Degradation studies of quizalofop-p and related compounds in soils using liquid chromatography coupled to low and high resolution mass analyzers

Rosalía López-Ruiz; Roberto Romero-González; José Luis Martínez Vidal; Manuel Fernández-Pérez; Antonia Garrido Frenich

doi:10.1016/j.scitotenv.2017.06.261

Degradation studies of quizalofop-p and related compounds in soils using liquid chromatography coupled to low and high resolution mass analyzers

Sci Total Environ. 2017 Dec 31:607-608:204-213. doi: 10.1016/j.scitotenv.2017.06.261. Epub 2017 Jul 27.

Authors

Rosalía López-Ruiz¹, Roberto Romero-González¹, José Luis Martínez Vidal¹, Manuel Fernández-Pérez¹, Antonia Garrido Frenich²

Affiliations

¹ Department of Chemistry and Physics, Research Centre for Agricultural and Food Biotechnology (BITAL), University of Almería, Agrifood Campus of International Excellence, ceiA3, E-04120 Almería, Spain.
² Department of Chemistry and Physics, Research Centre for Agricultural and Food Biotechnology (BITAL), University of Almería, Agrifood Campus of International Excellence, ceiA3, E-04120 Almería, Spain.. Electronic address: agarrido@ual.es.

PMID: 28692891
DOI: 10.1016/j.scitotenv.2017.06.261

Abstract

A comprehensive degradation study of quizalofop-p, quizalofop-p-ethyl, quizalofop-p-tefuryl and propaquizafop in soil samples have been firstly performed using ultra high performance liquid chromatography coupled to Orbitrap mass spectrometry (UHPLC-Orbitrap-MS). Thus, metabolites or degradation products, such as CHHQ (dihydroxychloroquinoxalin), CHQ (6-chloroquinoxalin-2-ol), PPA ((R)-2-(4-hydroxyphenoxy)propionic acid) and 2,3-dihydroxyquinoxaline were also monitored. An extraction procedure based on QuEChERS procedure was used. Acidified water (0.1M hydrochloric acid) and acidified acetonitrile (1% acetic acid, (v/v)) were used as extraction solvents, and magnesium sulfate and sodium chloride were used as salts. Dispersive solid phase extraction with C₁₈ as sorbent, was needed as a clean-up step. Several commercial products (Panarex®, Master-D® and Dixon®) were used to evaluate the degradation of the target compounds into their metabolites. The concentration of the main active substances (quizalofop-p-tefuryl, quizalofop-p-ethyl and propaquizafop) decreased during the degradation studies, whereas the concentration of quizalofop-p increased. Dissipation rates of half-live of quizalofop-p were also evaluated, and it was observed that this compound is easily degraded, obtaining values lower than 1day. Taking into account that quizalofop-p is the R enantiomer of quizalofop, a chiral separation was performed by liquid chromatography coupled to tandem mass spectrometry, concluding that in samples containing quizalofop-p-tefuryl, there was a 15% contribution from the S enantiomer and a 85% contribution from the R enantiomer. Metabolites such as PPA, CHHQ and CHQ were detected in soil samples after 15days of application commercial product at concentrations between the limits of detection (LOD) and the limits of quantification (LOQ). CHQ and CHHQ were detected at concentrations higher than the LOQ in samples after 50 and 80days of application, with their concentration increasing during this time up to 500%.

Keywords: Degradation study; Enantiomeric separation; Metabolites; Propaquizafop; Quizalofop-p; UHPLC-Orbitrap-MS.