ORIGINAL ABSTRACT

In large-scale production of corn for feed and food, glyphosate and glufosinate are the most commonly used herbicides for weed control. However, their excessive use has led to severe environmental and health damage. In Mexico and several other countries, the detrimental impact of the overuse of these herbicides has gained social, ecological, and political significance. Therefore, we validated and applied an ultra-high performance liquid chromatographic-tandem mass spectrometry method (UHPLC-MS/MS), based on a derivatization with fluorenylmethyloxycarbonyl chloride (FMOC-Cl) for the simultaneous quantification of glyphosate, aminomethylphosphonic acid (AMPA), and glufosinate. The proposed method demonstrates a linear range of 0.04 to 6.0 mg kg-1, detection limits (LOD) of 15, 21, and 9 µg kg-1, and quantification limits (LOQ) of 45, 63, and 28 µg kg-1 for glyphosate, AMPA, and glufosinate, respectively. Precision under repeatability and reproducibility conditions (coefficients of variation) was ≤ 20%, and recovery percentages for all analytes were 70% to 120%. The developed method is precise and accurate, allowing for satisfactory quantification of the Maximum Residue Limits (MRL) permitted for these analytes in corn grains (1-5 mg kg-1) by international government agencies. Finally, the method was applied to real corn tortilla samples without any matrix detrimental effect. Hence, this methodology can be used for routine national monitoring of corn grain and derived products such as tortillas, totopos, and tostadas, which are highly consumed in Mexico and other Latin American countries.