[Polyamidoamine dendrimer-functionalized silica nanocomposite with polydopamine coating for dispersive micro solid-phase extraction of benzoylurea insecticides in water samples].

Pesticides are used in the agricultural production process to ensure the yield and quality of agricultural products. However, in recent years, environmental pollution issues caused by pesticide residues have sparked widespread concern in society. It is important to develop convenient and efficient approaches to detect and monitor pesticide residues. In this study, targeting benzoylurea insecticides (BUs), polyamidoamine dendrimer-functionalized silica nanocomposite with polydopamine coating (SiO2-PAMAM-PDA) was designed and successfully synthesized. First, monodisperse silica nanoparticles were prepared by the hydrolysis of tetraethyl orthosilicate (TEOS) in mixed solution of ethanol, water and ammonia. The silane coupling agent (3-aminopropyl)triethoxysilane was then employed to introduce amino groups into the silica. Silica with the zeroth generation of polyamidoamine (PAMAM) modification (SiO2-PAMAM-G0) was obtained through Michael addition reaction of methyl acrylate. Ethylenediamine was added to polymerize with methyl acrylate using an amidation reaction to form the first-generation PAMAM (SiO2-PAMAM-G1). Finally, by polymerizing dopamine under alkaline conditions (pH=8.5), the SiO2-PAMAM-G1 was coated with PDA. Thus, the final product named SiO2-PAMAM-PDA was obtained. The composite was characterized using a transmission electron microscope (TEM) and an increase in surface roughness indicated the successful grafting of PDA coating. Dopamine structure contains abundant benzene rings and amino and hydroxyl groups. It could bind with BUs through multiple secondary interactions, such as hydrogen bond and π-π stacking interaction. Therefore, the introduction of PDA could effectively enhance the affinity of the material toward benzoylurea insecticides. The prepared nanocomposites were used as sorbents in a dispersive micro solid-phase extraction approach (D-µ-SPE). The established approach was employed to extract and enrich the BUs in water samples before high-performance liquid chromatography (HPLC) analysis. Diflubenzuron, triflumuron, hexaflumuron, and teflubenzuron were chosen as target analytes. The following was a typical D-µ-SPE procedure. The prepared adsorbents measuring 40 mg were first dispersed in an 8-mL sample solution containing 150 g/L NaCl. The dispersion was assisted by 120-s vortexing to ensure full contact between the SiO2-PAMAM-PDA and the targets. Next, the adsorbents were separated from the liquid phase by 4-min centrifugation (5000 r/min). Thereafter, the adsorbed benzoylureas were eluted using 1 mL acetonitrile as desorption solvent by 120-s vortexing. Separated by centrifugation, the eluate was dried under a mild nitrogen stream. The solid remains were redissolved in 0.1 mL of acetonitrile, filtered by filter membrane (0.22 µm), and then analyzed by HPLC. The experimental conditions in the D-µ-SPE process could have a great impact on the extraction efficiency. Experimental conditions were optimized using a single factor optimization approach to further enhance the extraction recoveries. The optimized conditions included adsorbent amount, extraction time, desorption solvent type, desorption solvent volume, desorption time, and NaCl addition amount. Under the optimal conditions, a linearity range of 10-500 µg/L and limits of detection (LODs, S/N=3) of 1.1-2.1 µg/L were obtained. The extraction recoveries and relative standard deviations (RSDs) of the four BUs were 82.8%-94.1% and 2.1%-8.0%, respectively. The established approach was compared with reported approaches targeting benzoylurea insecticides. It was discovered that this approach consumed less sample, material, organic solvent, and pretreatment time. It provided a more rapid and green choice for the determination of benzoylurea pesticides. To determine the applicability, the proposed approach was applied to analyze the four benzoylurea insecticides in three river water samples. The real water samples were pretreated using the developed approach ahead of instrumental analysis, and no benzoylurea pesticides residue was detected. Next, standard addition experiments were performed under three spiking levels, including 15, 50, and 200 µg/L. The established approach had good accuracy and feasibility with satisfactory recoveries (69.5%-99.4%) and RSDs (0.2%-9.5%).

Extraction of benzoylurea insecticides from tea leaves based on thermoplastic polyethyleneimine embedded magnetic nanoparticle carbon materials.

