Determination Of Dichlorvos Research Articles

Determination of Dichlorvos in Pears by Surface-Enhanced Raman Scattering (SERS) with Catalysis by Platinum Coated Gold Nanoparticles

A surface-enhanced Raman scattering (SERS) sensor is reported for the determination of dichlorvos, an organophosphate pesticide (OP), in pears. Platinum coated gold nanoparticles (Au@PtNPs) were used as secondary catalysts to provide signal amplification. Acetylcholinesterase (AChE) catalyzed the hydrolysis of acetylthiocholine to form thiocholine. Thiocholine causes the accumulation of Au@PtNPs, which changes the particle size and prevents their peroxidase-mimicking activity. Dynamic light scattering was used to characterize the particle size. Following the addition of dichlorvos, the AChE activity was inhibited, the production of thiocholine and aggregation were reduced, and the peroxidase mimicing property was retained. In the presence of 3,3′,5,5′-tetramethylbenzidine (TMB), a blue product was produced that provided strong SERS signals. The SERS method showed a linear relationship for dichlorvos concentrations from 20 to 2000 µg/L. The developed protocol had a limit of detection of 20 µg/L. This SERS sensor assay was successfully applied for the quantification of dichlorvos in pears with satisfactory recoveries from 80.25 to 94.86%.

Magnetic-nanoparticles-based fluorescent immunoassay for individual and simultaneous determination of dichlorvos and paraoxon in milk

ABSTRACT A sensitive and rapid magnetic-nanoparticles-based fluorescent immunoassay (MNPs-FIA) for individual and simultaneous determination of dichlorvos (DDVP) and paraoxon in untreated raw milk was developed. The conjugates DDVP–cBSA (cationized bovine serum albumin) and paraoxon–BSA (bovine serum albumin) were labeled by fluorescent dyes. The optimal amount of immobilized polyclonal anti-DDVP and anti-paraoxon antibodies on MNPs (0.375 mg Ab-MNPs) and optimal concentrations of DDVP–cBSA–FITC (18 µg/mL) and paraoxon–BSA–FITC (22 µg/mL) for MNPs-FIA were determined. The calibration curves of individual and simultaneous immunoassays of DDVP and paraoxon were investigated. The IC50 value of the individual paraoxon assay in raw cow’s milk was 60 ng/mL and linear range 2–300 ng/mL. The IC50 value of the individual DDVP assay was 70 ng/mL and linear range 5–300 ng/mL. The IC50 values of the paraoxon and DDVP (100 and 120 ng/mL respectively) in simultaneous assay were higher than those of the individual ones, and their linear ranges were 10–400 ng/mL.

Preparation of Polyclonal Antibodies with Application for an Organophosphorus Pesticide Immunoassay

ABSTRACTHaptens of dichlorvos and paraoxon were conjugated to the carrier proteins of bovine serum albumin. The obtained conjugates were characterized by infrared and ultraviolet–visible spectroscopy. The binding ratios of dichlorvos and paraoxon-to-carrier proteins were also evaluated. The number of hapten molecules per protein molecule of dichlorvos–cationized bovine serum albumin conjugate was higher than for paraoxon–bovine serum albumin conjugate. The sheep polyclonal antibodies were produced against the dichlorvos and paraoxon. New multipolyclonal antibodies were obtained and characterized following the immunization of a 1:1 mixture of the immunogens for the simultaneous determination of dichlorvos and paraoxon by the immunoassay. An indirect enzyme-linked immunosorbent assay was used to characterize the reactivity of the antibodies to hapten conjugates. The multiantibodies showed lower affinities than the separate antibodies, but their affinities were sufficient for an immunoassay for the simultaneous determination of the analytes. The detection limit and linear range for the determination of dichlorvos and paraoxon alone and together were determined. The recovery was characterized to determine dichlorvos and paraoxon fortified in model solutions and milk. These results demonstrate the potential of this immunoassay for the quantitative screening of dichlorvos and paraoxon.

Paper-based chromatographic chemiluminescence chip for the detection of dichlorvos in vegetables

Paper chromatography was a big breakthrough in the early of 20th century but it is rarely used due to the long separation time and the diffusion on the sample spots. In this work, for the first time, a paper-based chemiluminescence (CL) analytical device combined with paper chromatography was developed for the determination of dichlorvos (DDV) in vegetables without complicated sample pretreatment. The paper chromatography separation procedure can be accomplished in 12min on a paper support (0.8×7.0cm2) by using 5µL sample spotted on it. After sample developing, the detection area (0.8×1.0cm2) was cut and inserted between two layers of water-impermeable single-sided adhesive tapes. The paper-based chip was made by attaching the middle layer of paper onto the bottom layer. Then it was covered by another tape layer, which was patterned by the cutting method to form a square hole (0.8×1.0cm2) in it. 10μL mixed solution of luminol and H2O2 was dropped on the detection area to produce CL. A linear relationship was obtained between the CL intensity and the concentrations of DDV in the range between 10.0ngmL−1 and 1.0μgmL−1and the detection limit was 3.6ngmL−1. Water-soluble metal ions and vitamins can be developed at different spatial locations relative to DDV, eliminating interference with DDV during detection. The paper-based chromatographic chip can be successfully used for the determination of DDV without complicated sample preparation in vegetables. This study should, therefore, be suitable for rapid and sensitive detection of trace levels of organophosphate pesticides in environmental and food samples.

