Determination of Quizalofop (DPX-79376) Residues in Hemp Cannabis Matrices by LC-MS/MS

Abstract In this paper, we present the development and application of an analytical method for the determination of residues of the systemic, post-emergence herbicide quizalofop-P-ethyl (a.k.a. quizalofop or DPX-79376) and its metabolite quizalofop acid in hemp cannabis matrices via LC-MS/MS. This method was then applied to measure incurred residues of both analytes in samples of hemp grown in the field according to commercial best practices. A total of nine crop matrices were tested: whole seed, fiber, flower buds, hemp hearts, hemp seed oil, hemp meal, hemp flour, ethanol-extracted CBD resin (CBD-E), and supercritical CO2-extracted CBD resin (CBD-C). Processing of the CBD-E and CBD-C crop fractions was carried out in-house. Field sample analysis utilized sequential extractions, stacked solid phase extraction (SPE) column cleanups, conjugate conversion via enzymatic hydrolysis, and evaporation to prepare samples for LC-MS/MS quantitation. Method validations for each fraction were carried out using untreated hemp matrices over a minimum of three levels, with a lowest level of method validation (LLMV) of 0.050 µg/g. Quizalofop-treated samples from ten field sites across viable production regions were collected and analyzed to determine the quizalofop-P-ethyl and quizalofop acid residues within the different hemp matrices. This data was generated in support of nationwide registration with the United States Environmental Protection Agency (USEPA).