The Experts below are selected from a list of 252 Experts worldwide ranked by ideXlab platform
Wilber Lwande - One of the best experts on this subject based on the ideXlab platform.
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Cleome hirta essential oil as livestock tick (Rhipicephalus appendiculatus) and maize weevil (Sitophilus zeamais) repellent
Fitoterapia, 1999Co-Authors: M.w. Ndungu, Sumesh C. Chhabra, Wilber LwandeAbstract:The repellency of the essential oil of the shrub Cleome hirta and of three identified constituents (phytol, (+)-cedrol, n-octacosane) was evaluated against the livestock tick, Rhipicephalus appendiculatus and the maize weevil, Sitophillus zeamais. In a tick climbing repellency bioassay, the oil exhibited repellency which, at the highest dose, was comparable to that of the commercial arthropod repellent N,N-Diethyltoluamide (DEET). In a Y-tube olfactometer bioassay, the oil showed higher or comparable repellency against S. zeamais relative to DEET at all the doses tested. The potential of C. hirta in livestock tick and maize weevil control is discussed.
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Gynandropsis gynandra essential oil and its constituents as tick (Rhipicephalus appendiculatus) repellents
Phytochemistry, 1999Co-Authors: Wilber Lwande, M.w. Ndungu, Lambert Moreka, A Hassanali, E Nyandat, Albert Ndakala, H. Amiani, Peter M. Gitu, M. M. Malonza, D. K. PunyuaAbstract:Abstract The repellency of the essential oil of the previously reported anti-tick pasture shrub Gynandropsis gynandra and identified constituents of the oil were evaluated against the livestock tick, Rhipicephalus appendiculatus. In a tick-climbing repellency bioassay, the oil of G. gynandra exhibited a repellency effect which at the highest treatment levels was higher than that of the commercial arthropod repellent N,N-Diethyltoluamide. Twenty eight compounds were identified in the G. gynandra oil by GC, GC-MS and coinjection with authentic samples. Carvacrol was found to occur in largest quantity (29.2%), followed by trans-phytol (24.0%), linalool (13.3%), trans-2-methylcyclopentanol (7.2%) and β-caryophyllene (4.4%). m-Cymene, nonanal, 1-α-terpineol, β-cyclocitral, nerol, trans-geraniol, carvacrol, β-ionone, trans-geranylacetone, and nerolidol were the most repellent components against R. appendiculatus. Methyl isothiocyanate which occurred in the G. gynandra oil at a relative percentage of 2.1 and which was not tested in the bioassay due to its toxicity may also contribute significantly to the repellency of the oil. The repellency of the oil of G. gynandra supported earlier findings by other workers that G. gynandra repelled R. appendiculatus ticks.
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essential oils of lippia species in kenya iv maize weevil sitophilus zeamais repellancy and larvicidal activity
International Journal of Pharmacognosy, 1992Co-Authors: J W Mwangi, Wilber Lwande, Ivan Addaemensah, G Muriuki, Raphael M Munavu, A HassanaliAbstract:AbstractThe repellancy of essential oils of eight Lippia species on maize weevils was compared with NN-Diethyltoluamide (DEET). The larvicidal activity of these essential oils was also examined. As a repellant, the essential oil of L. ukambensis (chemotype camphor) was the most active. Other promising repellants were the essential oils of L. javanica, L. dauensis, L. somalensis and L. grandifolia. The essential oil of L. wilmsii was the most active as a larvicide. Individual hydrocarbon monoterpene constituents were generally more active than the oxygenated constituents of the essential oils.
Sylvain Merel - One of the best experts on this subject based on the ideXlab platform.
