Phosphate addition enhances alkaline extraction of glyphosate from highly sorptive soils and aquatic sediments

Abstract

BACKGROUND: Analytical constraints complicate environmental monitoring campaigns of the herbicide glyphosate and its major degradation product aminomethylphosphonic acid (AMPA): their strong sorption to soil minerals requires harsh extraction conditions. Coextracted matrix compounds impair downstream analysis and must be removed before analysis. RESULTS:A new extraction method combined with subsequent capillary electrophoresis-mass spectrometry for derivatizationfree analysis of glyphosate and AMPA in soil and sediment was developed and applied to a suite of environmental samples. It was compared to three extraction methods from literature. We show that no extraction medium reaches 100% recovery. The new phosphate-supported alkaline extraction method revealed (1) high recoveries of 70-90% for soils and aquatic sediments, (2) limits of detections below 20 ∼g kg −1 , and (3) a high robustness, because impairing matrix components (trivalent cations and humic acids) were precipitated prior to the analysis. Soil and sediment samples collected around Tübingen, Germany, revealed maximum glyphosate and AMPA residues of 80 and 2100 ∼g kg −1 , respectively, with residues observed along a core of lake sediments. Glyphosate and/or AMPA were found in 40% of arable soils and 57% of aquatic sediment samples. CONCLUSION: In this work, we discuss soil parameters that influence (de)sorption and thus extraction. From our results we conclude that residues of glyphosate in environmental samples are easily underestimated. With its possible high throughput, the method presented here can resolve current limitations in monitoring campaigns of glyphosate by addressing soil and aquatic sediment samples with critical sorption characteristics.

Capturing In Situ Glyphosate (De)sorption Kinetics in Floodplain Aquifer Sediment Columns: Geophysical Measurements and Reactive Transport Modeling

“…The model agrees well with the measured glyphosate profile, increasing from the inlet to the midpoint and dropping sharply after 12 cm. The slight over-prediction of the total sorbed concertation, relative to what was measured, is likely driven by the imperfect recovery (60−90%) of the extraction procedure, 43 hence justifying the systematic discrepancy between modeled and measured profiles. Overall, the measured profile in Col-1, obtained by homogenizing sequential slices of equal length, more closely emulates the shape of the simulated profile.…”

“…Glyphosate was extracted from subsamples (ca. 2 g) of the material collected from Col-1 and the total masses collected in Col-2 . Briefly, a high pH (∼12), phosphate-rich extraction medium (50 mM NaOH and 50 mM Na 2 HPO 4 ) was added to the wet sediment samples to obtain a liquid­[mL]-to-solid­[ g ] ratio of 5:2.…”

“…2 g) of the material collected from Col-1 and the total masses collected in Col-2. 43 Briefly, a high pH (∼12), phosphate-rich extraction medium (50 mM NaOH and 50 mM Na 2 HPO 4 ) was added to the wet sediment samples to obtain a liquid[mL]-to-solid[g] ratio of 5:2. (Note: The total volume of extraction medium added was computed based on the exact mass of the solid sample and the samples' saturated water content.)…”

Heavy rainfall following a summer drought stimulates soil redox dynamics and facilitates rapid and deep translocation of glyphosate in floodplain soils

“…This newly developed method is described in detail elsewhere. 68 To quantitate 13 C 3 , 15 Nglyphosate applied to the eld, non-labelled glyphosate was added to the extraction medium with a nal concentration of 0.5 mg L À1 . Aer centrifugation, the supernatant was acidied with aqueous HCl, precipitates were removed by centrifugation and the remaining supernatant was injected for analysis by capillary electrophoresis-mass spectrometry.…”

Picomolar detection limits for glyphosate by two‐dimensional column‐coupled isotachophoresis/capillary zone electrophoresis‐mass spectrometry

“…This should allow removing phosphate in the first dimension by front-cutting in ITP/CZE. Phosphate is critical since it is widely present in environmental samples but is also used to extract GLP from soils and sediments [50,57]. Aiming at an L-S-L system for the 2D separation, MS-compatible electrolyte components had to be used.…”