Rapid and Accurate Determination of Dichlorvos in Water by Liquid Chromatography‐Electrospray Ionization‐Tandem Mass Spectrometry

An LC‐MS/MS method has been developed and validated for the determination of dichlorvos in ground and surface waters. The aqueous samples (20.0 mL) are led through a silica‐based C8+WAX mixed‐mode SPE cartridges. Such a step successfully eliminates humic substances and other interferences that induce a matrix effect. Since the recovery of dichlorvos is 100% and the matrix effect is eliminated, the calibration standards prepared in DI water can be used for accurate and rapid determination of dichlorvos in various aqueous samples. The quantification limit is 0.01 µg/L.

Determination of dichlorvos by on-line microwave-assisted extraction coupled to headspace solid-phase microextraction and gas chromatography–electron-capture detection

The pretreatment technique of microwave-assisted extraction on-line headspace solid-phase microextraction (MAE–HS-SPME) was designed and studied for one-step in-situ sample preparation prior to the chromatographic analysis of a pesticide on vegetables. The pesticide on chopped vegetables was extracted into an aqueous solution with the aid of microwave irradiation and then directly onto the SPME fiber in headspace. After being collected on to the SPME fiber and desorbed in the GC injection port, the pesticide (dichlorvos) was analyzed with a GC–electron-capture detection system. The optimum conditions for obtaining extraction efficiency, such as the pH, the polarity modifier, and the salt added in sample solution, the microwave irradiation, as well as the desorption parameters were investigated. Experimental results indicated that the proposed MAE–HS-SPME technique attained the best extraction efficiency of 106% recovery under the optimized conditions, i.e. irradiation of extraction solution (10% aqueous ethylene glycol) at pH 5.0 with medium microwave power for 10 min. Desorption at 220 °C for 3 min offered the best detection result. The detection was linear at 5–75 μg/l with correlation coefficient of 0.9985. Detection limit was obtained at ∼1.0 μg/l level based on S/N=3. The proposed method provided a very simple, fast, and solvent-less procedure to collect pesticides directly from vegetables for GC determination. Its application was illustrated by the analysis of trace dichlorvos in vegetables.

Determination of Dichlorvos, Trichlorfon and Their Metabolites and Degradation Products in Environmental Water, Drinks and Human Urine.

A systematic analytical procedure for dichlorvos (DDVP) and trichlorfon (DEP), organophosphorus pesticides, and furthermore for desmethyl dichlorvos (DM-DDVP), desmethyl trichlorfon (DM-DEP), dimethyl phosphate (DMP) and monomethyl phosphate (MMP), their metabolites and degradation products, was investigated. From the environmental water, drinks and human urine, after salting-out, only DDVP was first extracted with n-hexane and then the others were extracted with acetonitrile-diethylether (1 : 1, v/v) at about 1N by HCl. TLC was performed on silica-gel plate using acetonitrile-water (85 : 15, v/v) and isopropanol-water-28% ammonium hydroxide (75 : 24 : 1, v/v) as development systems. By colorations with 4-(p-nitrobenzyl) pyridine (NBP) and o-tolidine, they were relatively well detected. It was possible to determine DEP, DM-DDVP, DM-DEP, DMP and MMP by FID-GC and GC-MS after trimethylsilyl derivatization of them with N, O-bis (trimethylsilyl) trifluoroacetamide (BSTFA). The detection limits of their aqueous solution were 0.1-3 μg/ml by FID-GC and 0.2-10 μg/ml by scanning mode GC-MS. The coefficients of variation for their spiked urine sample by GC analysis in this way were 2.7-7.6% at 50μg/ml, respectively.

GLC Determination of Dichlorvos in Milk, Eggs, and Various Body Tissues of Cattle and Chickens

Abstract A gas chromatograph equipped with a flame photometric detector provided a highly sensitive method of determining residues of dichlorvos in milk, eggs, and various body tissues of cattle and chickens. Extraction and cleanup makes possible the detection of 0.003 ppm dichlorvos in milk and 0.002 ppm in body tissues and eggs. Recoveries of 79–87% are obtained from fat, muscle, and chicken skin, 93–97% from milk, and 77% from eggs.