Zsigmond Papp

Bismuth Modified Carbon-Based Electrodes for the Determination of Selected Neonicotinoid Insecticides

Two types of bismuth modified electrodes, a bismuth-film modified glassy carbon (BiF-GCE) and a bismuth bulk modified carbon paste, were applied for the determination of selected nitroguanidine neonicotinoid insecticides. The method based on an ex situ prepared BiF-GCE operated in the differential pulse voltammetric (DPV) mode was applied to determine clothianidin in the concentration range from 2.5 to 23 μg cm−3 with a relative standard deviation (RSD) not exceeding 1.5%. The tricresyl phosphate-based carbon paste electrodes (TCP-CPEs), bulk modified with 5 and 20 w/w% of bismuth, showed a different analytical performance in the determination of imidacloprid, regarding the peak shape, potential window, and noise level. The TCP-CPE with 5% Bi was advantageous, and the developed DPV method based on it allowed the determination in the concentration range from 1.7 to 60 μg cm−3 with an RSD of 2.4%. To get a deeper insight into the morphology of the bismuth-based sensor surfaces, scanning electron microscopic measurements were performed of both the surface film and the bulk modified electrodes.

Voltammetric determination of the herbicide Linuron using a tricresyl phosphate-based carbon paste electrode.

This paper summarises the results of voltammetric studies on the herbicide 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (Linuron), using a carbon paste electrode containing tricresyl phosphate (TCP-CPE) as liquid binder. The principal experimental conditions, such as the pH effect, investigated in Britton-Robinson buffer solutions (pH 2.0–7.0), the peak characteristics for the analyte of interest, or instrumental parameters for the differential pulse voltammetric mode were optimized for the method. As found out, the best electroanalytical performance of the TCP-CPE was achieved at pH 2.0, whereby the oxidation peak of Linuron appeared at ca. +1.3 V vs. SCE. The analytical procedure developed offers good linearity in the concentration range of 1.25–44.20 μg mL−1 (1.77 × 10−4–5.05 × 10−6 mol L−1), showing—for the first time—the applicability of the TCP-CPE for anodic oxidations in direct voltammetry (without accumulation). The method was then verified by determining Linuron in a spiked river water sample and a commercial formulation and the results obtained agreed well with those obtained by the reference HPLC/UV determination.

Electroanalysis of Insecticides at Carbon Paste Electrodes with Particular Emphasis on Selected Neonicotinoid Derivatives

1.1 Recent trends in the use of insecticides Insecticides are substances from the group of pesticides intended for preventing, destroying, repelling or mitigating insects (Pesticide, 2011). Although there are benefits to the use of insecticides, there are also drawbacks, such as potential toxicity to humans and other animals. Residues in fruit and vegetables, cereals, processed baby food and foodstuffs of animal origin are controlled through a system of statutory maximum residue limits (MRLs) (Tuzimski, 2011). The increasing use of pesticides, especially herbicides and insecticides, in agriculture, forestry, and domestic activities for controlling pests causes pollution of the water resources, environment, as well as of many food stuff. The leaching run-off from agricultural and forest lands; deposition from aerial applications and residua from the industrial wastewater treatment are mainly responsible for the water contamination (Gupta, 2004). The pesticides form a strong class of water and environment pollutants, as they are sometimes non biodegradable. The toxicity of pesticides and their degradation products make these chemical substances potentially hazardous contaminants of the environment (Schultz et al., 2003). According to the Stockholm Convention on Persistent Organic Pollutants, nine of the dozen of the most harmful and persistent organic chemicals are pesticides (Ridding the World of POPs: A guide to the Stockholm Convention on Persistent Organic Pollutants, 2005; Pesticide, 2011). The insecticides can be grouped by means of sorting into chemical families. Major insecticide families include organochlorines, organophosphates, carbamates, and neonicotinoids. Organochlorine hydrocarbons (e.g. DDT) could be separated into dichlorodiphenylethanes, cyclodiene compounds, and other related compounds. They operate by disrupting the sodium/potassium balance of the nerve fiber, forcing the nerve to transmit continuously. Their toxicities vary greatly, but they have been phased out because of their persistence and potential to bioaccumulate (Kamrin, 1997). For instance, due to