Development and validation of a simplified method for the determination of glyphosate, AMPA and glufosinate in water.

DEMONTE, LUISINA; MICHLIG, NICOLÁS; GARCÍA, SILVIA R.; DE JESÚS, JUAN JOSÉ; BELDOMÉNICO, HORACIO R.; REPETTI, MARÍA ROSA

Santiago de Chile

Workshop; 5th Latin American Pesticide Residue Workshop; 2015

FiNet, Facultad de Agronomía e Ingeniería Forestal (Universidad Católica de Chile).

Glyphosate (N-phosphonomethyl glycine) and other related herbicides (glufosinate) are extendedly used in Argentina associated to the huge proliferation of GMOs based agriculture. Despite the intense use of these pesticides, their residues are poorly evaluated, with consequences on preservation of public health and environmental impact. This is mainly due to its difficult determination at trace levels in complex samples, and the limited sensitivity and robustness of various existing methods. A simplified method for the quantification of glyphosate, its major metabolite aminomethylphosphonic acid (AMPA) and glufosinate at the low ppb level in environmental samples based in FMOC derivatization and UHPLC-MS/MS is presented. The method involves an overnight reaction step followed by L-L partition with dichloromethane, without further concentration of the sample. Sample preparation development assays involved optimization of variables such as sample size, derivatization steps (reagents, reaction time, pH) and cleanup process. We focused also on alternatives to improve analytes identification, confirmation and sensitivity. For the separation of analytes two different C18 columns and mobile phases (H2O:MeOH, H2O:MeCN) using formic acid and ammonium formiate as modifiers were evaluated. Electrospray ionization in modes ESI(+) and ESI(-) were compared. The ionization conditions (capillary and extractor voltages, source and desolvation temperatures and cone and desolvation flows) were optimized using statistical approaches, while cone voltage and fragmentation conditions were optimized through infusion assays. The method was validated according with SANCO/12571/2013 guidelines. Calibration range was 0.04 ? 250 μg/L running solvent and matrix matched curves, that presented adequate linearity (residuals ≤ 20%, r2>0.99). Trueness and precision was evaluated through recovery study at two concentration levels (LOQ and 200 μg/L) obtaining an acceptable range of 85-120 % for all analytes. LOD and LOQ values (μg/L) were 0.2 and 0.6 (glyphosate), 0.1 and 0.2 (AMPA), 0.02 and 0.1 (glufosinate) respectively. Comparatively with other existing approaches, the developed procedure has throughput advantages, such as simpler sample preparation and faster chromatographic analysis. The method was applied to analyze real water samples (n=220) from several regional areas of Santa Fe and Entre Rios. Surface water (rivers, streams, channels) and groundwater were satisfactorily analyzed contributing with relevant data not previously known in the region.