title: Assessment of silicone as support to investigate the transformation routes of organic chemicals under environmental conditions and UV exposure. Application to selected fungicides.
abstract: The suitability of bulk silicone as support to follow the degradation of chemical compounds under environmental conditions and UV radiation is illustrated selecting three fungicides (fenhexamid, FEN; triadimenol, TRI and difenoconazole, DIF) as model compounds. These precursor species were first absorbed in silicone supports (10 mm length × 2 mm i.d. and 0.5 mm thickness) and then kept outdoors for several days (up to 2 months) or exposed to UV radiation (254 nm), from a low pressure mercury lamp, in the laboratory. Degradation of precursor fungicides and by-products formation was followed by liquid chromatography (LC) quadrupole time-of-flight (QTOF) mass spectrometry (MS), after desorption of silicone supports using 0.5 mL of acetonitrile. Half-lives (t(1/2)) measured under UV exposure varied from 5 to 100 min. As regards environmental conditions, the most stable fungicide was DIF, degraded by just 15 % after 2 months; whereas, t(1/2) values of 30 and 83 h were calculated for FEN during summer and autumn, respectively. Supports contained by-products arising from precursor species through de-chlorination, cleavage, hydroxylation, intra-molecular cyclation and oligomerization reactions. Most of them have been previously identified in soil surface, vegetable leaves and water after application of fungicides in agriculture fields. The low cost of silicone tubes (ca. 0.4 Euros), added to their excellent chemical stability and capability to retain precursor species and their by-products, make them ideal supports to follow the transformation routes of organic compounds under environmental and simulated conditions, even for relatively stable species with t(1/2) in the range of weeks or months.
authors: Departamento de Química Analítica, Nutrición y Bromatología, Instituto de Investigación y Análisis Alimentario (IIAA), Universidad de Santiago de Compostela, Santiago de Compostela, Spain.
authors: T
authors: T
authors: Rodríguez-Cabo
authors: I
authors: I
authors: Rodríguez
authors: M
authors: M
authors: Ramil
authors: R
authors: R
authors: Cela
mesh_terms: D000327:Adsorption; D000577:Amides / Q000737:chemistry; D002853:Chromatography, Liquid; D004148:Dioxolanes / Q000737:chemistry; D004785:Environmental Pollutants / Q000737:chemistry*; D005659:Fungicides, Industrial / Q000737:chemistry*; D013058:Mass Spectrometry; D012828:Silicones / Q000737:chemistry*; D014230:Triazoles / Q000737:chemistry; D014466:Ultraviolet Rays
chemical_list: D000577:Amides; D004148:Dioxolanes; D004785:Environmental Pollutants; D005659:Fungicides, Industrial; D012828:Silicones; D014230:Triazoles; C032910:triadimefon; C115058:difenoconazole; C451426:N-(2,3-dichloro-4-hydroxyphenyl)-1-methylcyclohexanecarboxamide