ABSTRACT
BACKGROUND: The aim of this work is the detection and quantification of bioaccumulated thiamethoxam (THM) in Zea mays at a silver electrode using square-wave voltammetry. Thiamethoxam bioaccumulation and plant development were followed for 10 days from germination to seedling growth. Germination rate, accumulation rate, root length, and plant length were used as indicators. All experiments were carried out using several concentrations of THM (5.0 × 10-4 , 1.0 × 10-3 , 5.0 × 10-3 , 3.4 × 10-2 and 5.0 × 10-2 mol L-1 ). RESULTS: The results confirm that Zea mays was sensitive to this insecticide and that germination and growth inhibition were dose dependent. The efficiency and utility of the proposed method were discussed. The current intensity increases linearly with an increase in the THM bioaccumulated in Zea mays. After 10 days,the recovery results of the extraction of THM from zea Mayes samples spiked with different concentrations were encouraging. The detection and quantification limits were found to be 9.58 × 10-6 mol L-1 (3*SD/B) and 3.13 × 10-5 mol L-1 (10*SD/B). The precision was 2.67% for eight repetitions in a solution of 3.5 × 10-4 mol L-1 THM. Histological tests were also performed to confirm the effect of THM on the plant and showed that exposure to THM induced a net histological modification in the primary root tissue of Zea mays. CONCLUSION: The use of THM can affect the quality of the plant crop yield, and its accumulation in edible plants could pose a potential risk for human and animal health if the insecticide intake were to exceed the recommended tolerable limits. © 2019 Society of Chemical Industry.
Subject(s)
Electrochemical Techniques , Insecticides/pharmacology , Silver/chemistry , Thiamethoxam/pharmacology , Zea mays/drug effects , Electrodes , Germination/drug effects , Insecticides/analysis , Plant Development/drug effects , Plant Leaves/chemistry , Plant Leaves/drug effects , Plant Roots/chemistry , Plant Roots/drug effects , Plant Stems/chemistry , Plant Stems/drug effects , Seedlings/chemistry , Seedlings/drug effects , Seeds/chemistry , Seeds/drug effects , Thiamethoxam/analysis , Zea mays/chemistryABSTRACT
BACKGROUND: Thiamethoxam (3-[(2-chloro-5-thiazolyl)methyl]tetrahydro-5-methyl-N-nitro-4H-1,3,5-oxadiazin-4-imine) belongs to a relatively new class of insecticides known as neonicotinoids, which can block irreversibly nicotinic acetylcholine receptors of the nervous system of insects. Its determination at trace levels is an acute analytical problem. Therefore, chromatography, spectroscopy, and electrochemical technics were reported. These last have several advantages (simple sensitive and less expensive). This work investigated the electro-reduction of Thiamethoxam using simple and rapid method in real samples using metallic silver electrode. RESULTS: Silver particles, known as effective catalysts in the reduction of nitro groups, were studied to explore their roles in the shift of thiamethoxam peak potential. Cyclic voltammetry, Tafel plot and electrochemical impedance spectroscopy analysis suggest that metallic silver electrodes have a significantly greater electrocatalytic activity in thiamethoxam electroreduction than glassy carbon electrodes and carbon paste electrodes. The electrocatalytic activity of metallic silver electrodes in thiamethoxam reduction was investigated by cyclic voltammetry and chronoamperometry. A linear variation in cathodic current with the square root of the scan rate was observed, suggesting that the process is diffusion controlled. Several supporting electrolytes were tested, and the best results were obtained with Britton-Robinson (BR) buffer, pH 10.4. A linear relationship between peak current and concentration was found in the range from 1.0 × 10-5 to 1.0 × 10-4 mol L-1 using square wave voltammetry (SWV) with a correlation coefficient of 0.994. The detection limit and quantification limit were 5.49 × 10-6 and 1.83 × 10-5 mol L-1 , respectively. CONCLUSION: Silve metallic electrode exhibits efficient catalytic activity towards the Thiamethoxam reduction. The proposed electrode was then used for the determination of thiamethoxam in tomato anad orage juice samples. © 2019 Society of Chemical Industry.
Subject(s)
Citrus sinensis/chemistry , Electrochemical Techniques/methods , Insecticides/chemistry , Solanum lycopersicum/chemistry , Thiamethoxam/chemistry , Catalysis , Electrochemical Techniques/instrumentation , Electrodes , Electrolytes/chemistry , Food Contamination/analysis , Fruit and Vegetable Juices/analysis , Limit of Detection , Neonicotinoids/chemistry , Silver/chemistryABSTRACT
Carbon paste electrodes (CPEs) modified with silver particles present an interesting tool in the determination of paraquat (PQ) using square wave voltammetry. Metallic silver particle deposits have been obtained via electrochemical deposition in acidic media using cyclic voltammetry. Scanning electron microscopy and X-ray diffraction measurements show that the silver particles are deposited onto carbon surfaces in aggregate form. The response of PQ with modified electrode (Ag-CPE) related to Ag/CP loading, preconcentration time, and measuring solution pH was investigated. The result shows that the increase in the two cathodic peak currents (Peak 1 and Peak 2), under optimized conditions, was linear with the increase in PQ concentration in the range 1.0 × 10-7 mol/L to 1.0 × 10-3 mol/L. The detection limit and quantification limit were 2.01 × 10-8 mol/L and 6.073 × 10-8 mol/L, respectively for Peak 1. The precision expressed as relative standard deviation for the concentration level 1.0 × 10-5 mol/L (n = 8) was found to be 1.45%. The methodology was satisfactorily applied for the determination of PQ in citric fruit cultures.
