Photo-degradation behavior of seven benzoylurea pesticides with C3N4 nanofilm and its aquatic impacts on Scendesmus obliquus.

Present concerns on the residual benzoylurea pesticides (BUPs) are rapidly climbing as their market shares increase and now seven typical compounds were picked to study their photo-degradation behavior and ecological impacts. Carbon nitride (C3N4) nanofilm at a thickness of 50-80 nm was built on the glass slides and utilized to evaluate the photostability of pesticides under visible light. The results showed that the nano-C3N4 can promote the degradation efficiency of BUPs and it follows the first-order dynamic mechanism. They could be divided into three categories with the substituents and their degradations were discriminated in order of chlorofluoro-, chlorofluoroalkoxy- and chlorofluorophenoxy- substituted ones. Analyzing the intermediates by UHPLC-MS, it can be speculated that the similar pathways came to BUPs such as cleavage of urea-bridge, hydroxylation and dehalogenation. It is attractive that they all passed into a same molecule, 2-fluorobenzamide (m/z, 301.14). Moreover Scendesmus obliquus was applied to indicate the ecological impacts of originals and their photoproducts. Exposed to pesticides, the levels of chlorophyll a demonstrated much more inhibition than chlorophyll b. Lufenuron and chlorfuazuron among seven showed the higher toxicity for algal cells and finally the photodegradation products showed the lowest toxicity. The activities of antioxidant enzymes happened to a significant remedy after photodegradation. It can be concluded that the residual BUPs under visible-light irradiation may degrade through similar pathways and reduce the aquatic toxicity with the presence of C3N4 nanofilm.

PEG-modified magnetic Schiff base network-1 materials for the magnetic solid phase extraction of benzoylurea pesticides from environmental water samples.

It is necessary to establish a rapid, simple and environmentally friendly detection method for benzoylurea pesticides (BUs) in environmental water samples because of their toxicity in environmental circulation. Herein, a novel polyethylene glycol (PEG) modified magnetic covalent organic framework material based on the Schiff base reaction was prepared (PEG/Fe3O4@SNW-1). This material was used as a sorbent for enriching five BUs by magnetic solid phase extraction prior to detection via high-performance liquid chromatography. After the optimization of several parameters (such as the salinity, extraction time, amount of sorbent, desorption time, etc.) that influenced the recovery of the magnetic solid phase extraction process, the limits of detection (S/N = 3) were defined as less than 1.0 µg L-1, and the limits of quantitation (S/N = 10) were calculated as being lower than 3.4 µg L-1. A satisfactory linear range of 5-1000 µg L-1 was achieved. Finally, the proposed method was applied to analyze benzoylurea pesticides in three environmental water samples. These results indicated that the proposed method was feasible and demonstrated the potential application of the PEG/Fe3O4@SNW-1 material for detecting similar pesticide residues in environmental water samples.

Dose-dependent effects of flufenoxuron on thyroid system of mature female lizards (Eremias argus) and their offspring.

More and more studies are focusing on toxic effect of pesticides on lizards. However, the responses of different life-stage lizards to pesticides have not been reported. In this study, according to RNA-seq library data, thyroxine 5'-deiodinase activity showed significant difference between mature and immature lizard liver. In addition, triiodothyronine (T3) level in immature lizard serum was higher than that in mature lizard serum. Thus, we investigated the thyroid disruption of flufenoxuron with different concentrations (0, 5, 20 mg/kg) to both mature lizards and their offspring. No significant differences were observed in immature lizard body weight compared between control and exposure groups while the body weight of mature lizards was significantly decreased after flufenoxuron exposure. Moreover, the levels of thyroid hormones and the expression of thyroid related genes changed with exposure concentration of flufenoxuron and exhibited different regulation mechanism between mature and immature lizards. In immature lizard liver, trα, trß, dio1 and ugt genes controlled the thyroid hormone levels interfered by flufenoxuron. In contrast, the thyroxine (T4) pathway in mature lizard liver was significantly disrupted especially by 20 mg/kg flufenoxuron exposure. This study elucidated the different thyroid disruption effects of flufenoxuron to lizards based on different exposure doses and lizard life stages.

Magnetic Dispersive Solid Phase Microextraction Followed by High Performance Liquid Chromatography for Determination of Benzoylurea Pesticides in Water and Juice samples / 分析化学

A magnetic extraction sorbent based on Fe3 O4@poly ( methacrylic acid-co-ethylene dimethacrylate) ( Fe3 O4@MAED ) was synthesized using methacrylic acid and ethylene dimethacrylate as monomer and cross-linker, respectively. The magnetic sorbent was characterized by FTIR spectroscopy, elemental analysis and transmission electron microscopy. At the same time, the Fe3 O4@MAED was used to extract four benzoylurea pesticides in water and juice samples under magnetic dispersive solid phase microextraction ( MDSPME ) format. To obtain the optimal extraction conditions, several parameters, including the amount of sorbent, desorption solvent, extraction and desorption time, pH value, and ionic strength in sample matrix were investigated. Based on this, a fast, simple and sensitive method for the determination of benzoylurea pesticides in water and juice samples was developed by the combination of MDSPME with HPLC equipped with diode array detector. Under the optimized experimental conditions, the developed method possessed expected linear dynamic ranges, coefficients of correlation ( R2>0. 99 ) and sensitivity. The limits of detection (S/N=3) for target analytes were 0. 10-0. 19 μg/L in water and 0. 12-0. 30 μg/L in juice, respectively. The RSDs for intra-day were less than 7% and inter-day RSDs were less than 11%. The developed method was successfully applied to the determination of benzoylurea pesticides residues in water and juice samples and the recoveries of spiked target compounds were in the range of 69. 4%-118. 0%. The results demonstrated that the Fe3 O4@ MAED could extract benzoylurea pesticides effectively through multi-interactions including hydrophobic, hydrogen-bond and ion-exchange interactions between sorbent and analytes.

Study on the simultaneous determination of seven benzoylurea pesticides in Oolong tea and their leaching characteristics during infusing process by HPLC-MS/MS.

A method for the simultaneous determination of 7 benzoylurea pesticides (chlorfluazuron, diflubenzuron, fluazuron, flufenoxuron, hexaflumuron, teflubenzuron and triflumuron) in the manufactured Oolong tea leaves and its infusion was described. The method has a LOD of 0.03-1.00ng/mL, a recovery of 90.4-103% for made tea and 90.3-102% for tea-infused liquid, respectively. By using the proposed method, the leaching characteristics of above 7 pesticides during infusing process were investigated. The experimental results revealed that: (1) diflubenzuron can be most easily extracted out during infusing process, followed by triflumuron, teflubenzuron, hexaflumuron, chlorfluazuron, flufenoxuron and fluazuron. (2) The leaching of flufenoxuron and chlorfluazuron during infusing process seems to be controlled by only their solubility, whereas, the leaching of other 5 benzoylurea insecticides was primarily controlled by their partitioning coefficient between made tea and hot water. The results of this study are helpful for the accurate evaluation of the safety of Oolong tea.