Study of the degradation of the herbicide clomazone in distilled and in irrigated rice field waters using HPLC-DAD and GC-MS

Abstract

Este estudo avaliou a degradação do herbicida clomazone em água destilada e de campos de arroz irrigado, através de irradiação UV e sob condições naturais. Após a etapa de pré-concentração por extração em fase sólida (SPE), a concentração remanescente foi determinada por cromatografia líquida de alta eficiência com detecção por arranjo de diodos (HPLC-DAD) e a identificação dos produtos de degradação foi efetuada por cromatografia gasosa com espectrometria de massas (GC-MS). Sob irradiação UV, o clomazone foi degradado mais rapidamente na água destilada que na água de superfície. Na água de irrigação, sob luz solar, o clomazone apresentou tempo de meia-vida médio de 3,2 dias em três safras consecutivas, e após a aplicação a concentração na água permaneceu acima de 0,1 µg L -1 por cerca de 20 dias. Diversos subprodutos, tais como 2-clorobenzaldeído e 2-clorobenzeno metanol, foram identificados por GC-MS, evidenciando que a concentração dos intermediários aumentou no início e então eles também sofreram degradação.This study evaluated the degradation of the herbicide clomazone in distilled water and from irrigated rice fields, through UV irradiation and under natural conditions. After a solid phase extraction (SPE) as preconcentration step, the remained concentration of clomazone was determined by high performance liquid chromatography with diode array detection (HPLC-DAD) and the identification of the degradation products was achieved by gas chromatography-mass spectrometry (GC-MS). Under UV irradiation, the clomazone was degraded faster in distilled water than in surface water. In irrigated rice water, under sunlight irradiation, clomazone presented a half-life time average of 3.2 days in three consecutive harvests, and after application the concentration in water remained higher than 0.1 µg L -1 for 20 days. Several by-products, like 2-chlorobenzaldehyde and 2-chlorobenzene methanol, were identified by GC-MS, which evidenced that the concentration of intermediates at the begining increase and then they also undergo degradation.

Microbial Degradation of Clomazone under Simulated California Rice Field Conditions

“…An additional 50 mL of water was added to the soil; it was again extracted and the extracts combined. As per Zanella et al (14), the filtrate was acidified to pH 3 with concd H 3 PO 4 , and concentrated using solid-phase extraction (SPE) cartridges (3 mL, 300 mg C18 Bakerbond; JT Baker, Paris, KY). Each column was sequentially washed with 1 mL of methanol, 1 mL of water, and 1 mL of pH 3 water (acidified with concd H 3 PO 4 ).…”

Environmental Fate and Toxicology of Clomazone

“…Zanella et al (2008) investigated the photodegradation rate of clomazone in both distilled and agricultural field water irradiated for up to 120 min; after 60 min, a 6.5-fold higher concentration remained in agricultural than in distilled water. However, clomazone's rate of degradation in agricultural field water was affected by pH (pH 3 caused more efficient degradation than pH 6); the difference between the two pH values was attributed to the photoFenton process (Zanella et al 2008).…”

Mitigation of dimethazone residues in soil and runoff water from agricultural field

“…[17,18] Dimethazone is highly soluble in water (1100 mg L −1 ) and has a Koc of 150-562 mL g −1. [19] These properties indicate its potential mobility and aquatic environmental pollution.…”