A novel mosaic structured core-shell composite, Silica@C/Ni (Sil@C/Ni), has been prepared by embedding Ni nanoparticles on the surface of silica microspheres via coordination and carbonization reduction, and was used as magnetic solid-phase extraction sorbents in combination with high performance liquid chromatography (HPLC) for the extraction and determination of four benzoylurea insecticides (BUs) in tea leaves. Based on the fact that hydrogen bonding and hydrophobic interactions exist between the material and BUs, allowing BUs on the surface of the material can achieve rapid mass transfer and improved sorption performance, satisfactory extraction recoveries have been achieved in practical sample applications. Under the optimized experimental conditions, the linear ranges were 0.5-200 µg L-1 for diflubenzuron and triflumuron, 1.0-200 µg L-1 for teflubenzuron and 0.8-200 µg L-1 for flufenoxuron with the correlation coefficients R2 ≥ 0.9991. The method has limits of detection and limits of quantification of 0.2-0.4 µg L-1 and 0.5-1.0 µg L-1, respectively. The intra-day and inter-day relative standard deviations were less than 5%. The actual sample recoveries were 76.63-95.26%. In addition, Sil@C/Ni was used repeatedly for 15 times and still showed a relatively satisfactory recovery of the four BUs. Therefore, Sil@C/Ni has a high stability and can be used as an ideal magnetic solid phase extraction sorbent for the trace enrichment of BUs in tea-leaf samples.

Dissipation rates and residue levels of diflubenzuron and difenoconazole on peaches and dietary risk assessment.

The dissipation kinetics, residue levels, and potential risks of diflubenzuron and difenoconazole on peaches were investigated under open field conditions. Two years of field trials were carried out in Shanghai, China, and the half-lives of diflubenzuron and difenoconazole on peaches ranged from 4.4 to 25d. Their terminal residue concentrations on peaches were 0.022-5.7 mg/kg after three of the tested sampling intervals. Based on the maximum residue levels (MRLs) of difenoconazole on peaches, a preharvest interval (PHI) of 14 d was proposed. A PHI of 10 d was proposed for diflubenzuron after a dietary safety assessment. During the safety assessment, the hazard quotient (HQ) and risk quotient (RQ) on peaches were determined. The results showed that the HQs (3.6-8.3%) and RQs(51-55%) of diflubenzuron were acceptable, proving that diflubenzuron poses no potential health risks. For difenoconazole, the HQs (0.027-0.071%) were satisfactory, but the RQs (115-116%) exceeded 100%, which indicated potential risk.

The impacts of chlorothalonil and diflubenzuron on Apis mellifera L. larvae reared in vitro.

Chlorothalonil is a broad-spectrum fungicide and diflubenzuron is an insect growth regulator used to control many insect larvae feeding on agricultural, forest and ornamental plants. Honey bee larvae may be exposed to both via contaminated pollen, in the form of beebread, added to their diet by their adult nurse sisters. In this study, we determined how single (acute: 72 h mortality) and repeated (chronic: mortality until emergence as adults) exposure to chlorothalonil and diflubenzuron in their diet affected honey bee larvae reared in vitro. The tested doses of chlorothalonil (20, 100, or 200 mg/L) did not impact 72 h larval mortality acutely relative to that of the solvent control. The 72 h mortality of larvae exposed to 1.6 mg/L and higher doses of diflubenzuron acutely in their diet (47.2-63.9% mortality) was significantly higher than that of larvae fed the solvent control, with no predictable dose dependent pattern observed. In the chronic toxicity tests, consuming an artificial diet with 30 or 100 mg/L chlorothalonil and 0.8, 1.3 or 2 mg/L diflubenzuron significantly lowered the survival of honey bee larvae over that of larvae feeding on the solvent control diet. We calculated risk quotients (RQs) for both compounds using the data we generated in our experiments. Collectively, the RQs suggest that neither compound is likely to affect larval mortality directly at field relevant doses given that pollen composes only a fraction of the total larval diet. Nevertheless, our data do not preclude any sublethal effects that chronic exposure to either compound may cause.

Occurrence and Distribution of Deltamethrin and Diflubenzuron in Surface Sediments from the Reloncaví Fjord and the Chiloé Inner-Sea (~ 39.5ºS -43ºS), Chilean Patagonia.

