A simple method for the determination of glyphosate, glufosinate and their metabolites in biological specimen by liquid chromatography/tandem mass spectrometry: an application for forensic toxicology.

ABSTRACT

Glyphosate (GLYP) and glufosinate (GLUF) are phosphorus-containing amino acid type herbicides that are used worldwide. With their rising consumptions, fatal intoxication cases due to these herbicides, whether accidental or intentional, cannot be ignored. Both compounds are difficult to detect, and their pretreatment for instrumental analysis are complicated and time-consuming. Our aim was to develop a simple and rapid quantification method for the two herbicides and their metabolites with liquid chromatography/tandem mass spectrometry (LC/MS/MS). We also compared 2-amino-4-phosphonobutyric acid and DL-2-amino-5-phosphonopentanoic acid as alternative internal standards (IS) to GLYP13C2 15N. Herbicide-containing specimens were highly diluted, evaporated to dryness, and derivatized with acetate/acetic anhydride and trimethyl orthoacetate for 30 min. at 120°C. Our optimized LC conditions successfully separated the target analytes, with acceptable linearities (R 2>0.98) and matrix effects (65%-140%). Accuracy and precision ranged from 80.2 % to 111 %, and from 1.3 % to 13 % at the higher concentration, respectively.The concentration of the herbicides and their metabolites were investigated in a postmortem case of suspected herbicide poisoning cases, in which we detected GLYP and its metabolites. Using one of the three ISs, the GLYP concentrations ranged from 3.1 to 3.5 mg/mL, and 3.3 to 4.5 mg/mL in plasma and urine, respectively; GLYP metabolite concentrations in plasma and urine were 18 to 20 µg/mL and 44 to 54 µg/mL. We thus succeeded in developing a rapid method without extraction for measuring GLYP and GLUF along with their metabolites, and demonstrated its practical applicability.