The stereoselective degradation of indoxacarb enriched with (+)-S-indoxacarb (S/R:70/30) was investigated in three typical green teas. A convenient and precise chiral method was developed and validated for measuring indoxacarb enantiomers in green tea. The developed method was based on high-performance liquid chromatography coupled with tandem mass spectrometry using a Chiralpak IC column. The stereoselective degradation of indoxacarb enantiomers showed that the (+)-S-enantiomer dissipated faster than the (-)-R-enantiomer in all three typical tea farms. However, no enantiomerization was observed after applying pure (+)-S-indoxacarb. Residues on tea plant of the active ingredient (+)-S-indoxacarb from suspension concentrate (SC) was more persistent than that from emulsifiable concentrate (EC).
The degradation modes and characteristics of different pesticides were introduced. In addition, this paper also describes the degradation mechanism of different pesticides, classifies, and summarizes the methods of degradation products identification. For the sake of human life health and better biological environment, we should have a familiar knowledge of the natural degradation of pesticides and understand the photo-hydrolysis and its influencing factors (temperature, pH, light, etc.). Through the degradation mechanism and influencing factors, the degradation time could be accelerated and it also provides a theoretical basis and basic support for the treatment of pesticide residues in the future.
γ-Valerolactone (GVL) is a renowned starting material in production of bio-fuels, valuable chemicals and polymers. The one-pot tandem synthesis of GVL from furfural without a cumbersome intermediate separation/purification process is highly desired, yet the transformation remains challenging owing to the complicated reaction routes. Zirconium phosphate (ZrPO), a cheap and easily prepared solid catalyst with Lewis-Brønsted dual acidity, is herein discovered to enable one-pot tandem transformation of furfural into GVL with using 2-propanol as H-donor/solvent to proceed smoothly. In addition, ZrPO prepared by hydrothermal method exhibits superior catalytic performance in comparison with the counterpart prepared by co-precipitation method, giving a 42.7% yield of GVL at 180 °C. The difference in catalytic activity between ZrPO materials prepared by hydrothermal method and co-precipitation method is linked with their morphology and acid sites density. Furthermore, the as-prepared ZrPO catalyst works in a heterogeneous manner and can be reused for multiple times without significant deactivation.
Hydrolysis
degradation kinetics of vanisulfane in water was investigated
in detail under exogenous substances conditions. The experimental
results indicated that the degradation rate of vanisulfane in aqueous
solution increases with the increase of concentration of Cu
2+
. The degradation of vanisulfane did not change significantly in
Ni
2+
, Zn
2+
, Pb
2+
, and Fe
3+
aqueous solutions. Surfactants have no significant effect on the
degradation of vanisulfane, and the degradation rate of vanisulfane
increases with increasing concentration of fulvic acid. In addition,
the photolysis products were identified by ultra-high-performance
liquid chromatography coupled with Orbitrap high-resolution mass spectrometry.
Five photolysis products were identified, and the degradation reaction
pathway and the mechanism of vanisulfane were proposed, which mainly
involved cleavage of thioether, back into aldehyde, cleavage of ether
bond, demethylation, and intramolecular dehydration processes. This
research on vanisulfane can be helpful for its security evaluation
and increased understanding of vanisulfane in water environments.
A Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS)
pretreatment
technique combined with HPLC–MS/MS was established to detect
26 pesticides in traditional Chinese medicinal leeches. The sample
was extracted by acetonitrile solution with sodium acetate-0.1% (v/v)
acetic acid as a buffer system, then cleaned up by a mixture of 750
mg of MgSO4, 150 mg of C18, and 150 mg of PSA,
separated by an ACQUITY BEH C18 column, and determined
in the dynamic multiple reaction mode. Under the optimized conditions,
the peak areas of the 26 pesticides in leeches showed good linearity
(r > 0.99) between their mass concentrations from
1 to 100 μg/L. At the spike levels of 10, 20, and 100 μg/kg,
the recoveries of 26 pesticides in leeches were 72.9–101.6%
with an RSD of 1.1–12.8%, an LOQ of 10 μg/kg, and an
LOD of 0.1–5.4 μg/kg. This method is easy, rapid, sensitive,
and practical and meets the requirements of pesticide residue detection
standards.
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