Surface sediments from Reloncaví Fjord and the Chiloé inner sea in Chilean Patagonia were extracted and analyzed to estimate deltamethrin and diflubenzuron levels. These antiparasitary pesticides have been used for decades in the salmon industry. Relationships were determined between pesticide concentrations and organic carbon percent in sediments. Deltamethrin (0.39-1.05 µg g-1 dw) was found at all sampling sites but diflubenzuron (0.06-0.09 µg g-1 dw) at only five. Diflubenzuron levels were similar for sediments from other fjord areas. However, deltamethrin concentration was 2-3 fold higher than other studies on this area. The organic carbon percent was correlated positively and significantly with diflubenzuron, but not with deltamethrin. Our results suggest that the high deltamethrin concentrations in sediments are due to the increased use of pyrethroids around salmon farming areas. But, the diflubenzuron levels can be explained by degradation processes.

Evaluation of the safe use and dietary risk of beta-cypermethrin, pyriproxyfen, avermectin, diflubenzuron and chlorothalonil in button mushroom.

In this study, the residues of beta-cypermethrin, pyriproxyfen, avermectin, diflubenzuron and chlorothalonil in button mushrooms were investigated. The dietary risks of ingesting button mushrooms that have had these pesticides applied by two different methods under normal plant conditions were evaluated. The dissipation of these pesticides into the soil was also studied. According to the maximum residue limits (MRLs) and acceptable daily intakes (ADIs), the final residues of beta-cypermethrin, pyriproxyfen, avermectin, diflubenzuron, and chlorothalonil were safe for human consumption after these pesticides were applied by spraying 2 times at the dosages of 900, 750, 540, 562.5, and 540 g a.i.ha-1. The dissipation experiment results demonstrated that these pesticides dissipated rapidly after spraying, and there were no residues that could be detected at harvest time when the pesticides were mixed with substrates. According to this work, the application methods of spraying and incorporation with these pesticides at 1 and 1.5 times of the recommended dosage are safe and proper in cultivating button mushrooms.

Ultrasound-assisted, hybrid ionic liquid, dispersive liquid-liquid microextraction for the determination of insecticides in fruit juices based on partition coefficients.

An ultrasound-assisted, hybrid ionic liquid, dispersive liquid-liquid microextraction method coupled to high-performance liquid chromatography with a variable-wavelength detector was developed to detect ten insecticides, including diflubenzuron, triflumuron, hexaflumuron, flufenoxuron, lufenuron, diafenthiuron, transfluthrin, fenpropathrin, γ-cyhalothrin and deltamethrin, in fruit juices. In this method, an appropriate extraction solvent was chosen based on the partition coefficient of the target compounds. A mixture of 1-octyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide was used as the extractant. The extraction efficiency was screened using Plackett-Burman design and optimized using central composite design. Under the optimal conditions, good linearity was obtained for all the analytes in the pure water model and the fruit juice samples. In pure water, the recoveries of the ten insecticides ranged from 85.7 to 108.9%, with relative standard deviations for one day ranging from 1.24 to 2.64%. The limits of detection were in the range of 0.19-0.69 µg/L, and the enrichment factors were in the range of 123-160. The logarithm of the n-octanol/water partition coefficient in this experiment is a useful reference to select a suitable extraction solvent, and the proposed technique was applied for the analysis of ten insecticides in fruit juice with satisfactory results.

Exploration of the phycoremediation potential of Laminaria digitata towards diflubenzuron, lindane, copper and cadmium in a multitrophic pilot-scale experiment.

The presence of contaminants in aquatic ecosystems can cause serious problems to the environment and marine organisms. This study aims to evaluate the phycoremediation capacity of macroalgae Laminaria digitata for pesticides (diflubenzuron and lindane) and toxic elements (cadmium and copper) in seawater in the presence or absence of mussels. The photosynthetic activity was monitored in the macroalgae to assess its "physiological status". The results showed that the presence of algae decreased diflubenzuron concentration in mussels by 70% after 120 h of exposure. Additionally, this macroalgae was efficient to reduce lindane, Cu and Cd in seawater; even though it not was able to reduce these contaminants in mussels. The studied pollutants did not affect the physiological status of macroalgae. This study reveals that the application of phycoremediation with macroalgae can be an useful and effective mitigation strategy to remove/decrease contaminant levels from the aquatic environment.

