The Experts below are selected from a list of 1413 Experts worldwide ranked by ideXlab platform
Hongyuan Yan - One of the best experts on this subject based on the ideXlab platform.
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vortex assisted magnetic dispersive solid phase microextraction for rapid screening and recognition of Dicofol residues in tea products
Food Chemistry, 2014Co-Authors: Hongyuan Yan, Ning Sun, Xiaoling Cheng, Xiaoling Wang, Xiaoqiang QiaoAbstract:Abstract A simple and rapid vortex-assisted magnetic dispersive solid-phase microextraction (VAMDSME) method coupled with gas chromatography-electronic capture detection was developed for rapid screening and selective recognition of Dicofol in tea products. The magnetic molecularly imprinted microspheres (mag-MIMs) synthesised by aqueous suspension polymerisation using dichlorodiphenyltrichloroethane (DDT) as a dummy template showed high selectivity and affinity to Dicofol in aqueous solution and were successfully applied as special adsorbents of VAMDSME for rapid isolation of Dicofol from complex tea matrix. Good linearity was obtained in a range of 0.2–160 ng g −1 and the limit of detection based on a signal to noise ratio of 3 was 0.05 ng g −1 . The recoveries at three spiked levels ranged from 83.6% to 94.5% with the related standard deviations (RSD) ⩽ 5.0%. The VAMDSME-GC protocol, which took advantages of the selective adsorption of molecularly imprinted microspheres and rapid magnetic phase separation, as well as the short equilibrium time by vortex-assisted, could avoid the time-consuming procedures related to other traditional extraction methods.
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ionic liquid mediated molecularly imprinted solid phase extraction coupled with gas chromatography electron capture detector for rapid screening of Dicofol in vegetables
Journal of Chromatography A, 2013Co-Authors: Hongyuan Yan, Ning Sun, Yehong Han, Chen Yang, Mingyu WangAbstract:New ionic liquid-mediated molecularly imprinted polymers (IL-MIPs) were prepared by precipitation polymerization using 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM(+)PF6(-)) as the auxiliary solvent, α-chloro-DDT as the dummy template, and they were successfully applied as the sorbents of solid-phase extraction (SPE) for rapid screening of Dicofol from cabbage, tomato, and carrot samples. The IL-MIPs were characterized by FTIR, FE-SEM, static adsorption and chromatographic evaluation, and the results revealed that the IL-MIPs had higher adsorption capacity and selectivity to Dicofol in aqueous solution than that of ionic liquid-mediated non-imprinted polymers (IL-NIPs) and non-imprinted polymers (NIPs). Under the optimized conditions, the IL-MIPs-SPE-GC method offered good linearity (0.4-40.0ngg(-1), r(2)=0.9995) and the average recoveries of Dicofol at three spiked levels were in a range of 84.6-104.1% (n=3) with RSD≤7.6%. The proposed method obviously improved the selectivity and purification effect, and eliminated the effect of template leakage on Dicofol quantitative analysis.
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determination of Dicofol in aquatic products using molecularly imprinted solid phase extraction coupled with gc ecd detection
Talanta, 2011Co-Authors: Hui Wang, Hongyuan Yan, Mande Qiu, Jindong Qiao, Gengliang YangAbstract:The novel molecularly imprinted microsphere (MIM) that could be applied as special sorbent was synthesized by aqueous suspension polymerization using 1,1-bis(4-chlorophenyl)-1,2,2,2-tetrachloroethane (α-chloro-DDT) as the dummy template. The obtained MIM exhibited good recognition and selectivity to Dicofol and it was successfully applied as selective sorbent of solid-phase extraction for the determination of Dicofol from aquatic products. At the optimum conditions of the molecularly imprinted solid-phase extraction (MISPE) coupled with GC-ECD, good linearity for Dicofol was achieved in a range of 0.4-100 ng g(-1) (r(2)=0.9995) and the recoveries at three spiked levels were ranged from 85.8% to 101.2% for aquatic products with the relative standard deviation (RSD) less than 5.6%. The presented MISPE-GC-ECD method exhibited the advantages of simplicity, selectivity and sensitivity, and could be potentially applied to the determination of Dicofol in complicated aquatic products.
