Fe3 O4 nanoparticles coated with polyhedral oligomeric silsesquioxanes and ß-cyclodextrin for magnetic solid-phase extraction of carbaryl and carbofuran.

In this study, porous sandwich structure Fe3 O4 nanoparticles coated by polyhedral oligomeric silsesquioxanes and ß-cyclodextrin were prepared by surface polymerization and were used as the magnetic solid phase extraction adsorbent for the extraction and determination of carbaryl and carbofuran. The Fe3 O4 nanoparticles coated with polyhedral oligomeric silsesquioxanes and ß-cyclodextrin were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, vibrating sample magnetometry, and scanning electron microscopy. After optimizing the extraction conditions, a method that combined magnetic solid phase extraction with high-performance liquid chromatography was developed for the determination of carbaryl and carbofuran in apple. The method exhibited a good linearity in the range of 2-400 µg/kg for carbaryl and carbofuran (R2  = 0.9995), respectively. The limits of detection were 0.5 µg/kg of carbaryl and 0.7 µg/kg for carbofuran in apple, respectively. Extraction recoveries ranged from 94.2 to 103.1% with the preconcentration factor of 300 and the relative standard deviations were less than 5.9%. These results indicated that the method combined magnetic solid phase extraction with high-performance liquid chromatography and was promising for the determination of carbaryl and carbofuran at trace amounts.

Preparation and characterization of magnetic molecular imprinted polymers with ionic liquid for the extraction of carbaryl in food.

Magnetic molecular imprinted polymers with ionic liquid used as an auxiliary solvent (IL@MMIPs) for the recognition of the methyl carbamate pesticide carbaryl (CBR) in foodstuff have been synthesized. The properties and application of IL@MMIPs were determined. The kinetic and isotherm adsorption processes were found to follow the pseudo-second-order and the Scatchard models, respectively. The selective experiment showed that the IL@MMIPs exhibited good selectivity to CBR compared to magnetic nonimprinted polymers with IL (IL@MNIPs). By using the IL@MMIPs as an adsorbent for the enrichment of CBR in food samples, the limit of detection (LOD, S/N = 3) and the limit of quantitation (LOQ, S/N = 10) of this method were 3 µg kg-1 and 10 µg kg-1, respectively. Compared with the traditional method, the IL@MMIP method has better recoveries (83.23-99.83%), precision (1.12-2.09%), and stabilization (intraday, 1.08-2.81%; interday, 2.26-3.30%). IL@MMIPs are an ideal adsorbent that could be applied to conveniently detect CBR in complex food, and the proposed method can be considered as a selective and sensitive alternative to traditional methods with affordable cost, avoiding the complex pretreatment procedure. Graphical abstract .

The effectiveness of chemical solutions on the removal of carbaryl residues from cucumber and chili presoaked in carbaryl using the HPLC technique.

This research aimed to compare the efficiency of five washing solutions (0.9% NaCl, 0.1% NaHCO3, DI water, 0.001% KMnO4, and 0.1% acetic acid) for removing carbaryl residues from cucumber and chili. The vegetables were soaked in 10 mg/L of carbaryl solution for 30 min and then washed for 30 min in one of the five washing solutions and the results compared. Each experiment was performed in triplicate and the amounts of carbaryl residues remaining were determined using high-performance liquid chromatography (HPLC). The results showed that 0.001% KMnO4 was the most effective at removing carbaryl from both vegetables. Washing with 0.001% KMnO4 reduced carbaryl residues to 64% and 28%, respectively, of the original concentrations. Washing with DI water was the least effective method of removing carbaryl residues. Hopefully, the results will encourage further research, into reducing carbaryl contamination by washing with chemical solutions, which will enable producers to reduce pesticide residues.

N-methylcarbamate pesticides and their phenolic degradation products: hydrolytic decay, sequestration and metal complexation studies.

We report on the rates of decomposition of a group of N-methylcarbamate (NMC) pesticides (carbaryl, carbofuran and propoxur) under pre-determined tropical field conditions. Rates of decomposition for three NMCs were determined at pH 7.08 and T = 20 °C and pH 7.70 and T = 33 °C respectively, as follows: carbaryl (78 days and 69 days); carbofuran (143 days and 83 days) and propoxur (116 days and 79 days). Investigation on methods for removal of NMCs and their phenolic decomposition products shows that activated charcoal outperforms zeolite, alumina, diatomaceous earth, cellulose and montmorillonite clay in the removal of both NMCs and phenols from aqueous solution. Furthermore, metal complexation studies on the NMCs and phenols showed that Fe (III) forms a complex with isopropoxyphenol (IPP) within which the Fe:IPP ratio is 1:3, indicative of the formation of a metal chelate complex with the formula Fe(IPP)3.

