Metabolic fate of the¹⁴C-labeled herbicide clodinafop-propargyl in a sediment–water system

Abstract

The metabolic fate of (14)C-phenyl-labeled herbicide clodinafop-propargyl ((14)C-CfP) was studied for 28 days in lab assays using a sediment-water system derived from a German location. Mineralization was 5.21% of applied (14)C after 28 days exhibiting a distinct lag phase until day 14 of incubation. Portions of radioactivity remaining in water phases decreased at moderate rate to 18.48% after 28 days; 62.46% were still detected in water after 14 days. Soxhlet extraction of the sediment using acetonitrile released 35.56% of applied (14)C with day 28, while 33.99% remained as non-extractable residues. A remarkable increase of bound (14)C was observed between 14 and 28 days correlating with the distinct increase of mineralization. No correlation was found throughout incubation with microbial activity of the sediment as determined by dimethyl sulfoxide reduction. Dissolved oxygen and pH value of water phases remained almost constant for 28 days. Analyses of Soxhlet extracts of the sediment and ethyl acetate extracts of water phases by radio-TLC and radio-HPLC revealed that CfP was rapidly cleaved to free acid clodinafop (Cf), which was further (bio-) transformed. DT50 values (based on radio-HPLC) were below 1 day (CfP) and slightly above 28 days (Cf). Further metabolites were not detected. Fractionation of humic and non-humic components of the sediment demonstrated that CfP's non-extractable residues were predominantly associated with fulvic acids up to 14 days of incubation (3.36%), whereas after 28 days, the majority of radioactivity was found in the humin/mineral fraction (13.30% of applied (14)C). Due to high-performance size-exclusion chromatography of the fulvic acids fraction derived from assays incubated for 28 days, this portion of (14)C was firmly, possibly covalently bound to fulvic acids and did not consist of CfP or Cf. Using an isolation strategy comprising preincubation of sediment with CfP and mineralization of (14)C-CfP as criterion, a microorganism was isolated from the sediment examined. It grew on (14)C-CfP as sole carbon source with evolution of (14)CO2. The bacterium was characterized by growth on commonly used carbon sources and 16S rDNA sequence analysis. Its sequence exhibited high similarity with that of Nocardioides aromaticivorans strain H-1 (98.85%; DSM 15131, JCM 11674).

A new multiresidue thin layer chromatography–ultraviolet detection method for the rapid determination of six herbicides residue applied as ready mix formulation for rice

“…TLC can easily be used for herbicide residue detection in complex matrices with minimal matrix modification [15, 49, 50]. In order to attain the best separation and reproducibility, it is recommended to always use freshly activated TLC plates and a developing chamber equilibrated with solvent vapor phase.…”

“…This shows that the TLC separation and detection of various pesticide residues can be carried out in the laboratory with appropriate reproducibility that enables the use of the TLC methods for cost-effective screening of a large number of environmental samples, or for the confirmation of the analytes where confirmation of pesticide cannot be done due to unavailability of GC or LC/MS/MS. TLC can easily be used for herbicide residue detection in complex matrices with minimal matrix modification [15,49,50]. In order to attain the best separation and reproducibility, it is recommended to always use freshly activated TLC plates and a developing chamber equilibrated with solvent vapor phase.…”

Perovskite Quantum Dots for Fluorescence Turn-Off Detection of the Clodinafop Pesticide in Food Samples via Liquid–Liquid Microextraction

“…It inhibits the plant growth by disturbing the acetyl coenzyme-A-carboxylase enzyme activity, which is a key biochemical pathway for the synthesis of lipids . Importantly, it exhibits high toxicity toward aquatic living systems. , The survival rate of zebrafish embryos was drastically decreased even at 2 μM clodinafop . In view of this, the maximum residue limits for clodinafop have been regulated by several countries including China, European Union, and US Environmental Protection Agency .…”

“…4 Importantly, it exhibits high toxicity toward aquatic living systems. 5,6 The survival rate of zebrafish embryos was drastically decreased even at 2 μM clodinafop. 7 In view of this, the maximum residue limits for clodinafop have been regulated by several countries including China, European Union, and US Environmental Protection Agency.…”