Residue behaviors and dietary risk assessment of dinotefuran and its metabolites in Oryza sativa by a new HPLC-MS/MS method.

In this study, we developed a new method to detect dinotefuran and its metabolites (UF and DN) in Oryza sativa (Rice) by HPLC-MS/MS in multiple reaction monitoring (MRM) modes. The recovery rates for dinotefuran, UF and DN were 82.3-85.8%, 83.7-89.0%, and 81.6-90.2%, respectively. The dissipation kinetics of dinotefuran in rice followed a combined first+first kinetic model, where the half-lives of dinotefuran and its metabolites were determined to be between 0.5 and 2.3days. The dinotefuran residue in brown rice sampled at day 7, 14, and 21 after the last application was 0.4131mg/kg with a very low risk quotient (RQ) value. We recommend that the safety interval of application for rice is 7days. The method developed in this study is simple and rapid, with high accuracy and precision which meet the requirements for quantitative analysis of dinotefuran in rice.

Dissipation and Residues of Dichlorprop-P and Bentazone in Wheat-Field Ecosystem.

Dichlorprop-P and bentazone have been widely used in the prevention and control of weeds in wheat field ecosystems. There is a concern that pesticide residues and metabolites remain on or in the wheat. Thus, the study of the determination and monitoring of their residues in wheat has important significance. A rapid, simple and reliable QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) method was modified, developed and validated for the determination of dichlorprop-P, bentazone and its metabolites (6-hydroxy-bentazone and 8-hydroxy-bentazone) in wheat (wheat plants, wheat straw and grains of wheat) using high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS). The average recoveries of this method ranged from 72.9% to 108.7%, and the limits of quantification (LOQs) were 2.5-12 µg/kg. The dissipation and final residue of four compounds in three provinces (Shandong, Jiangsu and Heilongjiang) in China were studied. The trial results showed that the half-lives of dichlorprop-P and bentazone were 1.9-2.5 days and 0.5-2.4 days in wheat plants, respectively. The terminal residues in grains of wheat and wheat straw at harvest were all much below the maximum residue limit (MRL) of 0.2 mg/kg for dichlorprop-P and 0.1 mg/kg for bentazone established by the European Union (EU, Regulation No. 396/2005).

Dissipation kinetics and residue of LH-2010A in cucumber and soil under greenhouse condition.

LH-2010A is a newly developed fungicide with novel mode of action in the treatment of cucurbit downy mildew. Dissipation kinetics and residue levels of LH-2010A in cucumber were investigated using a QuEChERS method with GC-ECD. Field trials were constructed at three different sites in China in 2013 and 2014. The average recoveries of LH-2010A in fortified samples were between 94.0 and 106.2% for cucumber and between 84.4% and 98.7% for soil, with relative standard deviations within 3%. The dissipation rate of LH-2010A residue was evaluated assuming a pseudo first-order kinetics. The half-lives of LH-2010A were 2.8-4.2 days and 6.3-9.4 days in cucumber and soil samples, respectively. The terminal residues in cucumber were 0.077-0.207 mg/kg and 0.109-0.307 mg/kg on the first day after spray at the recommended dosage and 1.5 times of the recommended dosage, respectively. Using this rapid and sensitive method, we determined the dissipation kinetics and residue level of HL-2010A in cucumber. The suggested MRL value of HL-2010A in cucumber is 0.5 mg/kg. The research would provide guidance for proper and safe use of this newly developed fungicide in cucumber in greenhouse ecosystems.