El-Hallag Ibrahim Shibl, Moharram Youssef Ibrahim, Selim Sameh Mahmoud
Analytical and Electrochemistry Research Unit, Chemistry Department, Faculty of Science, Tanta University, Tanta, 31111, Egypt.
R&D and Microanalysis Laboratories, KZ for Pesticides and Chemicals Company, Nubaria City, Egypt.
Sci Rep. 2023 Aug 31;13(1):14332. doi: 10.1038/s41598-023-41498-3.
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 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 R 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.
开发了一种有效的电分析方法用于对杀螟硫磷农药进行定量评估。通过在其表面施加一层番红来构建电化学修饰的碳糊电极（CPE）。番红单体易于氧化。因此，在pH为6的磷酸盐缓冲液（BPS）的（2×10⁻³ M）番红缓冲溶液中，使用循环伏安法通过电聚合施加一层番红，电位窗口为（-1.6：+2 V），扫描速率为100 mV/s。使用扫描电子显微镜（SEM）图像对修饰电极的形态进行表征。通过观察随着后续扫描循环峰值电流的逐渐增加来表征电聚合过程。这种修饰的CPE电极通过循环伏安法对杀螟硫磷硝基的阴极峰在约-0.73 V处显示出明显的灵敏度，通过增强其灵敏度使其比裸碳糊电极（CPE）高约10倍。电聚合过程的循环次数优化为12次。在此，在-0.73 V处的峰值电流逐渐增强直至12次循环，之后明显下降，然后又略有增加。通过使用线性扫描伏安法（LSV）重复扫描循环来确保修饰电极的重现性，以测定5 μM的杀螟硫磷，发现在开始逐渐下降之前，10次扫描的峰值电流不变。在先前优化的电位窗口（-0.4：-1 V）、扫描速率100 mV/s、pH为6的磷酸盐缓冲液条件下，使用LSV伏安法进行定量研究。在此，使用磷酸盐缓冲液将测定介质的pH从pH 5.5变化到pH 8。观察到最明显的峰值电流出现在pH为6时，然后逐渐降低，直到在pH 8时完全消失。确定杀螟硫磷农药的最佳吸附积累时间为140 s，范围为（20 s - 170 s）。在此，峰值电流随时间逐渐增加直至140 s，然后观察到一个具有恒定响应的平台。所开发的方法显示出优异的线性范围为（1 μM：15 μM），R参数等于0.99906。检测限（LOD）和定量限（LOQ）分别计算为0.1 μM和0.34 μM。计算的回收率、准确度达到了令人满意的水平。重复性和再现性测量的精密度限值均不超过1%。针对8 μM杀螟硫磷的浓度，测量了所建议的LSV方法相对于标准高效液相色谱（HPLC）方法的F值和t值，分别为1.482和0.123，均未超过表格值。针对在（0.01 mM - 0.03 mM）浓度范围内故意改变番红浓度的情况，检查了所建议方法的耐用性。观察到平均回收率在（98.33 - 98.93%）和精密度在（1.39 - 2.6%）方面无显著差异。因此，所开发的LSV方法的可靠性和有效性得以实现，并且被认为是一种可靠的方法。
