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E. Fernandez-Diez, S. Laschober, E. Rosenberg:
"Determination of Glyphosate in Aqueous Samples: Methods, Limitations and Practical Experiences";
Poster: Water Status Monitoring under the WFD Conference, Lille, Frankreich; 14.03.2007 - 17.03.2007.

Glyphosate [N-(phosphonomethyl)glycine] is a broad spectrum, non selective herbicide. Its effect is due to the disruption of some of the plants enzyme systems (non existant in superior animals and humans), which causes inhibition of protein production.

As the European Union has approved strict regulations establishing very low limits of pesticides in drinking water (98/83/EC), very sensitive methods for pesticide residue analysis are needed. There are many multi-residue-methods available for the majority of pesticides but Glyphosate and its metabolites require specific approaches due to their chemical properties such as high ionic character involving high water solubility, low volatility, low mass and lack of chemical groups (e.g., chromophores, fluorophores or substituents with high electron affinity) that support sensitive detection in either liquid or gas chromatography. Different derivatization procedures have been tried to facilitate the analysis of Glyphosate by both gas chromatography (GC) and high performance liquid chromatography (HPLC) systems.

This poster will give an overview of common and successful techniques for the determination of Glyphosate by either HPLC or GC, in most cases using pre- or post column derivatisation.

Reagents typically used for HPLC include: o-phthalaldehyde and N,N-dimethyl-2-mercaptoethylamine hydrochloride solution as well as 9-fluorenylmethyl chloroformate. Detection by UV absorbance, fluorescence or mass spectrometry is then possible.

In GC the standard methods usually applied to pesticides cannot be used due to the polar nature of the Glyphosate; a preceding derivatization step is then required. Most commonly used reactions are esterification using trifluoroacetic acid (TFA), trifluoroacetic anhydride (TFAA) and trimethyl orthoacetate (TMOA) followed by GCMS analysis.

Within the SWIFT-WFD project (funded by DG Research), selected laboratories were invited to analyze a Glyphosate reference material produced by the University of Barcelona. These results are compared to the analyses performed for the assessment of homogeneity and stability which were performed by our group using derivatisation by FMOC-Cl (9-fluorenylmethyl chloroformate) in acetonitrile and HPLC-UV determination.

On the basis of the data submitted, and our own practical experience, the potential and the pitfalls of selected methods will be discussed and recommendations given for the analysis of this pesticide and its metabolites.

References
(1) European Drinking Water Directive 98/83/EC
(2) Stalikas C. D. J. Chromatography A, 907 (2001) 1-19