Metabolic fate of the¹⁴C-labeled herbicide clodinafop-propargyl in soil

Abstract

The metabolic fate of (14)C-phenyl-labeled herbicide clodinafop-propargyl (CfP) was studied for 28 days in lab assays using a soil from Germany (Ap horizon, silt loam, and cambisol). Mineralization amounted to 12.40% of applied (14)C after 28 days showing a distinct lag phase until day 7 of incubation. Portions of radioactivity extractable by means of 0.01 M CaCl2 solution (bioavailable fraction) decreased rapidly and were 4.41% after 28 days. Even immediately after application, only 57.31% were extracted with the aqueous solvent. Subsequent extraction using accelerated solvent extraction (ASE; acetonitrile/water 4:1, v/v) released 39.91% of applied (14)C with day 0 and 26.16% with day 28 of incubation from the samples. Non-extractable portions of radioactivity thus, increased with time amounting to 11.99% (day 0) and 65.00% (day 28). A remarkable increase was observed between 14 and 28 days correlating with the distinct increase of mineralization. No correlation was found throughout incubation with general microbial activity as determined by DMSO reduction. Analysis of the CaCl2 and ASE extracts by radio-TLC, radio-HPLC and GC/MS revealed that CfP was rapidly cleaved to free acid clodinafop (Cf), which was further (bio-) transformed; DT50 values (based on radio-TLC detection of the parent compound) were far below 1 day (CfP) and about 7 days (Cf). TLC analysis pointed to 2-(4-hydroxyphenoxy)-propionic acid as further metabolite. Due to fractionation of non-extractable residues, most of the (14)C was associated with fulvic and humic acids, portions in humin fractions and non-humics were moderate and low, respectively. Using a special strategy, which included pre-incubation of the soil with CfP and then mineralization of (14)C-CfP as criterion, a microorganism was isolated from the soil examined. The microorganism grew using CfP as sole carbon source with concomitant evolution of (14)CO2. The bacterium was characterized by growth on commonly used carbon sources and by 16S rDNA sequence analysis. The sequence exhibited high similarity with that of Rhodococcus wratislaviensis (99.56%; DSM 44107, NCIMB 13082).

Quantitative Identification of Biogenic Nonextractable Pesticide Residues in Soil by 14C-Analysis

“…Regarding the presumed formation of biogenic residues from bromoxynil, the methods required, that is, hydrolysis of proteins, purification of resulting AA, and corresponding analysis, were developed using a bacterial culture of Rhodococcus wratislaviensis (Rhw) cultivated in a medium containing  besides sucrose  14 C-glucose as carbon and energy sources. Rhw is a soil bacterium capable to utilize a number of xenobiotics in soil as carbon and energy source . A culture of the soil bacterium Rhw (DSM – 44107; DMSZ, Braunschweig, Germany) was prepared with Difco Czapek Dox (Nordwald, Hamburg, Germany) medium in a 2 mL centrifugation tube and preincubated at 28 °C.…”

“…Rhw is a soil bacterium capable to utilize a number of xenobiotics in soil as carbon and energy source. 19 A culture of the soil bacterium Rhw (DSM − 44107; DMSZ, Braunschweig, Germany) was prepared with Difco Czapek Dox (Nordwald, Hamburg, Germany) medium in a 2 mL centrifugation tube and preincubated at 28 °C. After 1 day of preincubation (during log-phase) 58 KBq 14 C-glucose (28.6 μg) were added to 1 mL of the suspension.…”

Review of advances in the thin layer chromatography of pesticides: 2012–2014

“…The layer was SIL G-25 UV 254 with toluene-ethyl acetate-acetic acid (84:14:3) mobile phase, detection of zones was under 254-nm UV light, and radioactivity on the plates was examined using a Fujifilm/Raytest Bio-Imager BAS-1000 and Berthold radio-TLC 40 scanner (Flexible Format Multisample Counter MSC 2000). [23] Determination of pesticide residues TLC-densitometry was used for the determination of imidacloprid insecticide for a study of its kinetic disappearance from tomatoes. Chopped sample was extracted with acetonitrile, and 10 uL of extract without cleanup was applied to a silica gel F 254 plate (20 £ 20 cm, 0.25-mm thickness) using a 25-uL Hamilton syringe.…”

“…In studies of the metabolism of the herbicide clodinafop-propargyl (CfP) in soil, extraction was carried out using microwave-assisted extraction (MAE) and accelerated solvent extraction (ASE) as well as traditional Soxhlet extraction. [23] Hydrodistillation (HD) and microwave-assisted HD were used to obtain essential oils from Organium onites for evaluation of their antifungal and antibacterial activities. [24] Solid phase extraction (SPE) has been applied for many years for sample extraction and cleanup prior to TLC using a small sorbent cartridge that is conditioned, the sample is added, and elution is carried out with appropriate solutions to wash off impurities and then recover the analytes.…”

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 .…”