Celso Omoto - One of the best experts on this subject based on the ideXlab platform.
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deteccao e monitoramento da resistencia de brevipalpus phoenicis geijskes acari tenuipalpidae ao Dicofol
Anais da Sociedade Entomológica do Brasil, 2000Co-Authors: Celso Omoto, Everaldo Batista Alves, P C RibeiroAbstract:A residual bioassay technique was used to characterize the resistance of Brevipalpus phoenicis (Geijskes) to the acaricide Dicofol. Different concentrations of Dicofol were sprayed on citrus leaf disks with a Potter spray tower. After treatment, each leaf disk was placed on an agar-water solution at the concentration of 2.3% in a petri dish. Adult mites were transferred onto the arena and bioassay dishes were kept at 25±1oC, relative humidity of 70±10% and photoperiod of 14h. The mortality was assessed 24h after mite infestation. The estimated LC50s for susceptible and Dicofol-resistant strains were 7.44 µg of Dicofol / ml of distilled water [ppm (A.I.)] (95% CI 6.74 - 8.23) and 422.45 ppm (A.I.) (95% CI 369.41 - 482.80), respectively. The resistance ratio derived from LC50s was about 57-fold. Based on this difference, discriminating concentrations between 32 and 100 ppm (A.I.) were defined for monitoring Dicofol-resistant B. phoenicis. A survey of different B. phoenicis populations collected from commercial citrus groves in the State of Sao Paulo showed significant differences between populations in relation to their responses to Dicofol.
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Cross-resistance between Dicofol and other acaricides in Brevipalpus phoenicis (Acari: Tenuipalpidae)
Anais da Sociedade Entomológica do Brasil, 2000Co-Authors: Everaldo Batista Alves, Celso Omoto, Cláudio Roberto FrancoAbstract:Cross-resistance relationships between Dicofol and other acaricides recommended in citrus were evaluated in Brevipalpus phoenicis (Geijskes) to find alternative products for managing Dicofol-resistant mites. Susceptible and Dicofol-resistant B. phoenicis strains were tested against fenbutatin oxide, propargite, fenpyroximate and bromopropilate. Dicofol-resistant B. phoenicis showed positive cross-resistance to bromopropilate and negative cross-resistance to fenpyroximate. No cross-resistance was detected between Dicofol and the acaricides fenbutatin oxide and propargite. Therefore, among the acaricides tested only bromopropilate should be avoided for managing Dicofol resistance in B. phoenicis.
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protecao de plantas deteccao e monitoramento da resistencia de brevipalpus phoenicis geijskes acari tenuipalpidae ao Dicofol
2000Co-Authors: Celso Omoto, Everaldo Batista Alves, Paulo E C RibeiroAbstract:A residual bioassay technique was used to characterize the resistance of Brevipalpus phoenicis (Geijskes) to the acaricide Dicofol. Different concentrations of Dicofol were sprayed on citrus leaf disks with a Potter spray tower. After treatment, each leaf disk was placed on an agar-water solution at the concentration of 2.3% in a petri dish. Adult mites were transferred onto the arena and bioassay dishes were kept at 25±1°C, relative humidity of 70±10% and photoperiod of 14h. The mortality was assessed 24h after mite infestation. The estimated LC 50 s for susceptible and Dicofol-resistant strains were 7.44 µg of Dicofol / ml of distilled water (ppm (A.I.)) (95% CI 6.74 - 8.23) and 422.45 ppm (A.I.) (95% CI 369.41 - 482.80), respectively. The resistance ratio derived from LC 50 s was about 57-fold. Based on this difference, discriminating concentrations between 32 and 100 ppm (A.I.) were defined for monitoring Dicofol-resistant B. phoenicis. A survey of different B. phoenicis populations collected from commercial citrus groves in the State of Sao Paulo showed significant differences between populations in relation to their responses to Dicofol.