Occurrence of antiparasitic pesticides in sediments near salmon farms in the northern Chilean Patagonia.

Growth of the aquaculture industry has triggered the need for research into the potential environmental impact of chemicals used by salmon farms to control diseases. In this study, the antiparasitic pesticides emamectin benzoate (EB), diflubenzuron (DI), teflubenzuron (TE), and cypermethrin (CP) were measured in sediments near salmon cages in southern Chile. Concentrations for EB were between 2.2 and 14.6ngg-1, while the benzoylphenyl ureas DI and TE were detected in the ranges of 0.1 to 1.2ngg-1 and 0.8 to 123.3ngg-1, respectively. These results were similar to data reported for the Northern Hemisphere. On the other hand, the pyrethroid CP was detected in higher concentrations, ranging from 18.0 to 1323.7ngg-1. According to reported toxicity data, this range represents a potential risk for benthic invertebrates. This report is the first baseline attempt at assessing antiparasitic pesticide levels in the Chilean Patagonia.

Persistence and Stability of Teflubenzuron and Diflubenzuron When Associated to Organic Particles in Marine Sediment.

The persistence and stability of the oral administered anti salmon-lice drugs teflubenzuron and diflubenzuron were tested when associated to organic material as faecal particles from Atlantic salmon and medicated food pellets. This laboratory study was performed in seawater under aerobic conditions, at 7°C in the dark and showed that both compounds were remarkably persistent and stable since no significant reduction in the concentrations of flubenzurons in sediment were seen after 24 weeks. Therefore neither chemical or microbial degradation nor outwashing seems to be important pathways for these drugs to disappear from sediment under fish farms. Thus, it is more likely that the decrease of flubenzurons from marine sediments described in field investigations is caused by either bioturbation, resuspension of organic particles or a combination of these.

Determination of diflubenzuron and chlorbenzuron in fruits by combining acetonitrile-based extraction with dispersive liquid-liquid microextraction followed by high-performance liquid chromatography.

In this study, a simple and low-organic-solvent-consuming method combining an acetonitrile-partitioning extraction procedure followed by "quick, easy, cheap, effective, rugged and safe" cleanup with ionic-liquid-based dispersive liquid-liquid microextraction and high-performance liquid chromatography with diode array detection was developed for the determination of diflubenzuron and chlorbenzuron in grapes and pears. Ionic-liquid-based dispersive liquid-liquid microextraction was performed using the ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate as the extractive solvent and acetonitrile extract as the dispersive solvent. The main factors influencing the efficiency of the dispersive liquid-liquid microextraction were evaluated, including the extractive solvent type and volume and the dispersive solvent volume. The validation parameters indicated the suitability of the method for routine analyses of benzoylurea insecticides in a large number of samples. The relative recoveries at three spiked levels ranged between 98.6 and 109.3% with relative standard deviations of less than 5.2%. The limit of detection was 0.005 mg/kg for the two insecticides. The proposed method was successfully used for the rapid determination of diflubenzuron and chlorbenzuron residues in real fruit samples.

Fate of 14C-ethion insecticide in the presence of deltamethrin and dimilin pesticides in cotton seeds and oils, removal of ethion residues in oils, and bioavailability of its bound residues to experimental animals.

Ethyl-1-(14)C-ethion and some of its degradation products have been prepared for comparison purposes. Cotton plants were treated with (14)C-ethion alone and in the presence of deltamethrin and dimilin pesticides under conditions simulating local agricultural practice. (14)C-Residues in seeds were determined at harvest time; about 47.5% of (14)C-activity was associated with oil. After further extraction of seeds with ethanol, the ethanol-soluble (14)C-residues accounted for 10.6% of the total seed residues, whereas the cake contained about 37.3% of the total residues as bound residues in the case of ethion only. The bound residues decreased in the presence of deltamethrin and dimilin pesticides and amounted to 8.1 and 10.4% of the total residues, respectively. About 95% of the (14)C-activity in the crude oil could be eliminated by simulated commercial processes locally used for oil refining. Chromatographic analysis of crude cotton oil revealed the presence of ethion monooxon, O,O-diethyl phosphorothioate, and O,O-diethyl phosphoric acid in addition to one unknown compound in the case of ethion alone or ethion and dimilin. The same degradation products are found in the case of ethion and deltamethrin in addition to ethion dioxon, whereas ethanol extract revealed the presence of ethion dioxon and O,O-diethyl phosphoric acid as free metabolites. Acid hydrolysis of the conjugated metabolites in the ethanol extract yielded O,O-diethyl S-hydroxymethyl phosphorodithioate. The bound residues were quite readily bioavailable to the rats. After feeding rats with the cake containing ethion-bound residues, a substantial amount (60%) of (14)C-residues was eliminated in the urine, whereas the (14)C-residues excreted in expired air and feces were 10 and 9%, respectively. About 11% of the radioactive residues were distributed among various organs.

