Abstract
The quantification of glyphosate (Gly) and its metabolite aminomethylphosphonic acid (AMPA) in food is often impaired by matrix components. Specifically, interaction between the analytes and natural matrix components in food leads to reduced analyte recovery rates. Here, we studied how the addition of ethylenediaminetetraacetic acid (EDTA) impacted the QuPPe recovery rates of Gly and its metabolite in eight mostly problematic matrices using tandem mass spectrometry. QuPPe recovery rates of glyphosate and AMPA could be increased dramatically, e.g., in milk from 29 to 93% and 18 to 93%, respectively. Additionally, isotopically labeled internal standards (IL-ISs) effectively compensated for the losses, resulting in IL-IS-corrected recoveries of ∼100% in all cases. The recovery-suppressing effect of metal cations was confirmed in metal-addition experiments, where Gly was more affected through the addition of calcium ions and AMPA through the addition of iron ions to the sample. Overall, the use of EDTA helped to overcome the most serious challenges in the analysis of Gly and AMPA via the QuPPe method without compromising ion chromatography or mass spectrometric detection of these two as well as of 11 additional anionic analytes also covered by this methods.