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management of citrus rust mite acari eriophyidae resistance to Dicofol in florida citrus
Journal of Economic Entomology, 1995Co-Authors: Celso Omoto, T. J. Dennehy, C W Mccoy, S E Crane, J W LongAbstract:Cage and field studies of the dynamics of the citrus rust mite, Phyllocoptruta oleivora (Ashmead), resistance to Dicofol appeared to be unstable; the frequency of resistance declined quickly in the absence of selection pressure, Different regimes for Dicofol (twice per year, once per year, Dicofol after 2 yr of its relaxation, and untreated control) were evaluated in Florida in 2 commercial citrus groves during 1990, 1991, and 1992 seasons, We detected a positive relationship between the number of Dicofol applications made per year and the frequency of resistance to Dicofol. Differences in the frequencies of Dicofol-resistant mites in bioassays reflected differences in the neld performance of Dicofol. Use of Dicofol twice per year was not appropriate because of an increased trend in the frequency of resistance from one year to the next. However, using Dicofol once per year, the frequency of resistance to Dicofol returned to a level equal to or less than the frequency before selection after ≈ 12 mo of Dicofol application, We recommend resistance management program for Dicofol for Florida citrus.
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interface between citrus rust mite acari eriophyidae and Dicofol implications for resistance management
Journal of Economic Entomology, 1995Co-Authors: Celso Omoto, T. J. Dennehy, C W Mccoy, S E Crane, J W LongAbstract:Laboratory and field studies were conducted to characterize the interface between citrus rust mite, Phyllocoptruta oleivora (Ashmead), and the acaricide Dicofol. Direct and residual (continuous and discontinuous residues) contacts of Dicofol on susceptible (S) and Dicofol-resistant (R) strains of citrus rust mite were evaluated. The decay in biological activity of different formulations of Dicofol was also measured with both strains. Differences between S and R strains were less pronounced in direct contact than residual contact with Dicofol. When Dicofol was used at high concentrations in residual bioassays (500-1,280 microgram [AI]/ml of water [ppm]), the expression of resistance was very poor on fresh residues of Dicofol. However, as residues decayed, we observed substantially greater mortality of the S strain than the R strain. Field studies showed that Dicofol on citrus fruits becomes biologically inactive to citrus rust mite relatively fast after its application (concentration of 1,280 ppm [AI]). Both S and R strains survived totally when transferred to a 6-d residue. The formulation of Dicofol had an significant effect on the rate of decay in biological activity. Differences in the rate of decay observed in bioassays were consistent with the field performance of Dicofol in controlling citrus rust mite.
Gengliang Yang - One of the best experts on this subject based on the ideXlab platform.
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determination of Dicofol in aquatic products using molecularly imprinted solid phase extraction coupled with gc ecd detection
Talanta, 2011Co-Authors: Hui Wang, Hongyuan Yan, Mande Qiu, Jindong Qiao, Gengliang YangAbstract:The novel molecularly imprinted microsphere (MIM) that could be applied as special sorbent was synthesized by aqueous suspension polymerization using 1,1-bis(4-chlorophenyl)-1,2,2,2-tetrachloroethane (α-chloro-DDT) as the dummy template. The obtained MIM exhibited good recognition and selectivity to Dicofol and it was successfully applied as selective sorbent of solid-phase extraction for the determination of Dicofol from aquatic products. At the optimum conditions of the molecularly imprinted solid-phase extraction (MISPE) coupled with GC-ECD, good linearity for Dicofol was achieved in a range of 0.4-100 ng g(-1) (r(2)=0.9995) and the recoveries at three spiked levels were ranged from 85.8% to 101.2% for aquatic products with the relative standard deviation (RSD) less than 5.6%. The presented MISPE-GC-ECD method exhibited the advantages of simplicity, selectivity and sensitivity, and could be potentially applied to the determination of Dicofol in complicated aquatic products.
