Homolytic Scission as the Main Pathway in the Liquid Chromatography/ Electrospray Ionization Quadrupole Time-of-Flight Mass Spectrometry of Mesotrione and its Photoproducts

Abstract

The indirect photochemical degradation of mesotrione induced by humic substances was studied by excitation with a solar light simulator. The disappearance rate constant increased by increasing the concentration of molecular oxygen. Three main byproducts were observed. They all arise from the dissociation of the non-aromatic cycle. Collision-induced dissociation tandem mass spectrometry (CID-MS/MS) of the deprotonated molecule was carried out and the effect of the collision energy as well as the elemental compositions of the products ions was used to propose the chemical structures. The presence in the chemical structure of the SO2-Me moiety permitted several types of homolytic scissions leading to the formation of radical anions.

Metabolic Pathway of Topramezone in Multiple-Resistant Waterhemp (Amaranthus tuberculatus) Differs From Naturally Tolerant Maize

“…The third- and fourth-youngest leaves from waterhemp and maize plants (10–12 cm tall) were treated with 60 × 0.33 μL droplets (20 μL total) of a 1.5 mM topramezone solution, including 0.1% (v/v) Tween 20 as a leaf wetting agent, using a glass syringe. Only the treated leaves were harvested from each plant (48 HAT), extracted and partially purified by SPE chromatography, then analyzed by LC-MS (high resolution) as described in Section “Materials and Methods.” Proposed fragment ions following the loss of –CO ( Bouchoux and Hoppilliard, 1981 ), –SO 2 CH 3 and intramolecular SO 2 elimination ( Chahboune and Sarakha, 2018 ) are supported by previous research investigating the fragmentation of isoxazole and mesotrione, respectively. (A) LC-MS/MS spectrum of hydroxytopramezone-1.…”

“…In the upper pathway shown for loss of water from hydroxytopramezone-1 (Figure 6B ), loss of the pyrazolyl ring and carbonyl group leads to the fragment ion at m/z of 236.038 while the corresponding loss of carbon monoxide [M – CO] − from the isoxazole ring ( Bouchoux and Hoppilliard, 1981 ) leads to the ion at m/z of 208.042. Alternatively, intramolecular sulfur dioxide elimination leads to the fragment ion at m/z of 174.054 (Figure 6B ), which was previously reported when analyzing photochemical degradation products of mesotrione ( Chahboune and Sarakha, 2018 ).…”

Development of Fluorescent Co (II)-Integrated Carbon Dots and Their Application as a Off–On Mesotrione Detection Sensor

“…Consequently, the detection of mesotrione residues by developing sensitive, easy, selective, and cost-effective analytical methods and strategies acquires significance. 14−19 To date, numerous detection methods have been reported for the detection of mesotrione, including liquid chromatography mass spectrometry, 17 solid-phase microextraction, 20 enzyme-linked immunosorbent assay, 21 mass spectrometry, 22,23 high-performance liquid chromatography (HPLC), 23 square wave voltammetry, fluorimmuno assay, spectrophotometric method, diode array detection and cyclic voltammetry, and differential pulse voltammetry. A short comparison of those methods is given in Table S1.…”