Determination of Glyphosate and Aminomethylphosphonic Acid in Crops by Capillary Gas Chromatography with Mass-Selective Detection: Collaborative Study

Abstract

A collaborative study was conducted to validate a method for the determination of glyphosate and aminomethylphosphonic acid (AMPA) in crops. The analytes are extracted from crops with water, and the crude extracts are then subjected to a cation exchange cleanup. The analytes are derivatized by the direct addition of the aqueous extract into a mixture of heptafluorobutanol and trifluoroacetic anhydride. The derivatized analytes are quantitated by capillary gas chromatography with mass-selective detection (MSD). The collaborative study involved 13 laboratories located in 5 countries 12 laboratories returned valid data sets. The crops tested were field corn grain, soya forage, and walnut nutmeat at concentrations of 0.050, 0.40, and 2.0 mg/kg. The study used a split-level pair replication scheme with blindly coded laboratory samples. Twelve materials were analyzed, including 1 control and 3 split-level pairs for each matrix, 1 pair at each nominal concentration. For glyphosate, the mean recovery was 91%, the average intralaboratory variance, the repeatability relative standard deviation (RSDr), was 11%, and the interlaboratory variance, the reproducibility relative standard deviation (RSDR), was 16%. For AMPA, the mean recovery was 87%, the RSDr was 16%, and the RSDR was 25% at mg/kg levels.

Analysis of glyphosate and aminomethylphosphonic acid in water, plant materials and soil

“…Analysis of glyphosate and AMPA residues in plant materials first requires an extraction step. Water and acidified water, with shaking or sonication, have been the most commonly used solvents to extract glyphosate and AMPA from diverse plant materials such as watermelon, orange, strawberry, pear, apple, cabbage, cucumber, spinach, potato, tomato, honey, turmeric, chili, coriander, coffee, rice, tea, ginger, coffee senna, hemp sesbania, radish, kidney bean, soybean, soy bean sprouts, soya forage, soy product, corn and corn products, cereal grains, walnut nut meat, tea, Arabidopsis leaves, lilac leaves, grass, quackgrass roots, tree leaves, alfalfa, flowers, shrubs, cattail and vegetable oil (Table ) . Corn, soybean and various forage berry species have also been extracted using water/chloroform, whereas water/methanol (with shaking or sonication) was used for extraction of glyphosate and AMPA from Arabidopsis leaves, maize, peas, barley, flax seed, spinach carrot and straw, and water/acetone (with shaking or sonication) was used to extract wheat and Lolium multiflorum .…”

“…Also, the most commonly used derivatizing reagent has been FMOC‐Cl . Other methods used to derivatize glyphosate and AMPA after extraction from plant material have included: phenylisothiocyanate, 3,6‐dimethoxy‐9‐phenyl‐9 H ‐carbazole‐1‐sulfonyl chloride, 4‐chloro‐3,5‐dinitrobenzotrifluoride, o ‐phthalaldehyde‐2‐mercaptoethanol complex, trimethyl orthoacetate/acetic acid and TFAA with either TFE or HFB . For the few methods that did not use derivatization, analyses were performed using LC‐MS/MS, LC‐UV, CE‐ECL, CE‐MS and an electrochemical biosensor …”

A natural adjuvant shows the ability to improve the effectiveness of glyphosate application

“…After evaporation, the vials were capped and allowed to cool to room temperature (25°C). Using a 250 µL glass syringe, 225 µL ethyl acetate containing 0.2% citral was promptly added and then injected into GC-MS. 30)…”

Evaluation of a Commercially Available Enzyme‐Linked Immunosorbent Assay and a Liquid Chromatography–Tandem Mass Spectrometric Method for the Analysis of Glyphosate in Wheat, Oats, Barley, Malt, and Lentils

“…Most of these involve comprehensive instrumentation, such as liquid chromatography coupled with tandem mass spectrometry (Granby et al 2003;Martins-Júnior et al 2009;Botero-Coy et al 2013) or liquid chromatography with fluorescence detection (Takahashi et al 2001). Comprehensive methods using gas chromatography and mass spectrometry have also been presented (Alferness and Wiebe 2001). Some of these methods use derivatization with polyfluorinated compounds (Alferness and Wiebe 2001) or 9-fluorenylmethyl chloroformate (Schaner 2008;Bernal et al 2012;Botero-Coy et al 2013) to improve the chromatography of glyphosate and AMPA and increase the sensitivity of detection techniques toward these small molecules.…”

“…Comprehensive methods using gas chromatography and mass spectrometry have also been presented (Alferness and Wiebe 2001). Some of these methods use derivatization with polyfluorinated compounds (Alferness and Wiebe 2001) or 9-fluorenylmethyl chloroformate (Schaner 2008;Bernal et al 2012;Botero-Coy et al 2013) to improve the chromatography of glyphosate and AMPA and increase the sensitivity of detection techniques toward these small molecules. Chromatography-based methods that do not use derivatization generally use ion chromatography (Granby et al 2003;Nagatomi et al 2013), although one method reports adequate chromatography with a reverse-phase C 8 column and ammonium carbonate buffer as the mobile phase (Martins-Júnior et al 2009).…”