Determination Of Organophosphorus Pesticide Residues Research Articles

ZnO-rGO-based electrochemical biosensor for the detection of organophosphorus pesticides

The accurate determination of organophosphorus pesticide residues is of great importance for human disease monitoring and environmental safety. Numerous detection methods exist, among which sensitive monitoring of organophosphorus compounds using electrochemical sensors has gradually become a research hotspot. This paper used acetylcholinesterase (AChE) as an indicator anchored on a zinc oxide-reduced graphene oxide (ZnO-rGO) composite rich in active sites, in which green non-toxic zinc oxide (ZnO) nanomaterials were uniformly distributed on the reduced graphene for rapid detection of organophosphorus. The effects of different ratios of ZnO to reduced graphene on the performance of ZnO-rGO nanocomposites were investigated. The AChE/ZnO-rGO biosensor detects organophosphorus by electrochemical inhibition of acetylcholinesterase in the presence of organophosphorus. The developed electrochemical biosensor has high selectivity and good linearity, and the ZnO-rGO nanocomposite as a matrix for immobilization of acetylcholinesterase and detection of organophosphorus has the potential for highly sensitive pesticide detection.

Determination of organophosphorus pesticide residues in milk of cows and sheep by ultra-high-performance liquid chromatography- tandem mass spectrometry combined with passing type purification method

A method for the rapid determination of dichlorvos, trichlorfon, fenthion, fenthion-sulfone, fenthion-sulfoxide, fenthion-oxon, fenthion-oxon-sulfone, fenthion-oxon-sulfoxide, phoxim, propetamphos, malathion, diazinon and coumaphos 13 common organophosphorus pesticides and their metabolites poison residues in milk of cows and sheep by ultra-high-performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS) with passing type solid phase extraction(SPE) purification was developed. After centrifugation at 4 ℃, the milk was purified by passing type SPE with acetonitrile precipitating protein and determined by UPLC-MS/MS in electrospray positive ion mode(ESI+) and multi-reaction monitoring scanning(MRM), external standard method for quantitative analysis with matrix matching standard curve. The recoveries of 13 target compounds were between 81.5% and 107.5% and relative standard deviation was between 1.24% and 6.23% at three spiked levels of 5, 10, 20 μg/L. The detection limits of 13 target compounds were between 0.015 and 0.15 μg/L, and the quantitative limits were between 0.05 and 0.50 μg/L. No organophosphorus pesticide residues were detected in 20 samples of cows and sheep milk. The method has the advantages of good linear independence, low detection limit, high precision and accuracy, and can be used for daily monitoring of milk and related products.

On-line immobilized acetylcholinesterase microreactor based on capillary electrophoresis for the determination of organophosphorus pesticide residues

• Acetylcholinesterase is simply immobilized on the capillary via polydopamine coating. • The CE-based acetylcholinesterase microreactor is developed for the rapid detection of acephate. • The proposed method is capable to achieve rapid analysis of acephate with simple operation. In this study, a capillary electrophoresis-based online immobilized acetylcholinesterase (AChE) microreactor was developed for the determination of organophosphorus pesticide (OPs) residues in six fruit and vegetable juice samples. AChE was immobilized on the inner wall at the inlet of the capillary via polydopamine (PDA) coating. The immobilized AChE activity and other kinetic parameters were evaluated by measuring the peak area of the product (thiocholine). The value of Michaelis-Menten constant ( K m ) was determined to be 3.11 mM, and the half-maximal inhibitory concentration (IC 50 ) and inhibition constant ( K i ) of tacrine on immobilized AChE were measured to be 0.46 μM and 0.27 μM, respectively. The activity of the immobilized AChE remained more than 85.0% of its initial immobilized enzyme activity after 30 runs. Then, the developed strategy was successfully applied to detect the acephate in six fruit and vegetable juice samples (apple, pear, peach, tomato, cucumber and lettuce juice) with a limit of detection (LOD) of 11.0 ng/mL. Results show that the recovery of spiked samples are in the range of 86.0-96.0% with RSD of less than 5.7%. Therefore, the proposed method is capable of achieving rapid analysis of acephate with simple operation when there are no other types of OPs in the real samples.