Carbaryl degradation by bacterial isolates from a soil ecosystem of the Gaza Strip

Abstract Carbaryl is an important and widely used insecticide that pollutes soil and water systems. Bacteria from the local soil ecosystem of the Gaza Strip capable of utilizing carbaryl as the sole source of carbon and nitrogen were isolated and identified as belonging to Bacillus, Morganella, Pseudomonas, Aeromonas and Corynebacterium genera. Carbaryl biodegradation by Bacillus, Morganella and Corynebacterium isolates was analyzed in minimal liquid media supplemented with carbaryl as the only source of carbon and nitrogen. Bacillus and Morganella exhibited 94.6% and 87.3% carbaryl degradation, respectively, while Corynebacterium showed only moderate carbaryl degradation at 48.8%. These results indicate that bacterial isolates from a local soil ecosystem in the Gaza Strip are able to degrade carbaryl and can be used to decrease the risk of environmental contamination by this insecticide.

Development of Fluorescence Sensing Material Based on CdSe/ZnS Quantum Dots and Molecularly Imprinted Polymer for the Detection of Carbaryl in Rice and Chinese Cabbage.

A fluorescence sensing material based on quantum dots with excellent optical properties and molecularly imprinted polymer (QDs@MIP) with specific recognition has been developed. First the surface of CdSe/ZnS QDs was modified with ionic liquids (ILs) by electrostatic interaction. The fluorescence sensing material was constructed from anchoring the MIP layer on IL modified CdSe/ZnS QDs by copolymerization, which had been developed for the detection of carbaryl in rice and Chinese cabbage. The MIP fluorescence was more strongly quenched by carbaryl than the non-imprinted polymer (NIP) fluorescence, which indicated that the QDs@MIP could selectively recognize the corresponding carbaryl. Furthermore, the developed QDs@MIP method was validated by HPLC and ELISA respectively, and the results of these methods were well correlated (R(2) = 0.98). The fluorescence sensing material had obvious advantages, such as being easily prepared and having specific recognition and photostability. The developed method was simple and effective for the detection of carbaryl. And, it could also provide the technical support for the rapid detection in food safety fields.

Determination of N-methylcarbamate insecticides in water samples using dispersive liquid-liquid microextraction and HPLC with the aid of experimental design and desirability function.

A rapid and simple method for the extraction and preconcentration of N-methylcarbamates (NMCs) (carbofuran, carbaryl and promecarb) in water samples using dispersive liquid-liquid microextraction (DLLME) using chemometrics was developed. Influence variables such as volume of extracting (CHCl(3)) and dispersing solvents (ACN), pH and ionic strength, extraction time and centrifugation time and speed were screened in a 2(7-4) Plackett-Burman design was investigated. The significant variables were optimized by using a central composite design (CCD) combined with desirability function (DF). At optimum conditions values of variables set as 126 µL chloroform, 1.5 mL acetonitrile, 1 min extraction time, 10 min centrifugation at 4000 rpm min(-1), natural pH, 4.7% (w/v) NaCl, the separation was reached in less than 14 min using a C(18) column and an isocratic binary mobile phase (acetonitrile: water (50:50, v/v)) with flow rate of 1.0 mL min(-1). At optimum conditions method has linear response over 0.001-10 µg mL(-1) with detection limit between 0.0001 and 0.0005 µg mL(-1) with relative standard deviations (RSDs) in the range 2.18-5.06% (n=6).

A greener and highly sensitive flow-based procedure for carbaryl determination exploiting long pathlength spectrophotometry and photochemical waste degradation.

