directly proportional to the endosulfan concentration. The Beer's law is obeyed in the range of 0.4-7.0 and 0.2-9.0 microg mL(-1) of endosulfan using thionin and methylene blue as reagents respectively. The molar absorptivity and Sandell's sensitivity were found to be 1.05 x 10(5) and 5.03 x 10(4) L mol(-1) cm(-1), 3.85 x 10(-3) and 8.10 x 10(-3) microg cm(-2) of endosulfan using thionin and methylene blue as reagents respectively. The method has been applied for the determination of endosulfan in water, soil and vegetables.