Separation and Identification of Photolysis Products of Clothianidin by Ultra-Performance Liquid Tandem Mass Spectrometry

Abstract

Photolysis of clothianidin by Xenon lamp was investigated by Ultra-Performance Liquid Chromatography Electrospray Ionization tandem mass spectrometry (UPLC-ESI/MS/ MS). Quantitative study on the photodegradation of clothianidin found that the photodegradation obeyed first order kinetics (C ¼ 9.9917e -0.187 t , R 2 ¼ 0.994). The half-life was about 3.6 hours. Qualitative study on photolysis products of clothianidin were taken by checking all total ion spectra of different sample time. A total of eight products was found in this study. The structure of each product was determined by the total ion spectrometry spectrum and daughter-scan spectrum. The mechanism of photodegradation of this pesticide included radical denitration, nucleophilic substitution, and rearrangement, ring-open, and ring-close. Through the analysis of the change of every product and the mass information, the photolysis pathway was drawn. From this study, products of V, VI, and VII seemed more stable than clothianidin.

Environmental fate of nanopesticides: durability, sorption and photodegradation of nanoformulated clothianidin

“…Consistently with literature, 20 – 22 photodegradation curves of clothianidin followed first-order kinetics (0.97 < R 2 < 0.99), from which DT 50 values were calculated ( Fig. 2 , all values are available in Table S5 † ).…”

“…In the water background, 0.92 < DT 50 < 3.61 h, which corresponds to the range of values previously reported for pure clothianidin. 7 , 20 , 23 As frequently observed, 24 – 27 DT 50 values increased as the concentration of clothianidin increased for all formulations and for the pure AI (about three-fold between the lowest and highest concentrations, p < 0.0001). The effect was not related to changes in pH (as pH increased with concentration in NFC and Com, but it decreased with concentration in NFA).…”

“…S2 † ). The mechanisms of clothianidin photodegradation have been studied 20 and mainly consist in radical denitration. The influence of ammonium, phosphate and iron has not been investigated up to now.…”

Synergistic Lemna Duckweed and Microbial Transformation of Imidacloprid and Thiacloprid Neonicotinoids

“…This selective binding makes neonicotinoids more target-specific than many preceding pesticides . Nevertheless, modification of the neonicotinoid insecticidal pharmacophore through microbial activity ,− (largely documented in soil microbes) or an abiotic process such as photolysis − can alter binding specificity and subsequently impact nontarget organisms. For example, loss of the nitro group from imidacloprid can generate desnitro-imidacloprid, , which contains a moiety with a positive charge distribution that influences receptor binding and makes this metabolite 317 times more toxic than imidacloprid , to vertebrates (based on IC 50 ).…”

Transformation and fate of neonicotinoid insecticides during drinking water treatment

“…48 Neonicotinoids are also degraded and transformed via several non-biological processes, including direct and indirect photodegradation, hydrolysis and chlorination. Neonicotinoids (including clothianidin, imidacloprid and thiamethoxam) readily undergo photodegradation, 17,46,[49][50][51][52][53][54] with estimated half-lives for exposure to direct sunlight between 0.2-1.5 days for thiamethoxam, 0.5-3.31 days for clothianidin and 0.36 -2.22 days for imidacloprid (reaction rates are dependent on surface water temperature). 46 However, photoattenuation at depths greater than 8 cm was negligible, which the authors attribute to their environmental persistence.…”