New technique improves detection of glyphosate and AMPA in agricultural systems

Glyphosate (GLY), the active ingredient in Roundup, is the most commonly used herbicide in the world. Despite its widespread use, concerns have been raised about its potential impact on human health and the environment. A new study published in the Journal of the American Society for Mass Spectrometry has developed an innovative technique to improve the detection of glyphosate and its breakdown product, aminomethylphosphonic acid (AMPA), in agricultural systems (1).

GLY and its breakdown product AMPA are non-selective herbicides that are widely used to control weeds in agricultural systems. Although they are effective in controlling weeds, there are growing concerns over the potential dangers that these compounds pose to human and animal health. Studies have suggested that GLY and AMPA exposure may be linked to cancer, developmental abnormalities, and hormonal imbalances. Moreover, GLY and AMPA can accumulate in the environment and may have toxic effects on non-target organisms, such as bees and aquatic life. These potential health risks have prompted calls for stricter regulations on the use of GLY and AMPA in agriculture.

The study was conducted by Jeffrey M. Manthorpe and Jeffrey C. Smith at Carleton University in Ottawa, Canada. The researchers used in situ trimethylation enhancement using diazomethane (iTrEnDi) to derivatize glyphosate and AMPA into permethylated products ([GLY^Tr]⁺ and [AMPA^Tr]⁺, respectively) prior to analysis via high-performance liquid chromatography-mass spectrometry (HPLC–MS).

Glyphosate and AMPA are not easily detectable using standard analytical techniques due to their low proton affinity and poor chromatographic retention. Therefore, researchers use chemical derivatization to enhance their detectability. In this case, the researchers used a technique called in situ trimethylation enhancement using diazomethane (iTrEnDi) to derivatize glyphosate and AMPA into permethylated products. The permethylation process involves adding methyl groups to the analytes, making them more detectable via high-performance liquid chromatography-mass spectrometry (HPLC-MS) analysis. The permethylated products are represented by [GLY^Tr]⁺ and [AMPA^Tr]⁺, respectively.

The use of iTrEnDi resulted in a 12–340-fold increase in HPLC–MS-based sensitivity for [GLY^Tr]⁺ and [AMPA^Tr]⁺, respectively, compared to underivatized counterparts. The derivatized compounds had limits of detection of 0.99 ng/L for [GLY^Tr]⁺ and 1.30 ng/L for [AMPA^Tr]⁺, demonstrating significant sensitivity improvements compared to previously established derivatization techniques.

In addition, the iTrEnDi technique is compatible with the direct derivatization of Roundup formulations, making it a versatile and effective method for the detection of glyphosate and AMPA in complex samples.

As proof of principle, a simple aqueous extraction followed by iTrEnDi enabled the detection of [GLY^Tr]⁺ and [AMPA^Tr]⁺ on the exterior of field-grown soybeans that were sprayed with Roundup. This demonstrates the potential for the iTrEnDi technique to be used for the detection of glyphosate and AMPA in real-world agricultural systems.

Overall, iTrEnDi is a promising new technique for the detection of glyphosate and AMPA in complex samples. Its ability to improve sensitivity and compatibility with Roundup formulations makes it a valuable tool for researchers and regulators looking to assess the potential impact of glyphosate on human health and the environment.

Reference

(1) Rosales, C. A.; Shields, S. W. J.; Aulenback, C. L. J.; Elezi, G.; Wasslen, K. V.; Pallister, P. J.; Faull, K. F.; Manthorpe, J. M.; Smith, J. C. Improved Chromatography and MS-Based Detection of Glyphosate and Aminomethylphosphonic Acid Using iTrEnDi. J. Am. Soc. Mass Spectrom. 2023. DOI: https://doi.org/10.1021/jasms.3c00026