Development of fenitrothion adsorbing recombinant Escherichia coli by cell surface display of pesticide-binding peptide.

In this study, constructed Escherichia coli could efficiently adsorb fenitrothion by displaying a pesticide-binding peptide on it using the anchoring motif OmpC. A codon-optimized, pesticide-binding peptide was attached to the C-terminus of OmpC at loop 7 (993 bp). The efficiency of fenitrothion binding by the monomer peptide was evaluated under different temperatures, pH levels, and fenitrothion concentrations. To enhance fenitrothion adsorption, a dimer of pesticide-binding peptide was also constructed and displayed. Compared with the peptide monomer, the dimer-displaying strain showed superior fenitrothion-binding ability. The performance of the strains was evaluated in artificial polluted soil, and their morphology was analyzed by FE-SEM. The results showed that these two kinds of constructed strains can adsorb fenitrothion in contaminated environments with no cellular activity reduction. ARTICLE INFO.

Analytical Methodology for Trace Determination of Propoxur and Fenitrothion Pesticide Residues by Decanoic Acid Modified Magnetic Nanoparticles.

A sensitive, rapid, reliable, and easily applicable method based on magnetic solid phase extraction (MSPE) combined with HPLC-PDA was developed for monitoring propoxur (PRO) and fenitrothion (FEN) pesticides in environmental water samples. The effect of major experimental variables on the extraction efficiency of both the pesticides was investigated and optimized systematically. For this purpose, a new magnetic material containing decanoic acid on the surface of particles was synthesized and characterized by XRD, FT-IR, SEM, EDX, and TGA analysis in detail. The simultaneous determination of pesticide molecules was carried out by using a Luna Omega C18 column, isocratic elution of acetonitrile (ACN): Water (70:30 v/v) with a flow rate of 1.2 mL min-1. After MSPE, the linear range for pesticide molecules (r2 > 0.9982) was obtained in the range of 5-800 and 10-800 ng mL-1, respectively. The limit of detections (LOD) are 1.43 and 4.71 ng mL-1 for PRO and FEN, respectively while RSDs % are below 3.5%. The applicability of the proposed method in four different environmental samples were also investigated using a standard addition-recovery procedure. Average recoveries at two spiking levels were over the range of 91.3-102.5% with RSD < 5.0% (n = 3). The obtained results show that decanoic acid grafted magnetic particles in MSPE combined with HPLC-PDA is a fast and simple method for the determination of PRO and FEN in environmental water samples.

Temperature-controlled liquid-liquid microextraction combined with high-performance liquid chromatography for the simultaneous determination of diazinon and fenitrothion in water and fruit juice samples.

A simple, environmentally benign, and rapid method based on temperature-controlled liquid-liquid microextraction using a deep eutectic solvent was developed for the simultaneous extraction/preconcentration of diazinon and fenitrothion. The method involved the addition of deep eutectic solvent to the aqueous sample followed by heating the mixture in a 75°C water bath until the solvent was completely dissolved in the aqueous phase. Then, the resultant solution was cooled in an ice bath and a cloudy solution was formed. Afterward, the mixture was centrifuged and the enriched deep eutectic solvent phase was analyzed by high-performance liquid chromatography with ultraviolet detection for quantification of the analytes. The factors affecting the extraction efficiency were optimized. Under the optimized extraction conditions, the limits of detection for diazinon and fenitrothion were 0.3 and 0.15 µg/L, respectively. The calibration curves for diazinon and fenitrothion exhibited linearity in the concentration range of 1-100 and 0.5-100 µg/L, respectively. The relative standard deviations for five replicate measurements at 10.0 µg/L level of analytes were less than 2.8 and 4.5% for intra- and interday assays, respectively. The developed method was successfully applied to the determination of diazinon and fenitrothion in water and fruit juice samples.

Vortex-assisted low density solvent liquid-liquid microextraction and salt-induced demulsification coupled to high performance liquid chromatography for the determination of five organophosphorus pesticide residues in fruits.

