Eletrodo descartável de lápis em papel modificados com cobre para a detecção de glifosato em água

Abstract

Glyphosate (Gly) is a powerful herbicide used in Brazil and around the world to control weeds and grasses in both agriculture and landscaping. The indiscriminate use of this substance has raised concerns about the increasing risks regarding the contamination of surface and underground waters, and for human health. In this work, a low-cost disposable electrochemical sensor was developed using pencil as a source of conductive material and paper as substrate for in loco electrochemical detection of Gly in water samples. The electrodes were pencil-drawn on Kraft paper with the aid of a 3D support, and subsequently modified by chronoamperometric electrodeposition of metallic copper, which acts as an analytical recognition agent for Gly by complexation. The electrodeposition parameters of Cu on the disposable electrode were evaluated by cyclic voltammetry considering the cathodic event of Cu(II) to Cu(0). In this case, the best results were obtained with the electrode modified with copper applying a potential of - 0.6 V, electrodeposition time of 80 s and Cu(II) precursor concentration of 0.05 mol L-1 . The pencil-drawn electrode was then used in the detection of Gly, employing a miniaturized 3Dprinted electrochemical cell. Differential pulse voltammetry for different concentrations of the analyte showed linearity fo current reading in the range of 4 to 12 mol L-1 , and sensitivity of 1.16 A/mol L-1 , which are comparable to other works in the literature that develop electrochemical systems for this same application. Using the proposed system, LOD and LOQ of 0.84 µmol L-1 (142.01 µg/L) and 2.8 µmol L-1 (473.39 µg/L) were obtained, respectively, values that are below the concentrations of the Maximum Residue Levels of Gly established by Anvisa (500 µg/L), highlighting the applicability of the proposed system. The sensor also showed selectivity for Gly against the main interferents, and a recovery rate of this analyte in an artesian well water sample between 94 and 103%, demonstrating analytical applicability in real samples. These results highlight the potential of the proposed disposable and low-cost system developed for detecting Gly in water samples.