Microalgal bioassays as a test of pesticide photodegradation efficiency in water.
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Analysis of Variance↗
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Results for “Phenylurea Compounds”
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By-products formation during degradation of isoproturon in aqueous solution. I: Ozonation.
The degradation of the herbicide isoproturon during its ozonation in aqueous solution has been investigated with the aim of identifying intermediate as well as final by-products formed. At ambient temperature, phosphate-buffered (pH = 7) isoproturon aqueous solutions (10, 10(-1) and 10(-3) mg/l) were ozonated in a semi-batch reactor, under a continuous flow of ozonated air whose ozone concentration was 9 and 0.9 mg O3/lair for the highest and the two lower herbicide concentrations respectively. Measured steady-state ozone concentrations during the two sets of experiments (i.e. the highest and the lower isoproturon concentration) were 1.9 and 0.7 mg O3/l. Under all of the above conditions, isoproturon was always completely removed in a period ranging between 5 and 15 min, essentially by reacting with molecular ozone. High-performance liquid chromatography-mass spectrometry (HPLC-MS) analyses indicate that primary degradation by-products are formed either by introducing OH groups in the aromatic ring and/or in the side-chain substituents, or by breaking down the isopropyl alkyl chain. The results also show that these primary intermediates are successively degraded yielding low molecular weight compounds such as aldehydes, simple organic acids and alpha-oxo-acids, which have been identified by gas chromatography-electron capture detection (GC-ECD), ion chromatography (IC) and GC-MS, respectively. On the basis of the analytical results, a pathway for the degradation of isoproturon by ozone has been proposed.
Chromatography, High Pressure Liquid↗
Effect of sludge-amendment or nutrient addition on the biodegradation of the herbicide isoproturon in soil.
Adding sludge to agricultural soil results in added organic matter, nutrients and metallic and/or organic pollutants. These components may modify the behaviour of pesticides in the soil. We monitored possible changes in the degradation of the herbicide isoproturon (production of CO2 and degradation products) in soil amended with sludge, heavy metals or nitrogen and phosphorus. The treated and control soils were incubated under controlled conditions for 60 days. The nitrogen and phosphorus had the greatest effect on isoproturon degradation, independent of the presence of pollutants. Mineralisation of the herbicide to CO2 was slow and seemed to be linked to a fast degradation and to the accumulation of a complex degradation product that was neither catabolized nor adsorbed, 4,4'-diisopropylazobenzene. This degradation pathway also produced smaller amounts of non-extractable residues. Sewage sludge had no significant effect on isoproturon degradation, despite a large increase of organic matter mineralisation (factor 2).
Agriculture↗
Determination photostability of selected agrochemicals in water and soil.
The photolysis of selected pesticides in aqueous solutions has been investigated. The photolysis produced different intermediate substances, which were also found to be soil and microbial degradation products. The phototransformation in the presence of TiO2 and humic substances leads to a disappearance of these compounds. The reaction rate is dependent on the semiconductor oxide and concentration. Photoproducts were isolated and characterized by different spectroscopic methods. Results from this study indicate that degradation products of isoproturon are more toxic on Daphnia magna than on the parent compound.
Animals↗
Modelling and prediction of soil sorption coefficients of non-ionic organic pesticides by molecular descriptors.
Soil sorption coefficients (K(OC)) of 185 non-ionic organic heterogeneous pesticides have been studied searching for quantitative structure-property relationships (QSPRs). The chemical description of pesticide structure has been made in terms of some molecular descriptors: count descriptors, topological indices, information indices, fragment-based descriptors and weighted holistic invariant molecular (WHIM) descriptors; these last are statistical indices describing size, shape, symmetry and atom distribution of molecules in the three-dimensional space. Three new topological indices derived from the electrotopological state indices of Kier and Hall were proposed. Multiple linear regression analysis was performed after previous selection of the descriptors mostly correlated to the response by Genetic Algorithms. The obtained results confirm the capability of the proposed approach to give predictive models for one of the most important partition properties, such as soil sorption coefficient (K(OC)).
