Abstrait

DECAGLIP - Colorimetric Detection of Glyphosate Herbicide

Gabriela C Delela*, Mariana Brunetto Büttenbender

The project addresses the issue of the verification of the presence of pesticide N-(phosphonomethyl) glycine, commonly known as glyphosate, in small amounts through an innovative method of colorimetric detection. The purpose of this project is to find a facilitator of glyphosate residues’ identification in apple samples, which may be used in the inspection of the same. The importance of the research is precisely to detect glyphosate in human consumption, since this pesticide is considered probable carcinogen in humans by IARC (International Agency for Research on Cancer), and its use is growing in an exceptional way in the whole world. The current methods for detection of glyphosate are based in High Performance Liquid Chromatography (HPLC), which is more expensive and complex than the colorimetric analysis. The proposed method involves the formation of glyphosate complexes with copper (II) ions in aqueous media; followed by the colorimetric detection which is based on the enzymatic activity of copper (II) in peroxidase reactions. Copper catalyzes the peroxidase reaction that occurs between the chromogen 3,3,5,5-tetramethylbenzidine (TMB) and H2O2, producing a blue color change in the solution. When copper is complexed with glyphosate, it occurs the inhibition of catalysis and hence lesser intensity of the color produced. Thus, the concentration of glyphosate in solution can be determined by the formation of copper-glyphosate complexes, which prevent the color development. According to the results obtained so far, including the successfully glyphosate extraction from apple samples using the QuEChERS extraction method, it is possible to observe color changes in the solutions distinguished by naked eye and absorbance changes at very low concentrations, up to 1.185 ppm of glyphosate, by the method of UV–visible Molecular Absorption Spectroscopy using 655 nm of wavelength. Therefore, the proposed method shows high sensitivity, besides its simplicity of procedure and immediate response.