Trimethylation Enhancement using Diazomethane (TrEnDi) Enhances Mass Spectrometry-Based Analysis of Glufosinate and 3-(Methylphosphinico)propionic Acid in Complex Matrices

Abstract

Glufosinate is the second most commonly used herbicide worldwide; it inhibits glutamine synthetase, which results in increased ammonia levels in plants and mammals. Due to their high polarity, low volatility, small size and lack of chromophores and fluorophores, glufosinate and its breakdown product 3-(methylphosphinico) propionic acid (3-MPPA) are difficult to detect at trace levels. Using the chemical derivatization strategy trimethylation enhancement using diazomethane (TrEnDi), glufosinate and 3-MPPA react with diazomethane and tetrafluoroboric acid to become permethylated, thus reducing their polarity and forming a fixed permanent positive charge on the amine group of glufosinate.When using reversed-phase high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS), analyte retention and sensitivity are increased after derivatization, 6.7-fold for glufosinate and 6.3-fold for 3-MPPA. TrEnDi methodology was applied to canola samples from two separate fields sprayed with Liberty®. Prior to derivatization, the analysis showed no signal associated with unmodified glufosinate or 3-MPPA; however, TrEnDi modification resulted in quantifiable signals for both permethylated species.