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critical assessment of the ubiquitous occurrence and fate of the insect repellent n n diethyl m toluamide in water
Environment International, 2016Co-Authors: Sylvain Merel, Shane A. SnyderAbstract:Abstract The insect repellent Diethyltoluamide (DEET) is among the most frequently detected organic chemical contaminants in water across a wide range of geographies from around the world. These observations are raising critical questions and increasing concerns regarding potential environmental relevance, particularly when the emergence of severe neurological conditions attributed to the Zika virus has increased the use of insect repellents. After dermal application, DEET is washed from the skin when bathing and enters the municipal sewer system before discharge into the environment. Mainly measured by gas chromatography or liquid chromatography coupled to mass spectrometry (GC‐MS or LC-MS), more than 200 peer-reviewed publications have already reported concentrations of DEET ranging ng/L to mg/L in several water matrices from North America, Europe, Asia, Oceania, and more recently Africa and South America. While conventional wastewater treatment technology has limited capacity of removal, advanced technologies are capable of better attenuation and could lower the environmental discharge of organic contaminants, including DEET. For instance, adsorption on activated carbon, desalinating membrane processes (nanofiltration and reverse osmosis), ozonation, and advanced oxidation processes can achieve 50% to essentially 100% DEET attenuation. Despite the abundant literature on the topic, the ubiquity of DEET in the environment still raises questions due to the apparent lack of obvious spatio-temporal trends in concentrations measured in surface water, which does not fit the expected usage pattern of insect repellents. Moreover, two recent studies showed discrepancies between the concentrations obtained by GC‐MS and LC-MS analyses. While the occurrence of DEET in the environment is well established, the concentrations reported should be interpreted cautiously, considering the disparities in methodologies applied and occurrence patterns observed. Therefore, this manuscript provides a critical overview of the origin of DEET in the environment, the relevant analytical methods, the occurrence reported in peer-reviewed literature, and the attenuation efficacy of water treatment processes.
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Potential analytical interferences and seasonal variability in Diethyltoluamide environmental monitoring programs
Chemosphere, 2015Co-Authors: Sylvain Merel, Andrey I. Nikiforov, Shane A. SnyderAbstract:Abstract N,N-diethyl-m-toluamide (DEET), the active component of many insect repellents, is among the most frequently detected compounds in aqueous environments with concentrations reported in the ng L−1 to μg L−1 range. However, DEET is often detected in blanks and reported concentrations differ significantly depending on the analytical technique employed. In addition, relatively sparse data are available regarding the seasonal variability of DEET concentrations in water and there are apparent inconsistencies with expected use patterns. Therefore, the present study investigates potential interferences affecting the detection and quantification of DEET then the geographical and seasonal variations of DEET concentrations. To examine potential analytical interferences, DEET was analyzed in five geographically-diverse wastewater effluents using both gas chromatography and liquid chromatography coupled to mass spectrometric detectors. At times, the concentrations quantified by the employed analytical methods varied significantly. Five compounds with similar molecular weights and structures as DEET were investigated as potential mimics and some were shown to induce an overestimation of DEET. Further experimentation suggested that the solvents used in sample preparation and HPLC analysis are another possible source of interference. Besides potential interferences, the seven-month weekly monitoring of DEET in the primary effluent of a wastewater treatment plant demonstrated a clear seasonal trend with decreasing concentration from summer to winter. These data collectively demonstrate that there are many challenges in the quantification of DEET in complex environmental samples and that co-occurrence of similarly structured substances present in the water sample and/or the solvents used for the analysis could induce analytical bias.
Shane A. Snyder - One of the best experts on this subject based on the ideXlab platform.