A simple and rapid microextraction method, vortex-assisted low density solvent liquid-liquid microextraction and salt-induced demulsification (VLLME-SID) coupled to high performance liquid chromatography (HPLC) was developed for the determination of organophosphorus pesticide (OPP) residues in fruits. The studied OPPs were azinphos-methyl, parathion-methyl, fenitrothion, diazinon and chlorpyrifos. For VLLME-SID, a mixture of low density solvents (1-dodecanol and hexane) was used as the extraction solvent under vortex agitation for enhancing dispersion. After complete dispersion, the emulsion was formed and the OPPs were extracted into extraction solvent droplets. Then, the emulsion was quickly broken up into two clear phases after the addition of AlCl3 as a demulsifier. Centrifugation was not required in this procedure. Under the optimal conditions, high enrichment factors (180-282), low limit of detections (LODs) (0.05-1 ng mL(-1)) and good precision (RSD≤7% for retention time and peak area) were obtained. The proposed method was successfully applied to the analysis of OPP residues in fruit samples (watermelon, grape, and cantaloupe). The LODs for samples were in the range 0.0006-0.0015 mg kg(-1) which are below the established EU-MRLs (0.01-0.3 mg kg(-1)). Good recoveries were also obtained (80-104%).

A selective molecularly imprinted polymer-solid phase extraction for the determination of fenitrothion in tomatoes.

A new and selective sorbent for molecularly imprinted solid-phase extraction (MISPE) was developed and applied for the determination of residues of fenitrothion (FNT) in tomatoes, using HPLC coupled to photodiode array detection (HPLC-DAD). Using FNT as the template molecule, methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the cross-linker, toluene as the porogenic solvent, and bulk polymerization as the synthetic method, a molecularly imprinted polymer (MIP) was synthesized. In order to choose the medium which promotes the best molecular recognition of FNT by the MIP, the adsorption of FNT by the MIP was studied in different media containing acetonitrile and toluene. Besides FNT, three structurally related compounds were used to evaluate the selectivity of the FNT-molecularly imprinted polymer. The MIP exhibited the highest selective rebinding to FNT. The method developed was validated, using fortified blank tomato samples. The extraction efficiency was 96%. The limits of detection and quantitation were 0.050 and 0.130 microg g(-1), respectively. The intra-day precision was 5.9% and the inter-day precision 8.1%. The accuracy was higher than 89% for a concentration level around the maximum residue limit of 0.5 microg g(-1).

Study of the mechanism of Flavobacterium sp. for hydrolyzing organophosphate pesticides.

The biotransformation by Flavobacterium sp. of the following organophosphate pesticides was experimentally and theoretically studied: phorate, tetrachlorvinphos, methyl-parathion, terbufos, trichloronate, ethoprophos, phosphamidon, fenitrothion, dimethoate and DEF. The Flavobacterium sp. ATCC 27551 strain bearing the organophosphate-degradation gene was used. Bacteria were incubated in the presence of each pesticide for a duration of 7 days. Parent pesticides were identified and quantified by means of a gas-chromatography mass spectrum system. Activity was considered as the amount (micromol) of each pesticide degraded by Flavobacterium sp. Also, structural parameters obtained by means of the CAChe program package for biomolecules, the reactivity index of phosphorus, of oxygen at the P = O function and of sulfur at the P = S function, and lipophilicity (log Poct) (ALOGPS v. 2.0) were obtained for each pesticide. Pesticides were hydrolyzed at the bond between phosphorous and the heteroatom, producing phosphoric acid and three metabolites. Enzymatic activity was significantly explained by the following multiple linear relationship: Enzymatic activity = 162.2 - 9.5(dihedral angle energy) - 25.0(Total energy) - 0.51(Molecular weight). Finally, a mechanism of Flavobacterium sp. to hydrolyze pesticides was proposed.