Determination of Organophosphorus Pesticide Residues in Winter Bamboo Shoots by Homogenate Extraction Coupled with Gas Chromatography-Flame Photometric Detector

Excessive use of organophosphorus pesticides (OPPs) in fruits and vegetables may affect human health. In this paper, a simple, rapid and effective method for the determination of five OPPs in winter bamboo shoots by gas chromatography-flame photometric detector (GC-FPD) was developed. Three extractants and three extraction methods were examined respectively. The results showed that the recovery rate was higher when the samples were extracted by acetonitrile and treated with homogenate extraction method. Under the optimized conditions, recoveries ranged from 82.12% to 91.48% with the relative standard deviation (RSD) of 1.51-4.20% and the limit of detection (LOD) of 0.005-0.02 μg/mL. Results showed that using acetonitrile as extractants and homogenate extraction in sample preparation is an effective method in determination of pesticide residues in winter bamboo shoots.

Facile synthesis of a core-shell structured magnetic covalent organic framework for enrichment of organophosphorus pesticides in fruits

A facile strategy was developed for the fabrication of a magnetic covalent organic framework (COF) via grafting of the monomers, 2,5-dihydroxyterephthalaldehyde (Dt) and 1,3,5-tris(4-aminophenyl) benzene (Tb) onto surface-modified Fe3O4 nanoparticles. The magnetic COF, named as magnetic COF-DtTb, was readily fabricated without high temperature or harsh reaction conditions. The synthesized magnetic COF-DtTb nanoparticles were fully characterized, presenting a regular core-shell spherical structure, large specific surface area, superparamagnetism, and good thermal stability. Their potential as an enrichment adsorbent was investigated to establish an efficient magnetic solid-phase extraction method for the determination of organophosphorus pesticide residues in fruits. Systematic method validation revealed good linearity in the concentration range of 1–200 μg L−1 (correlation coefficient >0.9957). The method limits of detection were in the range of 0.002–0.063 μg kg−1, the method limit of quantification was 1.00 μg kg−1 and recoveries ranged from 72.8% to 111% with RSDs lower than 12.3%. The results indicated that magnetic COF-DtTb possesses superior trace enrichment properties for organophosphorus pesticides in fruits.

Liquid-phase microextraction of organophosphorus pesticides using supramolecular solvent as a carrier for ferrofluid

A liquid-phase microextraction based on application of supramolecular solvent as a carrier for ferrofluid has been developed for the extraction and determination of three organophosphorus pesticides (OPPs). The ferrofluid was produced from combination of oleic acid coated magnetic particles and supramolecular solvent as the extractant solvent. Ferrofluid can be attracted by a magnet, and no centrifugation step was needed for phase separation. A response surface methodology (RSM) based on central composite design (CCD) was used for efficient optimization of the main variables in the extraction procedure. Under the optimum experimental conditions, the calibration curves found to be linear in the range of 0.5–400µgL−1 with correlation coefficients ranging from 0.9967 to 0.9984. The intra-day and inter-day precision (RSD %) for 100 and 200µgL−1 of each pesticides were in the range of 2.0–5.3% and 2.6–5.7%, respectively. The limit of detection (S/N=3), ranged from 0.1 to 0.35μgL−1. The proposed method was successfully applied to the extraction and determination of organophosphorus pesticide residues in water and fruit juice samples.

