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This work investigates the validation of the SW-ASV method for the determination of malathion organophosphorus pesticide based on an electrochemically modified (CPE) carbon paste electrode with copper metal. The surface of the modified CPE was constructed by electrodepositing the copper layer at the accumulation step in 1-mM CuSO4.5H2O, PBS at pH 6.6, E accumulation: − 0.8 V, and Taccumulation 240 s. The determining step was performed by adding different concentrations of malathion pesticide and applying the potential toward more positive potential at (− 0.8–+ 1.4 V) to enhance the oxidation of Cu0 metal. It was noticed that the malathion concentration gradient enhances the oxidation peak current of copper at + 0.03 V gradually. SW-ASV method validation was performed at a linearity range confined in (1–10 µM). An analytical curve was constructed and R2 was equal to 0.99995 with good fitted linear relationship. LOD and LOQ were calculated to be 0.0247 and 0.08236 µM, respectively. ANOVA for two sets of measurements using the standard gas chromatographic method and the suggested SW-ASV method was demonstrated via the calculations of F-value and t-value. F and t-values were calculated to be 1.698 and 0.289, respectively, which did not exceed the tabulated F and t-values resulting in the great similarity of results and ensuring the reliability of the suggested test method. This valid SW-ASV method was used to perform the routine analysis of the 95% technical grade and the pesticide formulation 57% emulsion concentrate of the malathion. Valid results were achieved with satisfactory limits of accuracy and precision. [ABSTRACT FROM AUTHOR]

An effective electroanalytical method was developed for the quantitative evaluation of fenitrothion pesticide. The electrochemically modified carbon paste electrode CPE was constructed by applying a safranine layer on its surface. Safranine monomer is easily oxidized. So, a safranine layer was applied via electropolymerization using cyclic voltammetry in (2 × 10–5 M) safranine buffered solution with phosphate buffer BPS at pH.6, potential window (− 1.6: + 2 V), scan rate 100 mV/s. The morphology of the modified electrode was characterized using SEM images. The electropolymerization process was characterized by observing the gradual increases of the peak current with the subsequent scanning cycles. This modified CPE electrode showed an obvious sensitivity by cyclic voltammetry towards the cathodic peak of the fenitrothion nitro group at approximately − 0.73V with good sensitivity by enhancing it to be approximately 10 times more sensitive than on a bare carbon paste electrode CPE. The number of cycles was optimized for the electropolymerization process to be 12 cycles. Where, the peak current at − 0.73 V was gradually enhanced until 12 cycles when it is obviously decreased before slightly increasing again. The reproducibility of the modified electrode was ensured by repeating the sweep cycles using LSV for determining the fenitrothion at 5 µM where it was found that the peak current was unchanged for 10 sweeps before it starts to drop gradually. LSV voltammetry at previously optimized conditions of the potential window (− 0.4: − 1 V), sweep rate 100 mV/s, phosphate buffer at pH.6 was used for the quantitative studies. Where, the pHs of the determining medium were varied from pH 5.5 to pH 8 using phosphate buffer. It was observed that the most identified peak current was at pH.6 which is then decreased gradually until it completely disappeared at pH 8. The optimal accumulation time by adsorption of 140 s for the fenitrothion pesticide was confirmed in the range of (20 s–170 s). Where, the peak current was increased gradually with time up to 140 s then a plateau with a constant response was observed. The developed method showed an excellent linearity range of (1 μM:15 μM) with R2 parameter equal to 0.99906. LOD and LOQ were calculated to be 0.1 μM, and 0.34 μM respectively. Satisfactory levels have been reached for the calculated recovery, accuracy. Precision limits not exceed 1% for both repeatability and reproducibility measurements. F-value and t-value were measured for the suggested LSV method versus the standard HPLC method for the concentration of 8 μM fenitrothion and were found to be 1.482 and 0.123, respectively which didn't exceed the tabulated values. The ruggedness of the suggested method was examined toward deliberate safranine concentration variations in the concentration range of (0.01 mM–0.03 mM). Insignificant differences for the mean recovery at (98.33–98.93%) and precision at (1.39–2.6%) were observed. Hence, the reliability and validity of the developed LSV method were achieved and it was considered as rigid method. [ABSTRACT FROM AUTHOR]

Generic products are not identical to their branded equivalents. They are typically off-patent. Therefore, this paper suggests a selective, reliable, and accurate electrochemical method for quantifying the original and generic glyphosate from Monsanto Roundup®—USA and Rotam Agrochemicals—Hong Kong. The reliability of the suggested electroanalytical method was assured. An electrochemically modified carbon paste electrode was used as a working electrode. This working electrode was constructed by depositing a copper layer electrochemically using chronoamperometry under continuous stirring. The copper deposition was conducted for 180 s at the potential of –0.8 V from an aqueous solution of copper sulphate pentahydrate at pH 6.5. Adjust by adding phosphate buffer. Cyclic voltammograms for electrochemically modified CPE versus Ag/AgCl were recorded between (–0.8...–1.4 V) at a scan rate of 0.1 V s–1 in solutions with and without glyphosate. The results showed an enhancing in the oxidation peak current of the copper previously deposited on CPE by the addition of glyphosate. This enhancing in copper oxidation peak may be attributed to glyphosate adsorption on the surface of the electrode and formation of a complex. SW-ASV method was used as an efficient electroanalytical technique for glyphosate quantification. The operating parameters such as accumulation potential and accumulation time were optimized to give maximum oxidation peak current of copper. Calibration curves were constructed in a concentration range (2 × 10–6–2 × 10–4 mol L–1) for generic, original and standard glyphosate. Calibration curve method was adopted in a comparison. It was observed that there are very minor differences in the slopes of generic, original, and standard glyphosate (0.2982–0.2993–0.2957 μA/μM) respectively. [ABSTRACT FROM AUTHOR]