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critical assessment of the ubiquitous occurrence and fate of the insect repellent n n diethyl m toluamide in water
Environment International, 2016Co-Authors: Sylvain Merel, Shane A. SnyderAbstract:Abstract The insect repellent Diethyltoluamide (DEET) is among the most frequently detected organic chemical contaminants in water across a wide range of geographies from around the world. These observations are raising critical questions and increasing concerns regarding potential environmental relevance, particularly when the emergence of severe neurological conditions attributed to the Zika virus has increased the use of insect repellents. After dermal application, DEET is washed from the skin when bathing and enters the municipal sewer system before discharge into the environment. Mainly measured by gas chromatography or liquid chromatography coupled to mass spectrometry (GC‐MS or LC-MS), more than 200 peer-reviewed publications have already reported concentrations of DEET ranging ng/L to mg/L in several water matrices from North America, Europe, Asia, Oceania, and more recently Africa and South America. While conventional wastewater treatment technology has limited capacity of removal, advanced technologies are capable of better attenuation and could lower the environmental discharge of organic contaminants, including DEET. For instance, adsorption on activated carbon, desalinating membrane processes (nanofiltration and reverse osmosis), ozonation, and advanced oxidation processes can achieve 50% to essentially 100% DEET attenuation. Despite the abundant literature on the topic, the ubiquity of DEET in the environment still raises questions due to the apparent lack of obvious spatio-temporal trends in concentrations measured in surface water, which does not fit the expected usage pattern of insect repellents. Moreover, two recent studies showed discrepancies between the concentrations obtained by GC‐MS and LC-MS analyses. While the occurrence of DEET in the environment is well established, the concentrations reported should be interpreted cautiously, considering the disparities in methodologies applied and occurrence patterns observed. Therefore, this manuscript provides a critical overview of the origin of DEET in the environment, the relevant analytical methods, the occurrence reported in peer-reviewed literature, and the attenuation efficacy of water treatment processes.
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Potential analytical interferences and seasonal variability in Diethyltoluamide environmental monitoring programs
Chemosphere, 2015Co-Authors: Sylvain Merel, Andrey I. Nikiforov, Shane A. SnyderAbstract:Abstract N,N-diethyl-m-toluamide (DEET), the active component of many insect repellents, is among the most frequently detected compounds in aqueous environments with concentrations reported in the ng L−1 to μg L−1 range. However, DEET is often detected in blanks and reported concentrations differ significantly depending on the analytical technique employed. In addition, relatively sparse data are available regarding the seasonal variability of DEET concentrations in water and there are apparent inconsistencies with expected use patterns. Therefore, the present study investigates potential interferences affecting the detection and quantification of DEET then the geographical and seasonal variations of DEET concentrations. To examine potential analytical interferences, DEET was analyzed in five geographically-diverse wastewater effluents using both gas chromatography and liquid chromatography coupled to mass spectrometric detectors. At times, the concentrations quantified by the employed analytical methods varied significantly. Five compounds with similar molecular weights and structures as DEET were investigated as potential mimics and some were shown to induce an overestimation of DEET. Further experimentation suggested that the solvents used in sample preparation and HPLC analysis are another possible source of interference. Besides potential interferences, the seven-month weekly monitoring of DEET in the primary effluent of a wastewater treatment plant demonstrated a clear seasonal trend with decreasing concentration from summer to winter. These data collectively demonstrate that there are many challenges in the quantification of DEET in complex environmental samples and that co-occurrence of similarly structured substances present in the water sample and/or the solvents used for the analysis could induce analytical bias.
M.w. Ndungu - One of the best experts on this subject based on the ideXlab platform.
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Cleome hirta essential oil as livestock tick (Rhipicephalus appendiculatus) and maize weevil (Sitophilus zeamais) repellent
Fitoterapia, 1999Co-Authors: M.w. Ndungu, Sumesh C. Chhabra, Wilber LwandeAbstract:The repellency of the essential oil of the shrub Cleome hirta and of three identified constituents (phytol, (+)-cedrol, n-octacosane) was evaluated against the livestock tick, Rhipicephalus appendiculatus and the maize weevil, Sitophillus zeamais. In a tick climbing repellency bioassay, the oil exhibited repellency which, at the highest dose, was comparable to that of the commercial arthropod repellent N,N-Diethyltoluamide (DEET). In a Y-tube olfactometer bioassay, the oil showed higher or comparable repellency against S. zeamais relative to DEET at all the doses tested. The potential of C. hirta in livestock tick and maize weevil control is discussed.
