Long-lasting copper carbon nanotubes for non-enzymatic electrochemical sensing of glyphosate

Abstract

Accurate electrochemical detection of glyphosate (GLY) presents significant challenges due to its non-electroactive nature on conventional electrode materials. To address this challenge, copper-modified electrodes have been developed to form a complex with GLY, enhancing detection capabilities. In this study, we propose an innovative material: copper-modified carbon nanotubes on a glassy carbon electrode (Cu/CNT/GCE). The detection mechanism of GLY using Cu/CNT/GCE involves the formation of a copper-GLY complex, which inhibits the electrochemical response of copper, proportionally to the GLY concentration. This effect is enhanced by the synergistic interaction between copper and carbon nanotubes, increasing the electrochemical stability and detection capacity of the system. To evaluate the electrochemical performance of Cu/CNT/GCE, cyclic voltammetry was performed at different electrolyte concentrations and pH levels. Square wave voltammetry was employed for the electrochemical quantification of GLY, showing a linear correlation between GLY concentration and the inhibition of the copper response. The proposed sensor exhibited a low limit of detection (0.098 ppm) and a limit of quantification (0.326 ppm). Furthermore, the electrode demonstrated long-term stability, retaining 95 % of its signal after one year of storage. This stability is attributed to the carbon nanotube support, which prevents corrosion of copper particles. Recovery values ranged from 94 to 106 % for Citromax™ and Orium™ glyphosate with precision. The method showed excellent selectivity for GLY detection, even in the presence of other herbicides such as diuron and oryzalin. These properties suggest that Cu/CNT/GCE presents promising features for the electrochemical monitoring of GLY in diverse environmental samples.