- CoFe2O4@TiO2 decorated reduced graphene oxide nanocomposite for photocatalytic degradation of chlorpyrifos
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Chlorpyrifos is widely used to control pest insects in residential, agricultural, and commercial applications. Its common use has led to the release of chlorpyrifos into sediments, wastewater and water sources. The presence of chlorpyrifos in wastewaters and water sources may affect ecosystem and human health due to its chronicle toxicity to aquatic organisms. In this study, magnetic recoverable CoFe2O4@TiO2 decorated reduced graphene oxide nanocomposite was prepared and used for investigating the photodegradation of chlorpyrifos. The nanocomposite was characterized by using transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy. In photocatalytic degradation of chlorpyrifos experiments, the effect of operating variables such as initial chlorpyrifos concentration, catalyst dosage and contact time was also investigated. The photocatalytic degradation of chlorpyrifos followed the pseudo-first-order kinetic model. The results indicated that the nanocomposite exhibited a high efficient photocatalytic activity on the photodegradation of chlorpyrifos. The nanocomposite was separated from the solution by a magnet and reused after the photodegradation of chlorpyrifos. The recyclable of the nanocomposite is economically significant in the industry.
- Gupta, Vinod Kumar,Eren, Tanju,Atar, Necip,Yola, Mehmet Lütfi,Parlak, Cemal,Karimi-Maleh, Hassan
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- Photocatalytic degradation and intermediates characteristics of chlopyrifos by nano-TiO2
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The photocatalytic degradation and characteristics of corresponding intermediates of pesticide chlopyrifos have been investigated in aqueous solution with TiO2 as photocatalyst. A series of mixed-solution with different chlopyrifos-TiO2 ratios were prepared and then illuminated by high pressure mercury lamp. After the reaction for 30 and 60 min, the samples were taken for further analysis. The determination of the concentration of chlopyrifos by HPLC shows the degradation rate of chlopyrifos increases with the increase of initial concentration in lower range (5-20 mg/L) but decreases in higher range (20-80 mg/L). The highest degradation rate is 51.3% after 30 min photocatalytic degradation with the initial concentration of 20 mg/L. Then after the degradation for 60 min, the highest degradation rate reaches 89.0%. Three kinds of intermediates 3,5,6-trichloro-2-pyridinyl ester, 3,5,6-trichloro-Pyr and diethyl phosphite were identified after GC/MS analysis. According to toxicity database, we found that the toxicity of intermediate diethyl phosphate is much less than that of chlopyrifos, and the toxicity of former two intermediates is slightly higher than that of chlopyrifos but could be neglected due to their low concentration in reaction system. The nano-TiO2 is proved to be an excellent photocatalyst for degradation of chlopyrifos.
- Liu, Xiang-Ying,Wang, Lifeng,Bai, Lian-Yang,Zhou, Xiao-Mao,Luo, Kun
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p. 469 - 476
(2013/11/06)
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- Oxidation of organophosphorus pesticides for the sensitive detection by a cholinesterase-based biosensor
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A potentiometric flow injection-type biosensor developed in our laboratory was used for the determination of organophosphorus pesticides (OPs). The principle of the biosensor is that the degree of inhibition of a sensor enzyme by an OP is dependent on the concentration of the pesticide. The sensor system consisted of a reactor with acetylcholinesterase (AChE) immobilized on a controlled pore glass and a detector with a tubular H+-selective membrane electrode. In order to examine the possibility of enhancing the sensitivity of the sensor by converting OPs to oxidized forms (stronger inhibitors), a comparison of the degree of enzyme inhibition by OPs at 10-6 M before and after their oxidation was made. All of the ten pesticides tested exhibited greater inhibitory power toward the sensor enzyme following oxidation. All of the oxidized pesticides at 10-6 M inhibited the sensor enzyme to a considerable degree, demonstrating the utility of the developed method for the class-specific determination of OPs. A calibration curve for diazinon, over the concentration range of 10-11-10-4 M, was obtained. The lower detection limit was 2 × 10-10 M. Treatment of the inhibited enzyme with pyridine-2-aldoxime restored the enzyme to near full activity, allowing repeated use of the sensor,
- Lee, Hye-Sung,Ah Kim, Young,Ae Cho, Young,Tae Lee, Yong
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p. 571 - 576
(2007/10/03)
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- Fate of Ethyl-1-14C-labelled Chlorpyrifos in Cotton Leaf Worm
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The absorption , metabolism and degradation of ethyl-1-14C-labelled chlorpyrifos in the adult larvae of cotton leaf worm has been investigated in vivo. The synthesis of ethyl-1-14C-chlorpyrifos and some of its degradation products are described. Following topical application of the radioactive insecticide, about 66 percent of the initially applied dose was metabolized in 24 hr. The identified metabolites were O-ethyl-O-3,5,6-trichloro-2-pyridyl phosphorothioate, O,O-diethyl-O-3,5,6-trichloro-2-pyridyl phosphate and O-ethyl-O-3,5,6-trichloro-2-pyridyl phosphate. Three of the isolated degradation products are still unknown.