Algorithms↗
Fate of seven pesticides in an aerobic aquifer studied in column experiments.
The fate of selected pesticides (bentazone, isoproturon, DNOC, MCPP, dichlorprop and 2,4-D) and a metabolite (2,6-dichlorobenzamide (BAM)) was investigated under aerobic conditions in column experiments using aquifer material and low concentrations of pesticides (approximately 25 microg/l). A solute transport model accounting for kinetic sorption and degradation was used to estimate sorption and degradation parameters. Isoproturon and DNOC were significantly retarded by sorption, whereas the retardation of the phenoxy acids (MCPP, 2,4-D and dichlorprop), BAM and bentazone was very low. After lag periods of 16-33 days for the phenoxy acids and 80 days for DNOC, these pesticides were degraded quickly with 0.-order rate constants of 1.3-2.6 microg/l/day. None of the most probable degradation products were detected.
2,4-Dichlorophenoxyacetic Acid↗
Heterogeneous photocatalysed degradation of a herbicide derivative, isoproturon in aqueous suspension of titanium dioxide.
Heterogeneous photocatalysed degradation of a herbicide derivative, N-(4-isopropylphenyl)-N',N'-dimethylurea (Isoproturon, 1) was investigated in aqueous suspensions of titanium dioxide by monitoring the change in absorption intensity and depletion in Total Organic Carbon content as a function of irradiation time. The degradation kinetics was studied under different conditions such as pH, catalyst concentration, substrate concentration, different types of TiO(2) and in the presence of electron acceptors such as hydrogen peroxide (H(2)O(2)), potassium bromate (KBrO(3)) and potassium persulphate (K(2)S(2)O(8)) besides molecular oxygen. The degradation rates were found to be strongly influenced by all the above parameters. The photocatalyst Degussa P25 was found to be more efficient as compared with other photocatalysts. An attempt was made to identify the degradation product through GC-MS analysis technique.
Catalysis↗
Simultaneous multi-analyte determination of estrone, isoproturon and atrazine in natural waters by the RIver ANAlyser (RIANA), an optical immunosensor.
In most medical and environmental applications of biosensors, only single analytes are determined. However, the monitoring of several analytes is obviously preferable in order to gather more information about the sample under analysis. In line with this, different technologies are being developed to obtain multi-analyte sensors. In this paper, an analytical method for the simultaneous determination of three different contaminants-atrazine, isoproturon, and estrone-in natural waters by using an optical immunosensor prototype, the so-called "RIver ANAlyser" (RIANA), is described. RIANA is based on a rapid solid-phase fluoroimmunoassay that takes place at an optical transducer chip. The transducer surface is chemically modified with three analytes derivatives placed in different discrete locations. The sensor surface can be regenerated thus allowing the performance of several measurements with the same transducer. Each test cycle, including one regeneration step, is accomplished in 15 min. Detection limits achieved were 0.155, 0.046, and 0.084 microg/l, for atrazine, isoproturon, and estrone, respectively. Satisfactory repetition, with relative standard deviations between 1.06 and 6.98%, was obtained. Excluding a minor non-specifical binding of the isoproturon antibodies, no cross-reactivity effects were observed. Matrix effects were significant only in the case of wastewater samples. Biosensor measurements were validated using conventional liquid chromatography-mass spectrometry. The results obtained with both techniques were in good agreement.
Atrazine↗
Inhibitors of acyl-CoA:cholesterol O-acyltransferase (ACAT). Part 1: identification and structure-activity relationships of a novel series of substituted N-alkyl-N-biphenylylmethyl-N'-arylureas.
