Electrochemical Detection of the Pesticide Bentazone Using Shadow-Printed Carbon Electrodes

Abstract

Pesticides are intensively used in agriculture to increase yield in food production by protecting crops from damaging organisms or competing plants [1]. Although pesticides have helped us meet the growing food demand, the use of pesticides has led to contamination of water resources from which we obtain our drinking water[2]. Bentazone is one of the widely used pesticides for control of crop quality. The compound is highly soluble in water, very mobile in soil and has a tendency to leach from the field into groundwater and surface water. Consequently, the water resources often have bentazone concentrations above the European regulation limit of 0.1 µg/L (0.39 nM)[3]. Monitoring of bentazone in water resources is obligatory. However, due to the complexity of the manual sampling, transport of samples and the need for centralized laboratories to conduct chromatographic analyses of the water, the monitoring is only conducted a few times a year[4]. This means that high concentrations of bentazone in the water may slip in between the samplings and reach the consumers through the water taps[5]. Here we present a simple electrochemical bentazone detection technique that has the potential of being deployed directly in water wells for the continuous monitoring of the water quality. The technique is based on electrochemical measurements using electrodes shadow-printed on a capton substrate. The electrodes consist of carbon and the resulting sensors have been proven to be robust and generate stable signals for at least 25 measurements[6]. We have used the sensors to achieve the selective detection of bentazone in phosphate buffer as the supporting electrolyte. Square wave voltammetry was used to selectively identify bentazone at 0.77 V. A calibration curve for the compound was obtained in the linear range between 0.190 – 50 µM and with a limit of detection of 0.063 µM at pH 7.0. Several other relevant compounds with chemical structures close to bentazone were tested to determine the risk of signal interference. We could demonstrate that the detection method is selective to bentazone, and other similar compounds did not change the target signal. Furthermore, we have spiked lake water and groundwater with bentazone to test the method on real water samples. It was possible to selectively quantify bentazone in the respective waters, despite any unknown chemicals in the samples. The availability of portable potentiostats offer the possibility of on-site detection of bentazone in the fields[7]. The low-cost shadow-printed sensors allow single-use of the sensors for monitoring water resources. Although the method has still not reached the regulation limit, this study is a proof-of-concept showing the possibility of conducting simple, on-site determination of pesticides in water resources.