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Gynandropsis gynandra essential oil and its constituents as tick (Rhipicephalus appendiculatus) repellents
Phytochemistry, 1999Co-Authors: Wilber Lwande, M.w. Ndungu, Lambert Moreka, A Hassanali, E Nyandat, Albert Ndakala, H. Amiani, Peter M. Gitu, M. M. Malonza, D. K. PunyuaAbstract:Abstract The repellency of the essential oil of the previously reported anti-tick pasture shrub Gynandropsis gynandra and identified constituents of the oil were evaluated against the livestock tick, Rhipicephalus appendiculatus. In a tick-climbing repellency bioassay, the oil of G. gynandra exhibited a repellency effect which at the highest treatment levels was higher than that of the commercial arthropod repellent N,N-Diethyltoluamide. Twenty eight compounds were identified in the G. gynandra oil by GC, GC-MS and coinjection with authentic samples. Carvacrol was found to occur in largest quantity (29.2%), followed by trans-phytol (24.0%), linalool (13.3%), trans-2-methylcyclopentanol (7.2%) and β-caryophyllene (4.4%). m-Cymene, nonanal, 1-α-terpineol, β-cyclocitral, nerol, trans-geraniol, carvacrol, β-ionone, trans-geranylacetone, and nerolidol were the most repellent components against R. appendiculatus. Methyl isothiocyanate which occurred in the G. gynandra oil at a relative percentage of 2.1 and which was not tested in the bioassay due to its toxicity may also contribute significantly to the repellency of the oil. The repellency of the oil of G. gynandra supported earlier findings by other workers that G. gynandra repelled R. appendiculatus ticks.
Joerg Oehlmann - One of the best experts on this subject based on the ideXlab platform.
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Do contaminants originating from state-of-the-art treated wastewater impact the ecological quality of surface waters?
PloS one, 2013Co-Authors: Daniel Stalter, Axel Magdeburg, Kristin Quednow, Alexandra Botzat, Joerg OehlmannAbstract:Since the 1980s, advances in wastewater treatment technology have led to considerably improved surface water quality in the urban areas of many high income countries. However, trace concentrations of organic wastewater-associated contaminants may still pose a key environmental hazard impairing the ecological quality of surface waters. To identify key impact factors, we analyzed the effects of a wide range of anthropogenic and environmental variables on the aquatic macroinvertebrate community. We assessed ecological water quality at 26 sampling sites in four urban German lowland river systems with a 0–100% load of state-of-the-art biological activated sludge treated wastewater. The chemical analysis suite comprised 12 organic contaminants (five phosphor organic flame retardants, two musk fragrances, bisphenol A, nonylphenol, octylphenol, Diethyltoluamide, terbutryn), 16 polycyclic aromatic hydrocarbons, and 12 heavy metals. Non-metric multidimensional scaling identified organic contaminants that are mainly wastewater-associated (i.e., phosphor organic flame retardants, musk fragrances, and Diethyltoluamide) as a major impact variable on macroinvertebrate species composition. The structural degradation of streams was also identified as a significant factor. Multiple linear regression models revealed a significant impact of organic contaminants on invertebrate populations, in particular on Ephemeroptera, Plecoptera, and Trichoptera species. Spearman rank correlation analyses confirmed wastewater-associated organic contaminants as the most significant variable negatively impacting the biodiversity of sensitive macroinvertebrate species. In addition to increased aquatic pollution with organic contaminants, a greater wastewater fraction was accompanied by a slight decrease in oxygen concentration and an increase in salinity. This study highlights the importance of reducing the wastewater-associated impact on surface waters. For aquatic ecosystems in urban areas this would lead to: (i) improvement of the ecological integrity, (ii) reduction of biodiversity loss, and (iii) faster achievement of objectives of legislative requirements, e.g., the European Water Framework Directive.