T. J. Dennehy - One of the best experts on this subject based on the ideXlab platform.
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management of citrus rust mite acari eriophyidae resistance to Dicofol in florida citrus
Journal of Economic Entomology, 1995Co-Authors: Celso Omoto, T. J. Dennehy, C W Mccoy, S E Crane, J W LongAbstract:Cage and field studies of the dynamics of the citrus rust mite, Phyllocoptruta oleivora (Ashmead), resistance to Dicofol appeared to be unstable; the frequency of resistance declined quickly in the absence of selection pressure, Different regimes for Dicofol (twice per year, once per year, Dicofol after 2 yr of its relaxation, and untreated control) were evaluated in Florida in 2 commercial citrus groves during 1990, 1991, and 1992 seasons, We detected a positive relationship between the number of Dicofol applications made per year and the frequency of resistance to Dicofol. Differences in the frequencies of Dicofol-resistant mites in bioassays reflected differences in the neld performance of Dicofol. Use of Dicofol twice per year was not appropriate because of an increased trend in the frequency of resistance from one year to the next. However, using Dicofol once per year, the frequency of resistance to Dicofol returned to a level equal to or less than the frequency before selection after ≈ 12 mo of Dicofol application, We recommend resistance management program for Dicofol for Florida citrus.
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interface between citrus rust mite acari eriophyidae and Dicofol implications for resistance management
Journal of Economic Entomology, 1995Co-Authors: Celso Omoto, T. J. Dennehy, C W Mccoy, S E Crane, J W LongAbstract:Laboratory and field studies were conducted to characterize the interface between citrus rust mite, Phyllocoptruta oleivora (Ashmead), and the acaricide Dicofol. Direct and residual (continuous and discontinuous residues) contacts of Dicofol on susceptible (S) and Dicofol-resistant (R) strains of citrus rust mite were evaluated. The decay in biological activity of different formulations of Dicofol was also measured with both strains. Differences between S and R strains were less pronounced in direct contact than residual contact with Dicofol. When Dicofol was used at high concentrations in residual bioassays (500-1,280 microgram [AI]/ml of water [ppm]), the expression of resistance was very poor on fresh residues of Dicofol. However, as residues decayed, we observed substantially greater mortality of the S strain than the R strain. Field studies showed that Dicofol on citrus fruits becomes biologically inactive to citrus rust mite relatively fast after its application (concentration of 1,280 ppm [AI]). Both S and R strains survived totally when transferred to a 6-d residue. The formulation of Dicofol had an significant effect on the rate of decay in biological activity. Differences in the rate of decay observed in bioassays were consistent with the field performance of Dicofol in controlling citrus rust mite.
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detection and characterization of the interpopulation variation of citrus rust mite acari eriophyidae resistance to Dicofol in florida citrus
Journal of Economic Entomology, 1994Co-Authors: Celso Omoto, T. J. Dennehy, C W Mccoy, S E Crane, J W LongAbstract:Methods to rear and bioassay the citrus rust mite, Phyllocoptruta oleivora (Ashmead), were developed to detect and characterize resistance to Dicofol. Sustained rearing of P. oleivora was achieved on ‘Sunburst’ mandarin seedlings [ Citrus reticulate Blanco × (C. paradise Macf. × C. reticulata) ] held in Plexiglas cages in the greenhouse. Residual bioassays with dipped or sprayed citrus seedling leaves were used to evaluate the susceptibility to Dicofol of P. oleivora populations from groves with known history of its use. Mite populations from groves with no history of Dicofol use had significantly higher susceptibility to Dicofol than groves in which Dicofol was used regularly. Methods using dipped or sprayed leaves gave similar results. With the leaf-dip method, the LCM50 of a susceptible field population (2.81 µmg Dicofol/ml distilled water [ppm (AI)]; 95% CL 2.32-3.26) was 8.8 times lower than for a field population selected with Dicofol in the laboratory (24.7 ppm [AI]; 95% CL 20.8-28.2). Based on this difference, we established a diagnostic concentration of 10 ppm (AI) for detecting Dicofol-resistant mites, with a leaf-dip bioassay. Results of a survey of 19 commercial Florida citrus groves, in which we used diagnostic concentration bioassays to determine susceptibility of P. oleivora to Dicofol, revealed significant differences between populations, thus confirming resistance to Dicofol.
