Photocatalytic degradation with immobilised TiO(2) of three selected neonicotinoid insecticides: imidacloprid, thiamethoxam and clothianidin.
This research focused on photocatalytic degradation of imidacloprid, thiamethoxam and clothianidin employing a tailor-made photoreactor with six polychromatic fluorescent UVA (broad maximum at 355 nm) lamps and immobilised titanium dioxide (TiO(2)) on glass slides. The disappearance was followed by high pressure liquid chromatography (HPLC-DAD) analyses, wherein the efficiency of mineralization was monitored by measurements of total organic carbon (TOC). Within 2h of photocatalysis, all three neonicotinoids were degraded following first order kinetics with rate constants k=0.035 ± 0.001 min(-1) for imidacloprid, k=0.019 ± 0.001 min(-1) for thiamethoxam and k=0.021 ± 0.000 min(-1) for clothianidin. However, the rate of mineralization was low, i.e. 19.1 ± 0.2% for imidacloprid, 14.4 ± 2.9% for thiamethoxam and 14.1 ± 0.4% for clothianidin. This indicates that several transformation products were formed instead. Some of them were observed within HPLC-DAD analyses and structures were proposed according to the liquid chromatography-electro spray ionization tandem mass spectrometry analyses (LC-ESI-MS/MS). The formation of clothianidin, as thiamethoxam transformation product, was reported for the first time.
Laboratory for Environmental Research, University of Nova Gorica, Vipavska 13, P.O. Box 301, 5000 Nova Gorica, Slovenia.
Romina
R
Zabar
Tilen
T
Komel
Jure
J
Fabjan
Mojca Bavcon
MB
Kralj
Polonca
P
Trebše
D002384:Catalysis; D002851:Chromatography, High Pressure Liquid; D002853:Chromatography, Liquid; D006146:Guanidines / Q000737:chemistry* / Q000528:radiation effects; D007093:Imidazoles / Q000737:chemistry* / Q000528:radiation effects; D007306:Insecticides / Q000737:chemistry* / Q000528:radiation effects; D007700:Kinetics; D000073943:Neonicotinoids; D009574:Nitro Compounds / Q000737:chemistry* / Q000528:radiation effects; D010078:Oxazines / Q000737:chemistry* / Q000528:radiation effects; D010782:Photolysis; D053719:Tandem Mass Spectrometry; D000077922:Thiamethoxam; D013844:Thiazoles / Q000737:chemistry* / Q000528:radiation effects; D014025:Titanium
D006146:Guanidines; D007093:Imidazoles; D007306:Insecticides; D000073943:Neonicotinoids; D009574:Nitro Compounds; D010078:Oxazines; D013844:Thiazoles; C009495:titanium dioxide; C480342:clothianidin; C082359:imidacloprid; D000077922:Thiamethoxam; D014025:Titanium