Abstract
The performance of two different analytical methodologies to investigate the presence of glyphosate (GLY) and aminomethylphosphonic acid (AMPA) residues in wine samples was evaluated. Transformation of compounds in their fluorene-9-methyloxycarbonyl derivatives permitted their separation under reversed-phase liquid chromatography with tandem mass spectrometry (LC–MS/MS) determination. Although the wine matrix severely impaired the efficiency of GLY derivatization, this drawback was solved using a molecularly imprinted sorbent for the previous, selective extraction of GLY and AMPA from wine. Alternatively, the use of a strong anionic exchange, polyvinyl alcohol-based LC column, turned to be the most effective alternative for direct determination of both compounds in diluted wine samples. The chromatographic behavior of this column and the magnitude of matrix effects observed during analysis of diluted wine samples were significantly affected by the composition of the mobile phase. Under final working conditions, this column permitted the separation of AMPA and the fungicide fosetyl (which shows common transitions in tandem MS/MS methods), it improved significantly the sample throughput versus extraction-derivatization-purification method, and it allowed the use of solvent-based calibration standards. Both analytical procedures provided similar limits of quantification (LOQs) for GLY (0.5–1.0 ng mL−1), while the multistep method was 8 times more sensitive to AMPA than the direct procedure. GLY residues stayed above method LOQs in 70% of the processed wines; however, concentrations measured in 95% of positive samples remained 100 times below the maximum residue limit (MRL) set for GLY in vinification grapes.Graphical abstract
Highlights
Glyphosate (GLY) is worldwide employed as a non-selective weed killer in gardening and agriculture [1]
At the pH value required to carry out the reaction, many compounds present in the wine matrix tend to precipitate (Fig. S1A and S1B), which might compromise the efficiency of the derivatization process
We investigate the suitability of molecularly imprinted polymers (MIP) SPE cartridges to isolate both compounds from wine samples
Summary
Glyphosate (GLY) is worldwide employed as a non-selective weed killer in gardening and agriculture [1]. Other uses which might contribute to introducing GLY in the food chain are the control of herbaceous. The quantification of trace concentrations of GLY and AMPA represents a challenging issue due to the high polar, zwitterion character, low molecular weight, and ligand properties of both species. Derivatization of polar moieties in the structure of both compounds (i.e., using a combination of trifluoroacetic acid and trifluoroethanol [6], or a silylation reagent [7]) allows their determination by gas chromatography-mass spectrometry (GC–MS) [6, 8]. Liquid chromatography-mass spectrometry (LC–MS) remains the most resorted technique for the quantification of GLY and AMPA in environmental and food samples.
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