Comparison of two ionic liquid dispersive liquid-liquid microextraction approaches for the determination of benzoylurea insecticides in wastewater using liquid chromatography-quadrupole-linear ion trap-mass spectrometry: evaluation of green parameters.

Two dispersive liquid-liquid microextraction (DLLME) approaches including temperature-controlled ionic liquid dispersive liquid-liquid microextraction (TCIL-DLLME) and ultrasound-assisted ionic liquid dispersive liquid-liquid microextraction (US-IL-DLLME) were compared for the extraction of six benzoylurea insecticides (diflubenzuron, triflumuron, hexaflumuron, teflubenzuron, lufenuron and flufenoxuron) from wastewater samples prior to their determination by high-performance liquid chromatography with a hybrid triple quadrupole-linear ion trap-mass spectrometer (LC-QqLIT-MS/MS). Influential parameters affecting extraction efficiency were systematically studied and optimized and the most significant green parameters were quantified and compared. The best results were obtained using the US-IL-DLLME procedure, which employed the IL 1-octyl-3-methylimidazolium hexafluorophosphate ([C8MIM][PF6]) and methanol (MeOH) as extraction and disperser solvent, respectively. US-IL-DLLME procedure was fast, easy, low environmental toxicity and, it was also able to successfully extract all selected benzoylureas. This method was extensively validated with satisfactory results: limits of detection and quantification were in the range 0.5-1.0 ng L(-1) and 1.5-3.5 ng L(-1), respectively, whereas recovery rates ranged from 89 to 103% and the relative standard deviations were lower than 13.4%. The applicability of the method was assessed with the analysis of effluent wastewater samples from a wastewater treatment plant located in an agricultural zone of Almería (Spain) and the results indicated the presence of teflubenzuron at mean concentration levels of 11.3 ng L(-1). US-IL-DLLME sample treatment in combination with LC-QqLIT-MS/MS has demonstrated to be a sensitive, selective and efficient method to determine benzoylurea insecticides in wastewaters at ultra-trace levels.

Do antiparasitic medicines used in aquaculture pose a risk to the Norwegian aquatic environment?

Aquaculture production is an important industry in many countries and there has been a growth in the use of medicines to ensure the health and cost effectiveness of the industry. This study focused on the inputs of sea lice medication to the marine environment. Diflubenzuron, teflubenzuron, emamectin benzoate, cypermethrin, and deltamethrin were measured in water, sediment, and biota samples in the vicinity of five aquaculture locations along the Norwegian coast. Deltamethrin and cypermethrin were not detected above the limits of detection in any samples. Diflubenzuron, teflubenzuron, and emamectin benzoate were detected, and the data was compared the UK Environmental Quality Standards. The concentrations of emamectin benzoate detected in sediments exceed the environmental quality standard (EQS) on 5 occasions in this study. The EQS for teflubenzuron in sediment was exceeded in 67% of the samples and exceeded for diflubenzuron in 40% of the water samples collected. A crude assessment of the concentrations detected in the shrimp collected from one location and the levels at which chronic effects are seen in shrimp would suggest that there is a potential risk to shrimp. It would also be reasonable to extrapolate this to any species that undergoes moulting during its life cycle.

Residue behaviour of six pesticides in button crimini during home canning.