Novel and rapid method for determination of organophosphorus pesticide residues in edible fungus using direct gas purge microsyringe extraction coupled on-line with gas chromatography–mass spectrometry

In this work a new analytical method for a rapid and simultaneous determination of 28 organophosphorus pesticides (OPPs) residues in edible fungus using gas purge microsyringe extraction (GP-MSE), coupled with on-line gas chromatography–mass spectrometry (GP-MSE-GC-MS) has been developed and optimized. GP-MSE, a novel gas flow liquid-phase microextraction technique, has been then fruitfully used as innovative and one-step extraction procedure, allowing a direct injection into the gas chromatograph coupled with a mass spectrometry detector (GC–MS) system without any further cleaning step. Once optimized, the GP-MSE-GC-MS analysis procedure showed reproducibility values, resolutions, linear responses, detection and quantification limits that allowed to consider this method suitable for the analysis of the 28 OPPs in real samples. Furthermore, OPP recoveries and the relative standard deviations (RSDs) ranged from 85.26% to 100.21%, and from 1.6% to 6.9%, respectively. This procedure was then used for the analysis of real samples and the obtained results were compared with those of ultrasonic extraction–solid phase extraction. Among the 28 OPPs, 14 of them were found in Lentinus edodes and Enoki mushrooms fungus samples, with a total concentrations of 112.7 and 210.7μgkg−1, respectively. This work demonstrated then that GP-MSE-GC-MS provided a highly efficient, solvent-saving, accurate and sensitive quantitative analysis method for a rapid determination of OPPs in edible fungus.

Determination of organophosphorus pesticide residues in vegetables using solid phase micro-extraction coupled with gas chromatography–flame photometric detector

An adequate and simple analytical method based on solid-phase microextraction (SPME) followed by gas chromatography–flame photometric detection (GC–FPD) for the determination of eleven organophosphorus pesticide residues (i.e., ethoprophos, sulfotep, diazinon, tolclofos-methyl, fenitrothion, chlorpyrifos, isofenphos, methidathion, ethion, triazophos, leptophos) in vegetables samples (cabbage, kale and mustard) was developed. Important parameters that influence the extraction efficiency (i.e., fibre type, extraction modes, extraction time, salt addition, desorption time and temperature) were systematically investigated. Four types of commercially available fibres (i.e., 50/30μm divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS), 65μm polydimethylsiloxane/divinylbenzene (PDMS/DVB), 100μm polydimethylsiloxane (PDMS), and 85μm polyacrylate (PA)) were evaluated. PA fibre exhibited the best performance and was used for the rest of the studies. The optimised extraction conditions were: extraction time, 30min at room temperature; stirring speed, 1275rpm; salt content, 10% NaCl; desorption time and temperature, 11min at 260°C; and no pH adjustment of the sample extract. The method was validated over the range 0.1–100μg/L. Repeatabilities were satisfactory, ranging between 2.44% and 17.9% for all analytes. The limits of detection and quantitation ranged from 0.01 to 0.14 and 0.03 to 0.42μg/L, respectively. The method was applied to twenty local vegetable (cabbage, kale and mustard) products. Chlorpyrifos (0.22–1.68μg/kg) was the most detected pesticide in the tested samples. The obtained values are however lower than the Maximum Residue Limits (MRLs) as stipulated in the Food Act & Regulations of Malaysia.

Application of graphene for the SPE clean-up of organophosphorus pesticides residues from apple juices

In this paper, an effective graphene-based SPE clean-up procedure coupled with GC-MS was developed for the determination of organophosphorus pesticide residues in apple juices. The apple juice samples were diluted with water and could be loaded onto the cartridge directly. Several parameters affecting the extraction efficiency were investigated, including the type of elution, washing solution, and sample pH. Under the optimized conditions, excellent limits of quantitation for the target analytes were found to be 0.15-1.18 ng/mL, and the average recoveries of the analytes at two spiked levels for real-sample analysis ranged from 69.8 to 106.2% with RSDs less than 7.3%. Furthermore, the graphene-based cartridges exhibited superior reusability for juice sample analysis. The proposed method is sensitive, simple, and cost saving, and provides a detection platform for the monitoring of pesticide residues.

