New Strategy for Glyphosate, Glufosinate, and AMPA quantification in food: In-vial addition of pairing agent

Introduction

Glyphosate and Glufosinate are phytosanitary products that are commonly used as weed killers, particularly in cereals and vegetable crops. Glyphosate works by blocking the chain of synthesis of amino acid precursors which are essential for the functioning of the plant, especially for photosynthesis. In 2015, the World Health Organization published a report concluding that Glyphosate should now be classified as a probable human carcinogen along with its major metabolite, Aminomethylphosphonic acid (AMPA). The analysis of Glyphosate, Glufosinate, and AMPA is difficult and expensive. Indeed, their hydrophilic and ionic characteristics prevent their analysis in a multi- residue method for monitoring the environment and food. Currently, different analytical techniques are used. Some analysis used derivatization with active reagents such as FMOC, however, this derivatization step complicates their quantification. For this reason, many other solutions, such as Anion exchange, Hydrophilic Interaction Liquid Chromatography (HILIC), porous graphite carbon, and mixedmode columns were used to determine the underivatized Glyphosate and other polar pesticides with LC-MS/MS in food matrixes. However, each of these methods had limited success. This study presents a new analytical approach allowing for the quantification and separation on the reverse phase thanks to the in-vial addition of a pairing agent. Classical ion-pairing technics are known to have certain drawbacks such as reducing sensitivity due to ionization competition, contamination of LC-MS/MS system, and necessity to increase system cleaning. These drawbacks are mainly due to the high quantity of pairing agents used in the mobile phase. This new strategy uses an ion-pairing reagent—but only by in-vial addition. In this way, the quantity used is extremely low, only 125 nmol by injection. Therefore, in these conditions, the advantages of ion pairing are preserved without the disadvantages.

January 13, 2021 GMT