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enhanced activation is the mechanism of negative cross resistance to chlorpyrifos in the Dicofol ir strain of tetranychus urticae acari tetranychidae
Journal of Economic Entomology, 1992Co-Authors: Renpei Hatano, Jeffrey G Scott, T. J. DennehyAbstract:The mechanism responsible for negative cross-resistance to chlorpyrifos was examined in isogenic Dicofol susceptible (Orchard-12) and resistant (Dicofol-IR) two-spotted spider mites, Tetranychus urticae Koch. The acetylcholinesterase of both strains was equally sensitive to inhibition by chlorpyrifos oxon. However, the Dicofol-IR strain showed increased oxidative activation of chlorpyrifos to chlorpyrifos oxon relative to the Orchard-12 strain, suggesting this mechanism is responsible for the observed negative cross-resistance.
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Dicofol resistance in tetranychus urticae acari tetranychidae cross resistance and pharmacokinetics
Journal of Economic Entomology, 1991Co-Authors: Linda A Fergussonkolmes, Jeffrey G Scott, T. J. DennehyAbstract:Cross-resistance of Dicofol-resistant Tetranychus urticae Koch to 21 pesticides was evaluated. Initial investigations used field-collected Dicofol-resistant and susceptible colonies. Near-isogenic lines, constructed by a series of backcrosses, were used to confirm or reject determinations of cross-resistance derived from evaluations of field-collected colonies. Dicofol-resistant T. urticae showed strong positive cross-resistance to amitraz, bromopropylate, and chlorobenzilate. Moderate negative cross-resistance to ward chlorpyrifos was observed. These results suggest that amitraz, bromopropylate, and chlorobenzilate should not be used in alternation with Dicofol in a resistance management program designed to exploit the instability of Dicofol resistance. The uptake and distribution of (14C)-Dicofol was investigated in near-isogenic lines of susceptible and resistant mites. No difference in the uptake of radiolabel was observed between strains, suggesting that decreased penetration is not a major mechanism of Dicofol resistance. In vivo metabolism studies revealed greater production of water soluble metabolites and lower levels of internal Dicofol in the resistant strain compared with the susceptible. Therefore, the major mechanism of resistance to Dicofol appears to be increased metabolic detoxification.
Everaldo Batista Alves - One of the best experts on this subject based on the ideXlab platform.
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deteccao e monitoramento da resistencia de brevipalpus phoenicis geijskes acari tenuipalpidae ao Dicofol
Anais da Sociedade Entomológica do Brasil, 2000Co-Authors: Celso Omoto, Everaldo Batista Alves, P C RibeiroAbstract:A residual bioassay technique was used to characterize the resistance of Brevipalpus phoenicis (Geijskes) to the acaricide Dicofol. Different concentrations of Dicofol were sprayed on citrus leaf disks with a Potter spray tower. After treatment, each leaf disk was placed on an agar-water solution at the concentration of 2.3% in a petri dish. Adult mites were transferred onto the arena and bioassay dishes were kept at 25±1oC, relative humidity of 70±10% and photoperiod of 14h. The mortality was assessed 24h after mite infestation. The estimated LC50s for susceptible and Dicofol-resistant strains were 7.44 µg of Dicofol / ml of distilled water [ppm (A.I.)] (95% CI 6.74 - 8.23) and 422.45 ppm (A.I.) (95% CI 369.41 - 482.80), respectively. The resistance ratio derived from LC50s was about 57-fold. Based on this difference, discriminating concentrations between 32 and 100 ppm (A.I.) were defined for monitoring Dicofol-resistant B. phoenicis. A survey of different B. phoenicis populations collected from commercial citrus groves in the State of Sao Paulo showed significant differences between populations in relation to their responses to Dicofol.