LC-MS/MS Determination of Organophosphorus Pesticide Residues in Coconut Water

A simple and specific analytical method based on solid phase extraction (SPE), and liquid chromatography–electrospray ionization–tandem mass spectrometry (LC-ESI-MS/MS) operated in multipule reaction monitoring (MRM) mode with dynamic time segment acquisition windows, was developed to determine organophosphorus pesticide residues (acephate, monocrotophos, dimethoate, malaoxon, dichlorvos, malathion, phenthoate, parathion-ethyl, chlorfenvinfos, quinalphos, diazinon, phosalone, profenofos, ethion, chlorpyrifos) in tender coconut water. The method was observed to be linear with lower limit of detections ranged from 0.1 to 1.5 ng/mL (measured at S/N ratio 5:1) and limit of qunatitation 0.5 to 2.0 ng/mL (measured at S/N ratio 10:1) for all studied pesticides. The intra- and inter-day assay accuracies calculated at four concentration levels in six replicates (n = 6) were in the range of 80 % to 115 % with relative standard deviations (RSD) below 15 %. The percentage recoveries of all the analysed pesticides were in the range of 86.8 % to 107.6 % and the calculated RSD values were below 12 %. The developed method was applied to determine pesticide residues in natural tender coconut water samples. The results showed the presence of malathion ranging from 24 to 45 ng/L concentrations in some natural tender coconut water samples collected from various local market places in and around Hyderabad, Andhra Pradesh, India.

Determination of organophosphorus pesticide residues in vegetables by an enzyme inhibition method using α-naphthyl acetate esterase extracted from wheat flour

The widespread use of organophosphorus pesticides (OPs) poses a great threat to human health and has made the detection of OP residues in food an important task, especially in view of the fact that easy and rapid detection methods are needed. Because OPs have inhibitory effects on the activity of α-naphthyl acetate esterase (ANAE) in plants, in this work we evaluated the possibility of detecting OPs in vegetables with ANAE extracted from commercial flour. The limits of detection (LODs) obtained for methamidophos, dichlorvos, phoxim, dimethoate, and malathion in lettuce samples with crude ANAE were 0.17, 0.11, 0.11, 0.96, and 1.70 mg/kg, respectively. Based on the maximum residue limits (MRLs) for OPs in food stipulated by Chinese laws which are 0.05, 0.20, 0.05, 1.00, and 8.00 mg/kg for methamidophos, dichlorvos, phoxim, dimethoate, and malathion, respectively, the esterase inhibition method with crude ANAE had sufficient sensitivity to detect the residues of dichlorvos, dimethoate, and malathion in lettuce, but it could not be used to guarantee the safety of the same samples if methamidophos or phoxim residue was present. The sensitivity of the method was improved by the use of esterase purified by ammonium sulfate salting-out. The LODs obtained for methamidophos and phoxim with purified esterase were lower than the MRLs for these OPs in food. This is a very promising method for the detection of OP residues in vegetables using crude or purified esterase because of its cheapness, sensitivity, and convenience.

Development of a headspace solid-phase microextraction/gas chromatography–mass spectrometry method for determination of organophosphorus pesticide residues in cow milk

In the past few years, organophosphorus compounds become one of the most widely used classes of pesticides due to their acute toxicity against a wide variety of pests. In this work, a method based on solid-phase microextraction in mode headspace (HS-SPME) coupled to gas chromatography–mass spectrometry (GC–MS) was developed and optimized through multivariate factorial design to determine residues of organophosphorus pesticides in cow's milk. Different parameters of the method were evaluated, such as fiber type, temperature, extraction and desorption times, sample volume, effect of salt addition and stirring velocities. The evaluated pesticides were dichlorvos, sulfotep, demeton-S, dimpylate, disulfoton, parathion, methyl parathion, fenitrothion, chlorpyrifos and ethion. The best results were obtained using polydimethylsiloxane/divinylbenzene fiber and headspace mode at 90°C for 45min, along with stirring at 600rpm and desorption for 5min at 250°C. Under the optimized conditions, the proposed methodology was able to determine all of the pesticides with variation coefficients between 6.1% and 29.5%. Detection and quantification limits ranged from 2.16 to 10.85μgL−1 and from 6.5 to 32.9μgL−1, respectively. To evaluate residues of these pesticides in milk, cows were exposed to the pesticides of interest and milk was collected after 24h. The developed method was able to detect trace amounts of these pesticides in the collected milk samples.