A series of N-alkyl-N-biphenylylmethyl-N'-arylurea and related derivatives represented by 1 have been prepared and evaluated for their ability to inhibit acyl-CoA:cholesterol O-acyltransferase in vitro and to lower plasma cholesterol levels in cholesterol-fed rats in vivo. Linking of two phenyl groups via oxygen and introduction of fluorine at appropriate positions on the biphenyl moiety improved in vitro and in vivo activity. From this series of analogs, compound 40 (FR179254), which had potent in vitro potency (rabbit intestinal microsomes IC50 = 25 nM), showed excellent plasma cholesterol-lowering activity when administered via the diet (ED50 = 0.045 mg/kg). However, the hypocholesterolemic effect of this compound was moderate when dosed by oral gavage in PEG400 as a vehicle (ED50 = 5.3 mg/kg). Modification of the N'-aryl moiety led to the identification of compound 50 (FR182980) which was efficacious in both dosing models (ED50 = 0.034 mg/kg and 0.11 mg/kg, respectively).
Anilides↗
HPLC-DAD and Q-TOF MS techniques identify cause of Daphnia biomonitor alarms in the River Meuse.
Several water companies in The Netherlands use a combination of specifically targeted compound analysis (HPLC-UV and GC-MS) and effect monitoring (continuous biotests) to monitor source water quality and to screen for unknown compounds. In spring 2004, the Daphnia biomonitor at Keizersveer monitoring station alongside the River Meuse recorded several alarms. In this study, the combination of HPLC-DAD and Q-TOF MS techniques was used to identify the so-far unknown microcontaminant related to this Daphnia alarm as 3-cyclohexyl-1,1-dimethylurea. The maximum concentration of this compound in the River Meuse at the time of the alarm was estimated to be 5 microg/L. The response of the waterfleas to this compound was confirmed with a short-term and a long-term verification test. The origin of the pollutant is still unknown. This paper shows that the combined application of on-line continuous biotests and advanced chemical analysis is an effective tool for the detection and identification of unknown, potentially hazardous compounds for surface water quality monitoring. Biological effect monitoring and specific compound analysis complement each other and together provide the best possible insight in rapid surface water quality changes.
Animals↗
Dead Daphnia flag mystery water contaminants.
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Animals↗
Subcritical water extraction to evaluate desorption behavior of organic pesticides in soil.
We evaluated the feasibility of extracting organic pesticides in soil using a hot-water percolation apparatus at 105 degrees C and 120 kPa pressure. Efficiency of the method was assessed by extracting six selected pesticides (acetochlor, atrazine, diazinon, carbendazim, imidacloprid, and isoproturon) from previously equilibrated soil at 13.6-65.8 mg/kg concentration range. Studies were performed on brown forest soil with clay alluviation (Luvisol). The method developed was compared to the traditional batch equilibrium method in terms of desorbed amount of pesticides from soil and extraction time. Pesticides in the liquid phase from the batch sorption experiment and in the effluent from the hot-water percolation were quantified by high-performance liquid chromatography with UV detection. The results of the percolation experiment are in close correlation with those of the conventional soil testing method. Desorbed quantities by hot-water percolation were 85% acetochlor, 62% atrazine, 65% carbendazim, 44% diazinon, 95% imidacloprid, and 84% isoproturon, whereas using batch equilibrium method 101, 66, 64, 37, 81, and 90% were desorbed, expressed as the percentage of the adsorbed amount of pesticide on soil following equilibration. The average time for hot-water extraction was 3.45 min, in contrast to the 16 h time consumption of the traditional batch method. The effect of temperature on stability of selected compounds was also evaluated using pesticide-spiked sand without soil. Recoveries of analytes ranged between 84.6 and 91.1% with reproducibility of 7.9-10.2%, except for diazinon, for which recovery was 59.4% with 14.4% relative standard deviation since decomposition occurred at elevated temperature. The percolation process has been described by a first-order kinetic equation. The parameters calculated from the equation provide an opportunity to estimate the amount of compound available for desorption, the rate of desorption processes in the studied soil-pesticide-water system, and modeling the leaching process to obtain additional information on the environmental behavior of the examined pesticide.
Atrazine↗
Modeling of single-step and multistep adsorption isotherms of organic pesticides on soil.
