Enantioselective separation and degradation of the herbicide dichlorprop methyl in sediment

Abstract

Chiral pesticides currently constitute about 50% of all pesticides dosage used in China, and this ratio is increasing as more complex structures are introduced. Dichlorprop methyl (DCPPM) is a chiral herbicide consisting of a pair of enantiomers. In this study, the enantiomeric separation of DCPPM was investigated by gas chromatography (GC) and high-performance liquid chromatography (HPLC) using chiral stationary phases (CSPs), and its enantiomeric degradation was characterized using a DCPPM-degrading bacterial strain isolated from an activated sludge from a textile-printing wastewater treatment plant. Baseline separation by both GC and HPLC was achieved. Incubation with DCPPM-degrading bacteria in different pH solutions showed that the R enantiomer was preferentially degraded over the S enantiomer of DCPPM. The degradation rate constant decreased with increasing pH in the order of k(pH5) approximately k(pH7) >k(pH9). In comparison, the enantioselectivity as indicated by EF followed the order of pH 7 > pH 9-pH 5.

The Persistence of Deltamethrin in Malaysian Agricultural Soils

“…The indigenous microorganisms in the soil play an important role in the degradation of pesticides. The degradation difference of isomers might be due to selective degradation by soil microorganisms occurring at specific environments (Ma et al 2005). The same trend of degradation of a pesticide (imazapyr) was reported by Wang et al (2005).…”

Chiral Analysis of Pesticides and Drugs of Environmental Concern: Biodegradation and Enantiomeric Fraction

“…Dissipation studies and field-only experiments with no incubation experiments considered were left out [72,149,[156][157][158][159][160][161][162][163][164][165][166][167]. beta-cypermethrin soil laboratory incubation experiments under sterile and non-sterile conditions HPLC-VWD enantioselective degradation of beta-cypermethrin observed; different degradation rates observed for the four beta-cypermethrin isomers; EF variation noticed during the degradation process [143] beta-cypermethrinsoil laboratory incubation experiments under sterile and non-sterile conditions with acidic and alkaline matrices, and with racemic mixture and individual enantiomers HPLC-UV enantioselective degradation of racemic-beta-cypermethrin observed only in non-sterile soils; different degradation rates and half-lives observed for the four beta-cypermethrin isomers; no enantiomeric enrichment observed during degradation of individual enantiomers [144] Regarding the analytical methods used to quantify pesticides' enantiomers during biodegradation, the trend is clear and high-performance liquid chromatography with a diode array detector (HPLC-DAD) [117,122,123,126,128,134,135,140,152] and an ultraviolet detector (UV) [120,129,132,136,138,141,144,146,150,151,155], as well as liquid chromatography tandem-mass spectrometry (LC-MS/MS) [21,...…”

“…Generally, all the studies reported enantioselective biodegradation to some extent in the various matrices considered (for instance, algae cultures, agricultural soil, sediment, water, and vegetables) [127][128][129][130]. Diclofop-methyl exhibited diverse enantioselective behaviors in different biodegradation matrices, with its (-)-enantiomer being degraded faster in soil samples and more slowly in Chinese cabbage samples [128].…”

Abundance and Expression of Enantioselective rdpA and sdpA Dioxygenase Genes during Degradation of the Racemic Herbicide ( R , S )-2-(2,4-Dichlorophenoxy)Propionate in Soil

“…As in the case of other chiral pesticides (6,35), preferential degradation of either the R or the S enantiomer of dichlorprop during microbial degradation has been reported (13,22,26). (R,S)-Dichlorprop enantioselectivity is largely dependent upon the behavior of the microbial community at hand and can be influenced by factors such as pH (3,23), soil type (36), and the environment (e.g., soil, water, or sludge) (4,13,47). The enantioselectivity observed during the microbial transformation of chiral dichlorprop implies that enzymes involved in degradation of this compound are somehow able to differentiate between enantiomers.…”