Simplified LC-MS/MS Method for Glyphosate, AMPA, and Glufosinate in Oat-Based Cereals

This article from Issue 12 of the Analytix Reporter, produced by Merck, introduces a simplified LC-MS/MS method with interference removal by SPE for the determination of glyphosate, (aminomethyl) phosphonic acid (AMPA), and glufosinate in cereals using a QuPPe method based extraction.

Glyphosate is one of the most used herbicides in the world with more than 0.64 million tons of glyphosate applied to fields per year. This chemical’s
usage increased after the introduction of genetically modified, glyphosate tolerant crops such as corn, soybeans, and cotton. In the USA, US Environmental
Protection Agency (EPA) regulation document Code of Federal Regulations (CFR)-title 40-volume 26 sets the tolerance levels for the occurrence of glyphosate
in food commodities and produce. The EPA tolerance for glyphosate residues in cereal grains (also called crop group 15) are set at 30 ppm; this limit excludes
rice, soy, and corn. In the European Union (EU), maximum residue levels (MRL) in oats are 20 mg/kg for glyphosate and 0.03 mg/kg for glufosinate (lower limit of analytical detection).

In this article, a simplified LC-MS/MS method for the determination of glyphosate, (aminomethyl) phosphonic acid (AMPA), and glufosinate in cereals is described. The method enables the analysis of glyphosate and its metabolites without sample derivatization. The samples are prepared utilizing an extraction method based upon the Quick Polar Pesticides (QuPPe) method and separated by high-performance liquid chromatography with MS detection. A carbon-based chromatography column allowed retention of the analytes while a basic ammonium carbonate buffer and an acetonitrile:water mobile phase system ensured proper ionization under negative ESI conditions. The use of a sensitive Sciex 6500 MS instrument enabled low detection limits of 10 ppb in oat-based samples. In multiple analyzed cereals
levels of glyphosate, AMPA and glufosinate were found to be above the detection limits of the method.

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