The aim of this study was to investigate the sorption behavior and mechanisms of the organic pesticides on soil. To establish the sorption isotherms of six commonly used pesticides (acetochlor, atrazine, diazinon, carbendazim, imidacloprid, and isoproturon), laboratory equilibrium studies were performed at extended concentration ranges on brown forest soil using the batch equilibrium technique. The pesticide concentrations in the equilibrated liquid phase were quantified with high-performance liquid chromatograph by ultraviolet detection. The adsorption processes could be described by a single-step (Langmuir) isotherm for acetochlor and carbendazim, by a two-step curve for diazinon, isoproturon, and atrazine, and by a three-step curve for imidacloprid. A nonlinear mathematical model-derived from the Langmuir equation-has been developed that represents well the detected single-step and multistep shaped adsorption isotherms. The interpreted model was found to fit the experimental data well and allows the description of the adsorption profile with great precision. The altered adsorption activity, which was indicated by the step arising on the plot, may represent the existence/occurrence of a different specific type of adsorption mechanism. This binding force starts to operate simultaneously at a critical concentration of solute in the studied soil-pesticide system. The parameters calculated from the equation provide an opportunity to estimate the extent of absorption constant, adsorption capacity, and concentration limit characteristic to the measured stepwise isotherms.
Adsorption↗
Effect of different soil textures on leaching potential and degradation of pesticides in biobeds.
Biobeds can be used to intercept pesticide-contaminated runoff from the mixing/washdown area, creating optimum conditions for sorption and biodegradation such that the amount of pesticide reaching adjacent water bodies is significantly reduced. The biobed is built on the farm using locally available materials, which include, straw, compost, and topsoil. The topsoil acts as the inoculum for the system and is likely to vary in terms of its physical, chemical, and microbiological characteristics from one farm to another. This study therefore investigated the effects of using different soil types on the degradation and leaching potential from biobeds. Three contrasting topsoils were investigated. Leaching studies were performed using isoproturon, dimethoate, and mecoprop-P, which were applied at simulated disposal rates to 1.5 m deep biobeds. Annual average concentrations were similar for each soil type with leaching losses of even the most mobile (Koc = 12-25) pesticide <1.64% of the applied dose. Greater than 98% of the retained pesticides were degraded in all matrices. Degradation studies investigated the persistence of individual pesticides and pesticide mixtures in the different matrices. DT50 values for isoproturon, chlorothalonil, mecoprop-P, and metsulfuron-methyl applied at 4 times the maximum approved rate were similar across the biomix types and were all less than or equal to reported DT50 values for soil treated at approved rates. When applied as a mixture, DT50 values in each biomix increased, indicating that interactions between pesticides are possible. However, DT90 values of <167 days were obtained in all circumstances, indicating a negligible risk of accumulation. Studies therefore indicate that substrate will have little impact on biobed performance so it should be possible to use local soils in the construction process.
2-Methyl-4-chlorophenoxyacetic Acid↗
Preparation and promotion of fruit growth in kiwifruit of fluorinated N-phenyl-N'-1,2,3-thiadiazol-5-yl ureas.
Seventeen phenyl-fluorinated analogues of thidiazuron [N-phenyl-N'-(1,2,3-thiadiazol-5-yl)urea, TDZ] have been prepared and characterized. The effects of each fluorinated urea on growth and quality of kiwifruits (Actinidia deliciosa) were evaluated by comparison with untreated (control) and TDZ-treated fruits. The results obtained showed a clear dependence of the growth-promoting activity of these fluorinated ureas on the pattern and degree of fluorine substitution in the phenyl ring. The most effective for promoting fruit growth was N-(2,3,5,6-tetrafluorophenyl)-N'-(1',2',3'-thiadiazol-5'-yl)urea at 25 ppm (at harvest, treated fruits were 58% heavier than untreated ones) followed by N-(3,5-difluorophenyl)-N'-(1',2',3'-thiadiazol-5'-yl)urea at 10 ppm (50%). Comparatively, TDZ-treated fruits were 31% (10 ppm) and 38% (25 ppm) heavier than untreated ones. The results also indicate that the effects of the more active phenyl-fluorinated ureas on some standard quality parameters of fruits, for example, percent of fruit dry matter content, soluble solids contents, total titratable acids, shape, and internal structure, are similar to those of TDZ. Quantitative structure-activity relationships have been derived for the fruit growth promoting activity of the phenyl-fluorinated analogues of TDZ.
