Extraction of benzoylurea insecticides from tea leaves based on thermoplastic polyethyleneimine embedded magnetic nanoparticle carbon materials.

A novel mosaic structured core-shell composite, Silica@C/Ni (Sil@C/Ni), has been prepared by embedding Ni nanoparticles on the surface of silica microspheres via coordination and carbonization reduction, and was used as magnetic solid-phase extraction sorbents in combination with high performance liquid chromatography (HPLC) for the extraction and determination of four benzoylurea insecticides (BUs) in tea leaves. Based on the fact that hydrogen bonding and hydrophobic interactions exist between the material and BUs, allowing BUs on the surface of the material can achieve rapid mass transfer and improved sorption performance, satisfactory extraction recoveries have been achieved in practical sample applications. Under the optimized experimental conditions, the linear ranges were 0.5-200 µg L-1 for diflubenzuron and triflumuron, 1.0-200 µg L-1 for teflubenzuron and 0.8-200 µg L-1 for flufenoxuron with the correlation coefficients R2 ≥ 0.9991. The method has limits of detection and limits of quantification of 0.2-0.4 µg L-1 and 0.5-1.0 µg L-1, respectively. The intra-day and inter-day relative standard deviations were less than 5%. The actual sample recoveries were 76.63-95.26%. In addition, Sil@C/Ni was used repeatedly for 15 times and still showed a relatively satisfactory recovery of the four BUs. Therefore, Sil@C/Ni has a high stability and can be used as an ideal magnetic solid phase extraction sorbent for the trace enrichment of BUs in tea-leaf samples.

The impacts of chlorothalonil and diflubenzuron on Apis mellifera L. larvae reared in vitro.

Chlorothalonil is a broad-spectrum fungicide and diflubenzuron is an insect growth regulator used to control many insect larvae feeding on agricultural, forest and ornamental plants. Honey bee larvae may be exposed to both via contaminated pollen, in the form of beebread, added to their diet by their adult nurse sisters. In this study, we determined how single (acute: 72 h mortality) and repeated (chronic: mortality until emergence as adults) exposure to chlorothalonil and diflubenzuron in their diet affected honey bee larvae reared in vitro. The tested doses of chlorothalonil (20, 100, or 200 mg/L) did not impact 72 h larval mortality acutely relative to that of the solvent control. The 72 h mortality of larvae exposed to 1.6 mg/L and higher doses of diflubenzuron acutely in their diet (47.2-63.9% mortality) was significantly higher than that of larvae fed the solvent control, with no predictable dose dependent pattern observed. In the chronic toxicity tests, consuming an artificial diet with 30 or 100 mg/L chlorothalonil and 0.8, 1.3 or 2 mg/L diflubenzuron significantly lowered the survival of honey bee larvae over that of larvae feeding on the solvent control diet. We calculated risk quotients (RQs) for both compounds using the data we generated in our experiments. Collectively, the RQs suggest that neither compound is likely to affect larval mortality directly at field relevant doses given that pollen composes only a fraction of the total larval diet. Nevertheless, our data do not preclude any sublethal effects that chronic exposure to either compound may cause.

Fate of 14C-ethion insecticide in the presence of deltamethrin and dimilin pesticides in cotton seeds and oils, removal of ethion residues in oils, and bioavailability of its bound residues to experimental animals.

Ethyl-1-(14)C-ethion and some of its degradation products have been prepared for comparison purposes. Cotton plants were treated with (14)C-ethion alone and in the presence of deltamethrin and dimilin pesticides under conditions simulating local agricultural practice. (14)C-Residues in seeds were determined at harvest time; about 47.5% of (14)C-activity was associated with oil. After further extraction of seeds with ethanol, the ethanol-soluble (14)C-residues accounted for 10.6% of the total seed residues, whereas the cake contained about 37.3% of the total residues as bound residues in the case of ethion only. The bound residues decreased in the presence of deltamethrin and dimilin pesticides and amounted to 8.1 and 10.4% of the total residues, respectively. About 95% of the (14)C-activity in the crude oil could be eliminated by simulated commercial processes locally used for oil refining. Chromatographic analysis of crude cotton oil revealed the presence of ethion monooxon, O,O-diethyl phosphorothioate, and O,O-diethyl phosphoric acid in addition to one unknown compound in the case of ethion alone or ethion and dimilin. The same degradation products are found in the case of ethion and deltamethrin in addition to ethion dioxon, whereas ethanol extract revealed the presence of ethion dioxon and O,O-diethyl phosphoric acid as free metabolites. Acid hydrolysis of the conjugated metabolites in the ethanol extract yielded O,O-diethyl S-hydroxymethyl phosphorodithioate. The bound residues were quite readily bioavailable to the rats. After feeding rats with the cake containing ethion-bound residues, a substantial amount (60%) of (14)C-residues was eliminated in the urine, whereas the (14)C-residues excreted in expired air and feces were 10 and 9%, respectively. About 11% of the radioactive residues were distributed among various organs.