Degradation of [¹⁴C]Carfentrazone-ethyl under Aerobic Aquatic Conditions

Abstract

Carfentrazone-ethyl (CF-E) is an aryl triazolinone reduced-risk herbicide for use on corn, wheat, and soybean. As part of the assessment of its metabolic fate, the aerobic aquatic metabolism of [(14)C]CF-E at a concentration of 0.22 microg/g was investigated. Two separate aquatic sediments (silty clay loam and clay loam soils, flooded with water) were used in the study. At each of eight samplings throughout the 30-day study, the distribution of radioactivity between surface water, sediment, and volatile fractions was assessed. At zero time, the majority of the applied radioactivity was contained in the water layer (83-90%), declining to 70-80% after 30 days. This was coupled with an increase in the percent radioactivity in the soil layer from 4-6% at day 0 to 13-19% after 30 days. Nonextractable soil residues and volatile degradation products were formed in negligible amounts. Analysis of the incubation extracts from either aquatic sediment indicated a rapid conversion (<2 days) of the parent CF-E ester to carfentrazone-chloropropionic acid. Over time, increasing amounts of a cascade of acidic degradation products comprising >90% of the applied radioactivity were formed. Identification of these degradation products was initially achieved through chromatographic comparison with reference synthetic standards and subsequently confirmed using LC-MS analysis. A degradation pathway for CF-E under aerobic aquatic conditions is proposed.

Enantioselective separation of the carfentrazone‐ethyl enantiomers in soil, water and wheat by HPLC

“…Carfentrazone‐ethyl,ethyl‐( RS )‐2‐chloro‐3‐[2‐chloro‐5‐(4‐difluoromethyl‐4,5‐dihydro‐3‐methyl‐5‐oxo‐1 H ‐1,2,4‐triazol‐1‐yl)‐4‐fluorophenyl]propionate (Fig. 1), is a relatively novel herbicide produced by FMC (Agricultural Products Group, Philadelphia, PA 19103, USA) 10. It is mainly used on wheat, corn, and soybeans against broadleaf weeds, which is a post‐emergence herbicide used to control weeds by membrane disruption, as a result of inhibition of the enzyme protoporphyrinogen oxidase 11.…”

Sorption–desorption of flucarbazone and propoxycarbazone and their benzenesulfonamide and triazolinone metabolites in two soils

“…The only other published research on processes in soils and water for these chemicals was on flucarbazone dissipation, which was reported to be more rapid in wetter soils with higher organic carbon content 7. There is also little published research on related aryltriazolinone herbicides such as carfentrazone‐ethyl 8, 9…”

Dissipation kinetics and degradation mechanism of amicarbazone in soil revealed by a reliable LC-MS/MS method

“…As critical issues to ensure safe uses, the dissipation kinetics and degradation mechanisms of various triazolinone herbicides in soil, i.e., sulfentrazone and carfentrazone-ethyl have been investigated (Elmarakby et al 2001;Han et al 2007;Martinez et al 2008a, b). With regard to AMZ, only one recently published report has been found to investigate its degradation by photochemical process in aqueous solution under different conditions, such as pH values, dissolved oxygen, and nitrate concentrations (Peixoto and Teixeira 2014).…”