An environmentally friendly analytical procedure with high sensitivity for determination of carbaryl pesticide in natural waters was developed. The flow system was designed with solenoid micro-pumps in order to improve mixing conditions and minimize reagent consumption as well as waste generation. A long pathlength (100 cm) flow cell based on a liquid core waveguide (LCW) was employed to increase the sensitivity in detection of the indophenol formed from the reaction between carbaryl and p-aminophenol (PAP). A clean-up step based on cloud-point extraction was explored to remove the interfering organic matter, avoiding the use of toxic organic solvents. A linear response was observed within the range 5-200 microg L(-1) and the detection limit, coefficient of variation and sampling rate were estimated as 1.7 microg L(-1) (99.7% confidence level), 0.7% (n=20) and 55 determinations per hour, respectively. The reagents consumption was 1.9 microg of PAP and 5.7 microg of potassium metaperiodate, with volume of 2.6 mL of effluent per determination. The proposed procedure was selective for the determination of carbaryl, without interference from other carbamate pesticides. Recoveries within 84% and 104% were estimated for carbaryl spiked to water samples and the results obtained were also in agreement with those found by a batch spectrophotometric procedure at the 95% confidence level. The waste of the analytical procedure was treated with potassium persulphate and ultraviolet irradiation, yielding a colorless residue and a decrease of 94% of total organic carbon. In addition, the residue after treatment was not toxic for Vibrio fischeri bacteria.

Application of dispersive liquid-liquid microextraction for the analysis of triazophos and carbaryl pesticides in water and fruit juice samples.

In this work, a simple, rapid and sensitive sample pretreatment technique, dispersive liquid-liquid microextraction (DLLME) coupled with high performance liquid chromatography-fluorescence detection (HPLC-FLD), has been developed to determine carbamate (carbaryl) and organophosphorus (triazophos) pesticide residues in water and fruit juice samples. Parameters, affecting the DLLME performance such as the kind and volume of extraction and dispersive solvents, extraction time and salt concentration, were studied and optimized. Under the optimum extraction conditions (extraction solvent: tetrachloroethane, 15.0 microL; dispersive solvent: acetonitrile, 1.0 mL; no addition of salt and extraction time below 5s), the performance of the proposed method was evaluated. The enrichment factors for the carbaryl and triazophos were 87.3 and 275.6, respectively. The linearity was obtained in the concentration range of 0.1-1000 ng mL(-1) with correlation coefficients from 0.9991 to 0.9999. The limits of detection (LODs), based on signal-to-noise ratio (S/N) of 3, ranged from 12.3 to 16.0 pg mL(-1). The relative standard deviations (RSDs, for 10 ng mL(-1) of carbaryl and 20 ng mL(-1) of triazophos) varied from 1.38% to 2.74% (n=6). The environmental water (at the fortified level of 1.0 ng mL(-1)) and fruit juice samples (at the fortified level of 1.0 and 5.0 ng mL(-1)) were successfully analyzed by the proposed method, and the relative recoveries of them were in the range of 80.4-114.2%, 89.8-117.9% and 86.3-105.3%, respectively.

Comparison of the biotransformation of the 14C-labelled insecticide carbaryl by non-transformed and human CYP1A1-, CYP1A2-, and CYP3A4-transgenic cell cultures of Nicotiana tabacum.

Transgenic tobacco-cell-suspension cultures expressing separately the human cytochrome P450 monooxygenases CYP1A1, CYP1A2, and CYP3A4 were utilized to study the biotransformation of the 14C-labelled insecticide carbaryl (=naphthalen-1-yl methylcarbamate). The resulting data were compared to similar data from the corresponding non-transformed (NT) tobacco-cell culture and commercially available membrane preparations (Bactosomes) of genetically modified bacteria separately containing the same human P450s. A rapid conversion rate of carbaryl was observed with the CYP1A1 and CYP1A2 cells, where only 49.7 and 0.2% of applied carbaryl (1 mg/l), respectively, remained after 24 h, as compared to 77.7% in the non-transformed culture. Unexpectedly, the corresponding results obtained from the CYP3A4 cultures were not definite. With 25 mg/l of carbaryl and 96 h of incubation, it was proven that the insecticide is also substrate of CYP3A4. This finding was supported by GC/EI-MS analysis of the primary metabolite pattern produced by the isozyme. This consisted of naphthalene-1-ol, N-(hydroxymethyl)carbaryl, 4-hydroxycarbaryl, and 5-hydroxycarbaryl, whereas the main product in non-transformed cells was N-(hydroxymethyl)carbaryl. Data obtained from the CYP1A1, CYP1A2, or CYP3A4 Bactosomes agreed with those of the P450-transgenic tobacco cells. Problems with GC/EI-MS analysis of carbaryl and its metabolites are discussed.

