Validação de metodologia para determinação de glifosato em água por cromatografia iônica com detector de condutividade

Abstract

Brazil is a country that is a big consumer of agrochemicals; according to data from IBAMA, the consumption in the country jumped from 170,000 tons in 2000 to 500,000 tons in 2014, representing a 135% increase over a 15-year period. Among the most commonly used pesticides, glyphosate is in the first place in the sales ranking. Glyphosate is a non-selective, systemic and post-emergent herbicide used to control undesired vegetation in agricultural and non-agricultural sectors. The widespread use of glyphosate causes concern about direct and indirect potential effects on human health and the environment. In 2011, Ministry of Health issued Ordinance No. 2,914 which establishes that the maximum permitted value (VMP) for glyphosate and its main metabolic acid aminomethylphosphonic (AMPA) in water for human consumption is 500 μg / L. The present work aimed to validate the methodology for the determination of glyphosate by ion chromatography using a conductivity detector and to apply the methodology for the determination of glyphosate in treated water samples from small towns in the countryside of the state of Ceará. Metrohm's IC 883 PLUS chromatograph was used with 6.4 mmol / L sodium carbonate solution and 2.0 mmol / L sodium bicarbonate as the eluent. Linearity, selectivity, precision, recovery and limits of detection and quantification parameters were evaluated. The results showed that the method has good linearity (R² = 0.9999) in the concentration range studied as well as good selectivity. The analyte recovery was in the range between 67.333% and 92.050% and the method was accurate, with coefficients of variation between 0.07% and 1.30%. For the detection and quantification limits, 16,049 μg/L and 36,529 μg/L, respectively, were obtained, which demonstrates that the methodology is adequate for the monitoring of the glyphosate residue in water. Among the 108 water samples for water supply, none of them had glyphosate levels higher than the limit of detection and, therefore, they meet the quality and potability parameters of ordinance 2914 of the Ministry of Health.