Actinidia↗
Controlled release of isoproturon, imidacloprid, and cyromazine from alginate-bentonite-activated carbon formulations.
Different alginate-based systems of isoproturon, imidacloprid, and cyromazine have been investigated in order to obtain controlled release (CR) properties. The basic formulation [sodium alginate (1.50%), pesticide (0.30%), and water] was modified using different amounts of bentonite and activated carbon. The higher values of encapsulation efficiency corresponded to those formulations prepared with higher percentages of activated carbon, showing higher encapsulation efficiency values for isoproturon and imidacloprid than for cyromazine, which has a higher water solubility. The kinetic experiments of imidacloprid/isoproturon release in water have shown us that the release rate is higher in imidacloprid systems than in those prepared with isoproturon. Moreover, it can be deduced that the use of bentonite and/or activated carbon sorbents reduces the release rate of the isoproturon and imidacloprid in comparison with the technical product and with alginate formulation without modifying agents. The highest decrease in release rate corresponds to the formulations prepared with the highest percentage of activated carbon. The water uptake, permeability, and time taken for 50% of the active ingredient to be released into water, T50, were calculated to compare the formulations. On the basis of a parameter of an empirical equation used to fit the pesticide release data, the release of isoproturon and imidacloprid from the various formulations into water is controlled by a diffusion mechanism. The sorption capacity of the sorbents and the permeability of the formulations were the most important factors modulating pesticide release. Finally, a linear correlation of the T50 values and the content of activated carbon in formulations were obtained.
Alginates↗
Efficacy of ipronidazole in feed and water against histomoniasis in turkeys 4 to 10 weeks of age.
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Administration, Oral↗
Results of a phase I trial of sorafenib (BAY 43-9006) in combination with oxaliplatin in patients with refractory solid tumors, including colorectal cancer.
BACKGROUND: Sorafenib (BAY 43-9006), a multiple kinase inhibitor, has been shown to inhibit tumor growth and tumor angiogenesis by targeting Raf kinase, vascular endothelial growth factor receptor, and platelet-derived growth factor receptor. In phase I studies, sorafenib demonstrated single-agent activity in patients with advanced solid tumors and was successfully combined with oxaliplatin in preclinical studies. This phase I study investigated the safety, pharmacokinetics, and efficacy of sorafenib in combination with oxaliplatin. PATIENTS AND METHODS: Twenty-seven patients with refractory solid tumors were enrolled in the initial dose-escalation part (cohorts 1, 2A, and 2B) and 10 additional patients with oxaliplatin-refractory colorectal cancer were subsequently enrolled in an extension part (cohort 3). Oxaliplatin 130 mg/m2 was given on day 1 of a 3-week cycle and oral sorafenib was administered continuously from day 4 of cycle 1 at 200 mg twice daily (cohort 1) or 400 mg twice daily (cohorts 2A, 2B, and 3). RESULTS: Adverse events were generally mild to moderate and the maximum tolerated dose was not reached. Common adverse events were diarrhea (52% of patients in the dose-escalation part and 20% in the extension part), sensory neuropathy (44% and 20%), and dermatologic toxicities (41% and 80%). No pharmacokinetic interaction between sorafenib and oxaliplatin was detectable. Two patients with gastric cancer had a partial response. Forty-three percent of patients in cohorts 1 and 2A/B and 78% of patients in cohort 3 exhibited stable disease for >or=10 weeks. CONCLUSION: Continuous oral sorafenib 400 mg twice daily was safely combined with oxaliplatin without detectable drug interactions and showed preliminary antitumor activity in this phase I study. This dose is recommended for phase II studies.
Administration, Oral↗