Application of dual counter-current chromatography for rapid sample preparation of N-methylcarbamate pesticides in vegetable oil and citrus fruit.

Dual counter-current chromatography (dual CCC) has been successfully applied to rapid sample preparation for the simultaneous determination of residual carbaryl, fenobucarb and methomyl in vegetable oil and citrus fruit. The citrus fruit samples were extracted with n-hexane solution containing stable isotopically labeled internal standards (methomyl-d3, fenobucarb-d3 and carbaryl-d9), and applied to dual CCC using a two-phase solvent system of n-hexane-acetonitrile to purify the carbamate pesticides from aliphatic sample matrix. The coiled column was rotated at 420 rpm, the lower mobile phase was introduced through the head toward the tail, and the upper mobile phase in the opposite direction. Due to the high partition efficiency of dual CCC, the lower phase fraction collected from 2 to 5 min after injection could be subjected to flow-injection tandem mass spectrometry directly after concentration. Repetitive sample injection can be performed at high reproducibility without a risk of contamination from the compounds retained in the column.

Genotoxicity of pesticide waste contaminated soil and its leachate.

OBJECTIVE: Improper land disposal of hazardous waste can result in leaching of hazardous constituents which may contaminate ground and surface water leading to adverse impact on human health and environment consequences. The present study utilized mammalian cell culture for the genotoxicity assessment of waste and its leachate. METHODS: Genotoxic potential and chemical analysis of pesticide derived tarry waste contaminated soil extract and its leachate was assessed using in vitro human lymphocyte cultures and GC-MS. RESULTS: The investigation revealed that the soil extract could cause significant to highly significant genotoxicity in the form of DNA strand break at 25 microL (P < 0.01), 50 microL, 100 microL and 200 microL (P < 0.001) and chromosomal aberration at 25 microL (P < 0.01) and 50 microL and 100 microL (P < 0.001). The leachate could cause significant DNA strand break and chromosomal aberration only at 100 microL and 200 microL (P < 0.01) dose levels. CONCLUSION: The genotoxicity observed is attributed to carbaril and tetra methyl naphthyl carbamate, the major ingredients of the extracts, as revealed by GC-MS.

Reductive degradation of carbaryl in water by zero-valent iron.

Reduction of carbaryl solution by zero-valent iron powder (ZVIP) was studied in a rotator batch system (70 rpm) in order to evaluate the utility of this reaction in remediation of carbamate contaminated water. Degradation with different amount of ZVIP: 0.01, 0.02, 0.03, 0.04 g/ml at pH 6.6 and at ambient temperature was investigated. The results show that the process exhibits a degradation rate appearing to be directly proportional to the surface contact area of ZVIP (325-mesh) with the carbaryl molecules. Three analytical techniques were used to monitor carbaryl degradation: (1) A UV-Vis diode array spectrophotometer was used to record all spectra. (2) A high performance liquid chromatography was used to separate by-products and examine the evolution of breakdown products. (3) A home-built spectrophosphorimeter that uses the solid surface room temperature phosphorescence (SSRTP) was employed to observe selectively the decline of the carbaryl concentration at different amount of ZVIP on Whatman no. 1 filter paper. Results show that the reducing degradation of carbaryl with ZVIP as the source of electrons is effective with a half-life close to several minutes.

Carbaryl washoff from soybean plants.

Both the efficacy and fate of most foliar-applied pesticides may be affected by weather variables, especially rain. A multiple-intensity rainfall simulator was used to determine the effects of rainfall intensity and amount on concentrations of carbaryl (Sevin(R) XLS Plus) washed from soybean plants. Two hours after carbaryl was applied at 1.12 kg/ha, 25 mm of rain was applied at intensities of 13.0, 27.4, 53.8, or 105.1 mm/h. About 67% of the carbaryl on the plants was washed off by 25 mm of rain. Rainfall intensity affected carbaryl concentrations in washoff; higher concentrations occurred at lower intensities. Even though the experimental conditions were designed for "worst-case" conditions, washoff patterns suggested improved carbaryl rainfastness when compared to carbaryl (formulated as a wettable powder) washoff from cotton plants in earlier studies. Rainfall amount had a greater effect on carbaryl concentrations in washoff than rainfall intensity.