Development Of An Analytical Method For Determination Of Glyphosate, Ampa And Glufosinate In Water Samples By High Performance Liquid Chromatography (HPLC) And Fluorescence Detection

Introduction: one of the main threats to water quality in agricultural areas is pesticide contamination. Glyphosate, currently the most used herbicide in Brazil, may be harmful to natural environments and human health, and thus the constant monitoring of rural areas becomes highly important. Objective: develop an analytical method for determination of Glyphosate, its degradation product AMPA, and Glufosinate (another herbicide) in water samples, by using High Performance Liquid Chromatography with detection by fluorescence (HPLC-FL; Shimadzu®). Methods: the water sample was fortified with the analytes in concentrations of 100 to 1µg/L, then acidified with phosphoric acid (H3PO4) until reaching pH 2, and finally filtered. An aliquot of 50µL was injected into a Hamilton column of ionic exchange (PRP-X100, 10µm, 250x2, 1mm), and kept at 26ºC. The chromatographic separation was obtained through an isocratic elution of the mobile phase: 0.010 M potassium phosphate, at pH 2.1, adjusted with H3PO4, methanol at 4%, flow at 0.5mL per minute. In the post-column reaction box at 33ºC, the analytes were oxidised with calcium hypochlorite followed by complexation with o-phthalaldehyde-2-mercaptoethanol, whose fluorescent product was detected (excitation at 340nm and emission at 455nm). Results: we detected the presence of Glyphosate, AMPA and Glufosinate in the fortified water samples, at concentrations below the established by the Brazilian regulations for potable water (500µg/L). Conclusions: this study represents an important analytical advance for determination of these compounds, although the method would still need to go through validation before implementing its use in laboratory routine. The method constitutes a valuable tool for environmental monitoring of such contaminants in water samples.