Determination of Glyphosate and AMPA in Three Representative Agricultural Austrian Soils with a HPLC-MS/MS Method

Abstract

We developed a novel method to quantify adsorbed glyphosate and AMPA in soils based on an extraction utilizing Na-tetraborate, an SPE clean-up step, and subsequent LC-MS detection. Reversed phase-based separation of glyphosate and AMPA was realized after FMOC-derivatization. The quantification involved external calibration and 1,2–¹³C, ¹⁵N- labeled glyphosate as well as ¹³C, ¹⁵N labeled AMPA as internal standards. The optimum recovery for extraction was obtained with 40 mM Na-tetraborate. The method was applied in three representative soils (Kirchberg, Phyra, and Pixendorf, Austria) where glyphosate was applied by standard agricultural practices. The recovery for glyphosate extracted with 40 mM Na-tetraborate buffer was 93.5% (RSD <2%) for glyphosate at Kirchberg-cambisol; 95.7% (RSD < 2%) at Pixendorf- chernozem and 79.1% (RSD <7%) at Phyra-stagnosol. The corresponding values for AMPA were 92.4% (RSD <2%) at Kirchberg, 98.1% (RSD <2%) at Pixendorf and 69.9% (RSD <4%) at Phyra. The limits of detection for glyphosate were 6.8 μg kg⁻¹(RSD <10%) at Kirchberg, 4.3 μg kg⁻¹ (RSD <10%) at Pixendorf, and 46.5 μg kg⁻¹ (RSD <7%) at Phyra. The limits of detection for AMPA were 26.7 μg kg⁻¹ (RSD <10%) at Kirchberg, 25.2 μg kg⁻¹ (RSD <10%) at Pixendorf, and 120.3 μg kg⁻¹ (RSD <9%) at Phyra. Accordingly, the limits of quantification were 22.7 μg kg⁻¹(RSD <5%) for glyphosate, and 88.9 μg kg⁻¹ (RSD <2%) for AMPA at Kirchberg and respectively 14.4 μg kg⁻¹ (RSD <6%) and 84 μg kg⁻¹ (RSD <5%) at Pixendorf and 13.8 μg kg⁻¹ (RSD <6%) and 87.2 μg kg⁻¹ (RSD <8%) at Phyra. Both substances in the soils were lower than the LOQ before applying the herbicide Roundup. The influence of higher contents of iron oxides, clay, and acidic pH, resulting in a more pronounced adsorption of glyphosate and AMPA in the soils of Phyra and Kirchberg, is demonstrated.

Keywords:

• Glyphosate
• AMPA
• chernozem
• cambisol
• stagnosol
• adsorption
• HPLC
• tandem mass spectrometry

Acknowledgments

The research project “EDISSOC” No.: 100069, GZ BMLFUW-LE.1.3.2/0130-II/1/2006, was financed by Bundesministerium für Land- und Forstwirtschaft, Umwelt und Wasserwirtschaft (BMLFUW), Amt der Niederösterreichischen Landesregierung, Amt der Steiermärkischen Landesregierung, Landwirtschaftliche Fachschulen Tulln, Mistelbach, Pixendorf, Pyhra, and Kirchberg am Walde.