The effect of home canning (including washing, boiling, cooling, adding solution and sterilisation) on residue levels of imidacloprid, diflubenzuron, abamectin, pyriproxyfen and ß-cypermethrin and chlorothalonilin on button crimini was assessed. Residues of imidacloprid, diflubenzuron, abamectin and pyriproxyfen were measured by UPLC-MS/MS; the residues of ß-cypermethrin and chlorothalonil were measured by GC. Results showed that washing resulted in a 3.8% reduction of the initial residue level of imidacloprid (p ≤ 0.05). From washing to sterilisation the processing effect was significant compared with raw crimini (p ≤ 0.05), but processing through cooling and adding solution had no effect. For diflubenzuron, from raw crimini to sterilisation the processing effect was significant by comparison with the initial level (p ≤ 0.05); the processing effect was not obvious between two sequential steps, and the sequential steps have list: washing and boiling, boiling and cooling, boiling and adding of solution, cooling and adding solution. The changes in abamectin levels were also significant from raw crimini to sterilisation compared with raw crimini (p ≤ 0.05), but the changes were not obvious from boiling to adding solution and amongst them. For pyriproxyfen, washing resulted in a 39% reduction, but changes were not obvious from washing to sterilisation, p ≤ 0.05 between two consecutive steps. The whole procedure could significantly decrease residues of ß-cypermethrin (p ≤ 0.05); washing could significantly reduce residues of ß-cypermethrin; the effects of last procedures were complicated, and p ≤ 0.05 between two consecutive steps. Washing resulted in an 80% reduction of chlorothalonil; after washing there were no detectable residues. After the whole process, the processing factors for imidacloprid, diflubenzuron, abamectin, pyriproxyfen, ß-cypermethrin and chlorothalonil were 0.40, 0.22, 0.04, 0.85, 0.28 and 0, respectively.

Determination of phenylurea pesticides by direct laser photo-induced fluorescence.

A direct Laser Photo-Induced Fluorescence (DL-PIF) method is developed for the determination of two phenylurea pesticides, namely fenuron and diflubenzuron. The DL-PIF method uses a tunable Nd:YAG-OPO Laser to obtain the photoproduct(s) and to simultaneously analyse their fluorescence in a short acquisition time on an intensified CCD camera. Compared to classical PIF methods, the use of a tunable laser improves the selectivity (by choosing the suitable excitation wavelength), increases the sensitivity (due to the high energy of the beam) and also reduces the time of analysis. The analytical performances of this method for the determination of both pesticides are satisfactory in comparison to other classical PIF methods published for the determination of phenylurea pesticides. The calibration curves were linear over one order of magnitude and the limits of detection were in the ng mL(-1) range. Satisfactory recoveries were obtained in the analysis of both pesticides in river and sea water spiked samples.

Vertical distribution in soil column and dissipation in soil of benzoylurea insecticides diflubenzuron, flufenoxuron and novaluron and effect on the bacterial community.

Benzoylurea insecticides are used for prevention and eradication of household or field pests. However, few studies have investigated their distribution and dissipation in soils and the effects on the soil microbial community. We examined the dissipation and vertical distribution of diflubenzuron, flufenoxuron and novaluron and their effects on bacterial diversity in two soils in Taiwan. The dissipation of the three benzoylureas was concentration dependent. The half-life of 1, 10 and 50 mg kg(-1) concentration was from 3.0 to 45.9, 52.1 to 433.2 and 27.7 to 533.2 d, respectively. The proportion of residual benzoylureas in sterilized soils remained up to 83% at the end of the incubation, which implied that the dissipation was mainly by microorganisms. All three benzoylureas were not detected below 10 cm in soil column experiments. Comparison of initial pesticides concentrations (50 mg kg(-1)), diflubenzuron was detected at <1%. However, flufenoxuron and novaluron remained at >30% and 50% in Pu and Wl soil, respectively after leaching for 70 d. Furthermore, the presence of flufenoxuron and novaluron at 5- to 10-cm depth led to greater change in bacterial community diversity in Pu than Wl soil.

[Determination of diflubenzuron and triflumuron residues in greasy wool by accelerated solvent extraction technique and high performance liquid chromatography].

A method for the determination of diflubenzuron and triflumuron residues in greasy wool was developed by high performance liquid chromatography (HPLC) coupled with accelerated solvent extraction (ASE). The diflubenzuron and triflumuron residues were extracted with acetonitrile saturated with n-hexane at 80 degrees C and 10.34 MPa. The extract was pretreated by a series of procedures such as freezing-lipid filtration, concentration and purification by solid-phase extraction prior to the determination with HPLC. The target analytes were separated on a Waters Atlants dC18 column (250 mm x 4.6 mm, 5 microm), gradiently eluted with acetonitrile and water as the mobile phases and detected by a photodiode array detector (DAD) at 254 nm. The linear ranges were 0.1 - 10.0 mg/L. There were good linearity between the peak areas and concentrations in the linear range for the analytes, and the correlation coefficients of diflubenzuron and triflumuron were higher than 0.9999. The limits of quantification for diflubenzuron and triflumuron were 0.05 and 0.04 mg/kg (S/N > or = 10), respectively. The method is simple, rapid, sensitive and suitable for preliminary screening of diflubenzuron and triflumuron residues in greasy wool.

