LC/MS/MS Analysis of Glyphosate and Glufosinate (VT-50 2D)

Organophosphate herbicides such as glyphosate and glufosinate are globally used non-selective weed killer, effective for most weeds. Most countries set regulations for organophosphate herbicides use due to concerns on their toxicity to humans. Therefore, monitoring their concentrations in environment and foods are required.
Those compounds are highly hydrophilic, and thus HPLC is a preferred analysis method. However, they are hardly retained under reversed phase mode. To compromise the problem, methods using pre-column derivatization or addition of ion-pair reagent to the eluent are often applied.
In this application, HILICpak VT-50 2D, a polymer-based HILIC mode column, was used under alkaline condition. The results demonstrated the method’s feasibility for the simultaneous LC/MS/MS analysis of glyphosate, glyfosinate, and their metabolites, as well as ethephon, a plant growth regulator which has similar structure to glyphosate. The method proved to provide 1 ng/mL level quantification of the compounds. The method developed here provides a simple and highly sensitive analysis without the use of derivatization nor use of ion-pair reagent. The pH of the eluent used was about 9, thus the system needs to be alkaline tolerant. The use of alkaline eluent improves the peak shape (less tailing) of glyphosate than using an acidic condition. Note that these phosphorus containing pesticides have tendencies of forming metal coordination compounds, therefore select PEEK materials for the flow-line after the injector wherever it's possible.

Sample : 50 μL
1 ng/mL each

Column       : Shodex HILICpak VT-50 2D (2.0 mm I.D. x 150 mm)
Eluent       : 50 mM NH4HCO3 aq./CH3CN=50/50
Flow rate    : 0.3 mL/min
Detector     : ESI-MS/MS (MRM)
Column temp. : 40 °C

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