- Fakhr, I. M. I.,Hegazi, B.,Khatab, M. S.,Zayed, S. M. A. D.
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p. 145 - 154
(2007/10/03)
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- Development of Enzyme-Linked Immunosorbent Assays for the Insecticide Chlorpyrifos. 1. Monoclonal Antibody Production and Immunoassay Design
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The present work describes the production and characterization of monoclonal antibodies (MAbs) to the insecticide chlorpyrifos and their incorporation into several ELISA configurations. With this aim, a collection of chlorpyrifos haptens was synthesized by introducing appropriate spacers in opposite sites of the analyte molecular structure. From mice immunized with protein conjugates of these haptens, several hybridomas secreting MAbs with the ability to sensitively bind the analyte were obtained. MAbs showing the highest affinity to chlorpyrifos in homologous assays (I50 values in the 20-220 nM range) were selected. Hapten heterology involving modifications of the moiety closer to the attachment site provided the highest improvement in sensitivity. MAbs displayed striking differences in their cross-reactivity pattern with structurally related compounds. One MAb (I50 around 10 nM) was incorporated into other ELISA formats. No remarkable changes of assay characteristics, other than immunoreagent consumption and immunoassay procedure, were found. These ELISAs are potentially very valuable analytical tools for the rapid and sensitive determination of this insecticide.
- Manclus, Juan J.,Primo, Jaime,Montoya, Angel
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p. 4052 - 4062
(2007/10/03)
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- A kinetic analysis of hepatic microsomal activation of parathion and chlorpyrifos in control and phenobarbital-treated rats.
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A kinetic analysis of cytochrome P450-mediated desulfuration (activation) or dearylation (detoxication) showed that rat hepatic microsomes have a greater capacity to detoxify and a lower capacity to activate chlorpyrifos compared to parathion. Kinetic curves for the desulfuration of both parathion and chlorpyrifos were biphasic; Kmapps of 0.23 and 71.3 microM were calculated for parathion, and 1.64 and 50.4 microM for chlorpyrifos. While phenobarbital (PB) exposure seemed to generally lower the Kmapps for desulfuration except for the low Km activity on chlorpyrifos, the results were not statistically significant. While the low Km activity contributed 44 and 60% of the control Vmax for parathion and chlorpyrifos, respectively, it contributed 50 and 17% in PB-treated rats. These studies have indicated the presence of a low Km activity capable of functioning at very low substrate concentrations. A single dearylation Kmapp was calculated, 56.0 and 9.8 microM for parathion and chlorpyrifos, respectively. Phenobarbital exposure seemed to raise the Kmapps of dearylation; however, again, the results were not statistically significant. While numerous biochemical factors contribute to the overall toxicity levels of phosphorothionate insecticides, the in vitro efficiencies of hepatic microsomal desulfuration and dearylation of parathion and chlorpyrifos correspond to the acute toxicity levels.
- Ma,Chambers
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