Time filter

Source Type

Niu J.-Z.,Southwest University | Liu G.-Y.,Sichuan Entry Exit Inspection and Quarantine Bureau | Dou W.,Southwest University | Wang J.-J.,Southwest University
Florida Entomologist | Year: 2011

Nine field collected populations of Panonychus citri from Chinese citrus orchards were assayed for susceptibility to pyridaben and the alternative acaricide azocyclotin and activity of glutathione S-transferases (GSTs). The results showed that populations from Pujiang, Wanzhou, and Pengshan exhibited a low level of sensitivity to pyridaben, but demonstrated a high level of sensitivity to azocyclotin. The correlation coefficient between GSTs activities and the LC 50 of pyridaben was r = 0.93 while the correlation coefficient between GSTs activities and the LC 50 of azocyclotin was r = 0.03. The V max value of CDNB (1-chloro-2, 4-dinitrobenzene) in populations from Beibei, Jintang, Pengshan, Wanzhou, and Zhongxian exhibited a: 2.5-, 11.6-, 7.0-, 5.1-, and 6.4-fold increase in resistance, respectively, relative to the pyridaben susceptible population. In addition, azocyclotin was the most sensitive inhibitor of the GSTs compared with the EA (ethacrynic acid) and pyridaben, based on the values for I 50. The current study suggested that GSTs might be involved in resistance of P. citri to pyridaben and but not azocyclotin in the field. Source

Li Y.,University of Sichuan | Hu J.,Sichuan Entry Exit Inspection and Quarantine Bureau | Shi Y.,University of Sichuan | Sun A.,University of Sichuan | Sun C.,University of Sichuan
Food Analytical Methods | Year: 2011

A high-performance liquid chromatography-electrospray ionization-tandem mass spectrometric method for simultaneous determination of seven adulterants including pseudoephedrine, norpseudoephedrine, caffeine, strychnine, fenfluramine, sildenafil, and amfepramone in slimming functional foods was established. For tablet formulation, the target chemicals were extracted with ammoniated methanol, while for liquid samples, plant powder, or capsules formulations, these chemicals were extracted with a mixture solution of ammoniated methanol-diethyl ether (2:1 v/v). After anhydrous sodium sulfate being added, the extracts were centrifuged and then the supernatant was evaporated to dryness under condition of a nitrogen gas flow. The residue was reconstituted with acetonitrile-water (1:9 v/v) to produce a test solution. Chromatographic separation was accomplished using a RP-C18 column with a gradient elution procedure using 0.03% formic acid in acetonitrile and 0.01% formic acid solution. Seven chemicals were separated and detected in 10 min. Clenbuterol was used as an internal standard. The recoveries of seven targeted chemicals in different formulations are from 81.2% to 110.3%. Limits of detection of the method are from 4.2 to 16.7 μg kg -1 with relative standard deviations of 1.1-8.4%. The linearity of the method ranges from 2.0 to 500 ng mL -1 for all chemicals, with linear correlation coefficients varying from 0.9982 to 0.9992. The method has been used for determining the target chemicals in nine slimming functional foods, and satisfactory results are achieved. Among these tested samples, norpseudoephedrine and fenfluramine were not detected for all samples. Some other components, such as pseudoephedrine, amfepramone, strychnine, and sildenafil were detected in one or more samples, while caffeine was detected in almost all of these tested samples. © 2011 Springer Science+Business Media, LLC. Source

Li Y.,University of Sichuan | Zhang H.,U.S. Center for Disease Control and Prevention | Hu J.,Sichuan Entry Exit Inspection and Quarantine Bureau | Xue F.,University of Sichuan | Sun C.,University of Sichuan
Journal of Chromatographic Science | Year: 2012

A gas chromatography-electron impact-tandem mass spectrometric method was established for the simultaneous determination of seven adulterants, including fenfluramine (FEN), norpseudoephedrine (NPE), pseudoephedrine (PSE), ephedrine (EPH), amfepramone (AMF), sibutramine (SIB) and strychnine (STR) in slimming functional foods. The target chemicals were extracted with 2 formic acid solution and then cleaned-up with solid-phase extraction using a strong cation exchange cartridge from tablet, liquid, mixed plant powder and capsule formulations. Chromatographic separation was accomplished on a VF-5MS column within 23 min. Leucomalachite green was employed as an internal standard. The recoveries of seven target chemicals in two formulations ranged from 80.1 to 106. Limits of detection of the method were from 7.5 to 375 g/kg with relative standard deviations of 1.6 to 13.9. The linearity of the method ranged from 90 to 1500 ng/mL for NPE, 150 to 1500 ng/mL for STR, 10 to 500 ng/mL for AMF, 5.0 to 500 ng/mL for PSE and EPH and 3.0 to 500 ng/mL for FEN and SIB. This method was applied to the determination of six brands of slimming functional foods. SIB was detected in five of the samples with the contents in the range of 10.3 - 8.55 × 105 μg/kg. © 2012 The Author [2012]. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissionsoup.com. Source

Gu A.,Sichuan University | Li Z.,Sichuan Entry Exit Inspection and Quarantine Bureau | Liu S.,Sichuan University | Gong T.,Sichuan University | Yu Z.,Sichuan University
Journal of Polymer Research | Year: 2013

Poly(phenylene sulfide ether) (PPSE) with increased molecular weight was synthesized by means of the quantitative conversion of a poly(phenylene sulfoxide ether sulfide ether) (PPSOESE) precursor via a modified reduction method. PPSOESE precursor was prepared in good yield using polycondensation reaction between bis(4-fluorophenyl) sulfoxide (BFPSO) and bis(4-hydroxyphenyl) sulfide (BHPS). The effects of reaction conditions on the synthesis of PPSOESE and its conversion to PPSE were examined and the conditions were optimized. The results showed that the solvent, reaction temperature, and total monomer concentration are important factors affecting the yield and molecular weight of PPSOESE. For the reduction of PPSOESE to PPSE, the solvents and the feeding rate of the reducing reagent are key factors controlling the quantitative conversion of sulfoxide to sulfide. Structural characterization displayed that PPSOESE is amorphous and has the desired linear structure, and the derived PPSE is semicrystalline with low crystallinity. The study indicated that alternative introduction of ether units induces a gauche conformation relative to that of poly(phenylene sulfide) (PPS), resulting in crystallinity depression. PPSE with a number-average molecular weight of 1.7 × 104 g mol-1 was obtained in 92.4 % yield, which was much higher than that previously reported for PPSE. Thermal analyses showed that the glass transition temperature (Tg) and the melting temperature (Tm) of the obtained PPSE are 92 °C and 192 °C, respectively. Thermogravimetric analysis indicated that PPSE has high thermal stability with a degradation onset temperature above 470 °C. © 2013 Springer Science+Business Media Dordrecht. Source

Gu A.,University of Sichuan | Li Z.,Sichuan Entry Exit Inspection and Quarantine Bureau | Yu Z.,University of Sichuan | Xu L.,University of Sichuan
Journal of Applied Polymer Science | Year: 2013

Poly(phenylene sulfide ether) and poly(phenylene sulfoxide ether sulfide ether) (PPSOESE) were successfully prepared and their structures were proved by several analytical techniques in the present work. The molecular weight (MW) of PPSOESE, a soluble polymer in common organic solvent at room temperature, was determined by gel permeation chromatography. Based on the conversion reaction of the two polymers, the MW of PPSE was calculated and correlated with its intrinsic viscosity. As a result, the Mark-Houwink equation for PPSE was concluded. Copyright © 2013 Wiley Periodicals, Inc. Source

Discover hidden collaborations