Susceptibilidade do besouro rola-bosta africano a reguladores de crescimento de insetos / Susceptibility of African dung beetle to insect growth regulators

Verificou-se a ação dos reguladores de crescimento de insetos (IGR), diflubenzuron e methoprene, sobre o besouro rola-bosta africano, Digitonthophagus gazella (Fabricius), um inimigo natural da mosca-dos-chifres, Haematobia irritans irritans (Linnaeus). Casais de besouros foram colocados em baldes contendo terra úmida e alimentados com fezes bovinas contendo 1, 0,5 ou 0,2ppm de diflubenzuron e 0,2ppm de methoprene. Os insetos e sua prole foram recuperados com o auxílio de armadilhas pitfall. Diflubenzuron e methoprene não afetaram a sobrevivência dos adultos inicialmente expostos, mas interferiram na produção de descendentes. Diflubenzuron, nas concentrações de 1 e 0,5ppm, também afetou a duração do ciclo de vida dos besouros. Nenhum dos IGRs alterou a razão sexual dos descendentes obtidos. As concentrações testadas de diflubenzuron mostraram-se moderadamente nocivas ao besouro enquanto methoprene a 0,2ppm mostrou ser pouco nocivo, segundo os critérios da International Organization for Biological Control.

The effects of insect growth regulators (IGR), diflubenzuron and methoprene, on African dung beetle, Digitonthophagus gazella (Fabricius), a natural enemy of the horn fly, Haematobia irritans irritans (Linnaeus), was studied. Beetles were placed in buckets partially filled with humid soil and were fed bovine feces containing 1, 0.5, or 0.2ppm diflubenzuron and 0.2ppm methoprene. Insects and their progenies were recovered by pitfall traps. Diflubenzuron and methoprene did not affect the survival of the adults but reduced their progenies. Diflubenzuron 1 and 0.5ppm also affected the life cicle of the beetles. None of the IGR modified the gender ratio of the progenies. According to the IOBC criteria, diflubenzuron tested concentrations showed to be moderately harmful to the beetles, whereas methoprene 0.2ppm was slightly harmful.

Determination of photoirradiated high polar benzoylureas in tomato by HPLC with luminol chemiluminescence detection.

This study reports the first analytical application of luminol chemiluminescence reaction for the sensitive detection of two benzoylurea insecticides (diflubenzuron and triflumuron). Off-line experiments demonstrated that previously irradiated traces of these benzoylurea insecticides largely enhanced the chemiluminescence emission yielded from the oxidation of luminol in methanol:water mixtures, by potassium permanganate in alkaline medium, the enhancement being proportional to the concentration of both pesticides. The two benzoylureas were determined in tomato samples by coupling liquid chromatography with post-column photoderivatization and detection based on this chemiluminescence reaction. Tomato samples were extracted using the QuEChERS method based on extraction with acetonitrile and dispersive solid-phase clean-up using primary and secondary amine (PSA). Interferences due to matrix effect were overcome by using matrix-matched standards. The optimised method was validated with respect to linearity, limits of detection and quantification, precision and accuracy. Under the optimised conditions, calibrations graphs were linear between 0.05 and 0.50 microg mL(-1) for diflubenzuron and between 0.10 and 1.00 microg mL(-1) for triflumuron. Method detection limits were 0.0025 and 0.0131 microg mL(-1) (equivalent to 0.0005 and 0.0026 mg kg(-1)) and quantification limits were 0.05 and 0.10 microg mL(-1) (equivalent to 0.01 and 0.02 mg kg(-1)) for diflubenzuron and triflumuron, respectively. In both cases, quantification limits were lower than the maximum residue levels (MRLs) established by the European legislation. The relative standard deviation of intra-day precision was below 10% and recoveries were between 79.7% and 94.2% for both pesticides.