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Cross-resistance between Dicofol and other acaricides in Brevipalpus phoenicis (Acari: Tenuipalpidae)
Anais da Sociedade Entomológica do Brasil, 2000Co-Authors: Everaldo Batista Alves, Celso Omoto, Cláudio Roberto FrancoAbstract:Cross-resistance relationships between Dicofol and other acaricides recommended in citrus were evaluated in Brevipalpus phoenicis (Geijskes) to find alternative products for managing Dicofol-resistant mites. Susceptible and Dicofol-resistant B. phoenicis strains were tested against fenbutatin oxide, propargite, fenpyroximate and bromopropilate. Dicofol-resistant B. phoenicis showed positive cross-resistance to bromopropilate and negative cross-resistance to fenpyroximate. No cross-resistance was detected between Dicofol and the acaricides fenbutatin oxide and propargite. Therefore, among the acaricides tested only bromopropilate should be avoided for managing Dicofol resistance in B. phoenicis.
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protecao de plantas resistencia cruzada entre o Dicofol e outros acaricidas em brevipalpus phoenicis geijskes acari tenuipalpidae
2000Co-Authors: Everaldo Batista Alves, Celso Omoto E Claudio, R FrancoAbstract:Cross-resistance relationships between Dicofol and other acaricides recommended in citrus were evaluated in Brevipalpus phoenicis (Geijskes) to find alternative products for managing Dicofol-resistant mites. Susceptible and Dicofol-resistant B. phoenicis strains were tested against fenbutatin oxide, propargite, fenpyroximate and bromopropilate. Dicofol- resistant B. phoenicis showed positive cross-resistance to bromopropilate and negative cross-resistance to fenpyroximate. No cross-resistance was detected between Dicofol and the acaricides fenbutatin oxide and propargite. Therefore, among the acaricides tested only bromopropilate should be avoided for managing Dicofol resistance in B. phoenicis.
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protecao de plantas deteccao e monitoramento da resistencia de brevipalpus phoenicis geijskes acari tenuipalpidae ao Dicofol
2000Co-Authors: Celso Omoto, Everaldo Batista Alves, Paulo E C RibeiroAbstract:A residual bioassay technique was used to characterize the resistance of Brevipalpus phoenicis (Geijskes) to the acaricide Dicofol. Different concentrations of Dicofol were sprayed on citrus leaf disks with a Potter spray tower. After treatment, each leaf disk was placed on an agar-water solution at the concentration of 2.3% in a petri dish. Adult mites were transferred onto the arena and bioassay dishes were kept at 25±1°C, relative humidity of 70±10% and photoperiod of 14h. The mortality was assessed 24h after mite infestation. The estimated LC 50 s for susceptible and Dicofol-resistant strains were 7.44 µg of Dicofol / ml of distilled water (ppm (A.I.)) (95% CI 6.74 - 8.23) and 422.45 ppm (A.I.) (95% CI 369.41 - 482.80), respectively. The resistance ratio derived from LC 50 s was about 57-fold. Based on this difference, discriminating concentrations between 32 and 100 ppm (A.I.) were defined for monitoring Dicofol-resistant B. phoenicis. A survey of different B. phoenicis populations collected from commercial citrus groves in the State of Sao Paulo showed significant differences between populations in relation to their responses to Dicofol.