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At least 199 records · Page 11Linked to original sources
PubMed2006

Sensitive determination of thiamethoxam, imidacloprid and acetamiprid in environmental water samples with solid-phase extraction packed with multiwalled carbon nanotubes prior to high-performance liquid chromatography.

This paper describes a novel method for sensitive determination of thiamethoxam, imidacloprid and acetamiprid based on solid-phase extraction with multiwalled carbon nanotubes as the packed materials. Factors that maybe influence the enrichment efficiency, such as sample flow rate, sample pH, and sample volume, were investigated in detail. Under the optimized conditions, the detection limits of thiamethoxam, imidacloprid and acetamiprid were 6.1, 5.4 and 6.7 ng L(-1), respectively. The experimental results indicated that there was good linearity (R2>0.9993) over the range of 0.08 approximately 100 ng mL(-1) and good reproducibility with the relative standard deviations over the range of 0.7 approximately 1.1% (n=6). The proposed method has been applied to the analysis of real-world water samples, and satisfactory achievements were obtained. The average spiked recoveries were in the range of 87.5 approximately 109.8%. All the results indicated that the proposed method could be used for the simultaneous determination of the three pesticides in environmental water samples at trace levels.

Chromatography, High Pressure Liquid↗
PubMed2001

Determination of imidacloprid, metalaxyl, myclobutanil, propham, and thiabendazole in fruits and vegetables by liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry.

Imidacloprid, metalaxyl, myclobutanil, propham, and thiabendazole have been simultaneously determined in strawberries, oranges, potatoes, pears, and melons by matrix solid-phase dispersion (MSPD) followed by liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS) in positive-ion mode. The samples were homogenized with C8 bonded silica as MSPD sorbent, placed in a glass column, and eluted with dichloromethane. Chromatographic separation of the compounds was achieved on a reversed-phase LC column using a methanol-ammonium formate (50 mmol L(-1)) gradient as a mobile phase. Samples were screened by monitoring the protonated molecular ion at m/z 256 for imidacloprid, 280 for metalaxyl, 289 for myclobutanil, and 202 for thiabendazole, and the main fragment at m/z 138 for propham. Positive samples were confirmed by multiple-ion monitoring. The repeatability (<20%) and recovery (>57%) of the method were good, and limits of detection (<0.05 mg kg(-1)) were adequate.

Antinematodal Agents↗
PubMed2004

Effects of a chronic dietary exposure of the honeybee Apis mellifera (Hymenoptera: Apidae) to imidacloprid.

Previous studies have shown that imidacloprid and insecticidally active imidacloprid plant metabolites are rapidly metabolized by honeybees. Accordingly, no striking differences were expected between the acute and the chronic dietary toxicity of imidacloprid to honeybees. More recently, however, an unexpectedly high chronic dietary toxicity to honeybees was reported for imidacloprid and imidacloprid plant metabolites, and a novel pharmacologic mechanism unrelated to the parent toxophor was postulated. In an extensive literature survey, no further evidence was found for the reported high difference between the acute and the chronic dietary toxicity of imidacloprid and its plant metabolites to honeybees. The majority of data indicated a dietary no observed lethal-effect concentration >0.04 and 0.02 mg/L 50% sucrose solution, respectively, for an acute and a chronic dietary exposure of honeybees to either imidacloprid or its plant metabolites. Findings of chronic feeding studies with those plant metabolites where the toxophor had already been cleaved did not support the hypotheses of a novel pharmacologic mechanism unrelated to the parent toxophor. No increased treatment-related mortality or behavioral abnormalities were recorded in four independent research facilities during a 10-day dietary exposure of honeybees of different ages to sucrose solutions spiked with the respective metabolites at 0.0001, 0.001, and 0.010 mg/L 50% sucrose solution.

Administration, Oral↗
PubMed2005

Microbial hydroxylation of imidacloprid for the synthesis of highly insecticidal olefin imidacloprid.

Microorganisms that bring about the aerobic transformation of imidacloprid (IMI) were isolated and screened, and the microbial regio- and stereoselective hydroxylation of IMI was studied. Some bacteria and fungi transformed IMI to 5-hydroxyl IMI. Bacterium Stenotrophomonas maltophilia CGMCC 1.1788 resting cells transformed IMI into R-5-hydroxyl IMI at the highest conversion rate. The enzyme catalyzed the stereoselective hydroxylation at position C12 of IMI in the imidazolidine ring. Under acidic conditions, 5-hydroxyl IMI was converted into olefin IMI in high molar conversion yield. The olefin IMI exhibited about 19 and 2.2 times more insecticidal efficacy than IMI against horsebean aphid imago and nymph, respectively, and about 1.4 times more active than IMI against brown planthopper imago. The transformation rate of IMI by resting cells of S. maltophilia CGMCC 1.1788 was promoted significantly by some carbohydrates and organic acids. The reaction medium with 5% sucrose resulted in 8.3 times greater biotransformation yield as compared with that without sucrose.

Bacteria↗
PubMed2007

Enhanced hydroxylation of imidacloprid by Stenotrophomonas maltophilia upon addition of sucrose.

Sucrose's ability to promote the hydroxylation of imidacloprid (IMI) by bacterium Stenotrophomonas maltophilia strain CGMCC 1.1788 was examined. Both growing culture and resting cells could transform IMI into 5-hydroxy IMI. Adding 2% sucrose to the growing culture transformation broth and 5% sucrose to the resting cell transformation broth resulted in biotransformation yields, respectively, 2.5 and 9 times greater than without sucrose. In the growing culture transformation, sucrose increased biomass, which led to enhance hydroxylation of IMI. In the resting cell transformation, sucrose was used not as a carbon source but as an energy source for cofactor regeneration for hydroxylation of IMI. The hydroxylation activity of IMI was promoted eightfold by adding reduced nicotinamide adenine dinucleotide (NADH) to the cell-free extract. The hydroxylation of IMI was significantly inhibited by P450 inhibitor piperonyl butoxide. It seems that the hydroxylation of IMI by S. maltophilia CGMCC 1.1788 might proceed through a system by cooperating with P450 enzyme.

Culture Techniques↗
PubMed2003

Repellent efficacy of a combination containing imidacloprid and permethrin against sand flies (Phlebotomus papatasi) in dogs.

Infection in dogs and humans with the protozoan parasite Leishmania are widespread in tropical and subtropical countries around the globe. Sand flies of the order Phlebotomus in the Old World and Lutzomyia in the New World function as the vector of this disease. In dogs, skin lesions are the most prominent signs of canine leishmaniasis, besides other complex underlying manifestations. To prevent dogs from sand fly bites and thus transmission of Leishmania, an imidacloprid 10% w/v / permethrin 50% w/v combination was evaluated for its insecticidal and repellent efficacy. Treated and untreated control dogs were exposed weekly to about 200 female Phlebotomus papatasi for a period of four weeks. Dead and alive sand flies were counted for surviving rate evaluation and feeding rate was determined for repellency evaluation. The repellent efficacy was 94.6% (day 1), 93.3% (day 8), 80.0% (day 15), 72.8% (day 22) and 55.9% (day 29).The insecticidal efficacy was 60.0% (day 1), 46.2% (day 8), 42.6% (day 15), 35.2% (day 22) and 29.3% (day 29). The study demonstrated the high repellent potential of the imidacloprid / permethrin combination, thus protecting dogs from sand fly bites.

Animals↗