Determination of organophosphorus pesticide residues in vegetables by gas chromatography using back-flush technique

The back-flush technique was used in the determination of organophosphorus pesticide residues in vegetables by gas chromatography. The pesticide residues were extracted with acetonitrile and sodium chloride under mechanical shaking, and separated by centrifuging and partitioning. The extract was analyzed by gas chromatograph equipped with a flame photometric detector and a micro fluidic device with back-flush function. The results showed that the 16 organophosphorus pesticides have good linearity within the concentration range of 0.040 -3.20 mg/L. The recoveries varied from 75.2% to 111.5%, with the relative standard deviations (RSDs) in the range of 2.8% - 10.4%. The detection limits of these target compounds were from 0.003 to 0.01 mg/kg. The application of back-flush technique in this method significantly reduced the cycle time and matrix effect and improved the analysis efficiency.

Determination of Organophosphorus Pesticide Residues in Vegetables by Electrokinetic Sequential Injection Analysis

A fast and convenient analysis method based on a plant esterase reaction inhibited by organophosphorus pesticides was developed for the determination of the pesticide residues in vegetable samples. The proposed method was performed with an electrokinetic sequential injection analysis (ESIA) system, which consisted of a spectrophotometer, a homemade electro‐osmosis pump, and four solenoid valves controlled by a Visual C program. The plant esterase extracted from fresh flour was adopted in the enzyme reaction. Several reaction parameters, such as the sample volume, the length of reaction coil, and the concentrations of reactants, are discussed in detail. The linear range of the calibration concentration was 0.03–0.5 µg/g dimethoate, which was used as a converted concentration of total organophosphorus pesticides. The detection limit of 0.01 µg/g dimethoate was achieved. The analytical throughput of the proposed method was about 24 samples per hour. The authors were invited to contribute this paper to a special issue of the journal entitled “Spectroscopy and Automation”. This special issue was organized by Miguel de la Guardia, Professor of Analytical Chemistry at Valencia University, Spain.

A rapid spectrophotometric assay of some organophosphorus pesticide residues in vegetable samples

A rapid and sensitive spectrophotometric method for the determination of some organophosphorus insecticides, i.e. malathion, dimethoate and phorate is described. It is based on the oxidation of organophosphorus pesticide with slight excess of N-bromosuccinimide (NBS) and the unconsumed NBS is determined with rhodamine B (lambda max: 550 nm). Beer's law is obeyed in the concentration range 0.108–1.08, 0.056–0.56 and 0.028–0.28 μg mL −1 for malathion, phorate and dimethoate, respectively. The method has been successfully applied for the determination of organophosphorus pesticide residues in various vegetable samples.

Determination of Organophosphorus Pesticide Residues in the Roots of Platycodon grandiflorum by Solid-Phase Extraction and Gas Chromatography with Flame Photometric Detection

A simple and rapid sample preparation method using accelerated solvent extraction and solid-phase extraction (SPE) cleanup for determining organophosphorus (OP) pesticides in the roots of Platycodon grandiflorum was developed. The OP pesticides were concentrated by use of an SPE cartridge (ENVI-Carb) and quantitatively analyzed and confirmed by capillary gas chromatography with flame photometric detection. The pesticides were eluted from the cartridges with 20 mL acetonitrile-toluene (3 + 1, v/v). The average recovery from 10 g PF grandiflorum roots, fortified at 3 levels ranging from 0.04 to 1.00 mg/kg, was 91.9% with a relative standard deviation of 4.3%. The limits of detection ranged from 1.16 x 10(-3) mg/kg (dimethoate) to 4.64 x 10(-3) mg/kg (dichlorvos). The proposed method showed acceptable accuracy and precision while minimizing environmental concerns, time, and labor.

Rapid GC-FPD determination of organophosphorus pesticide residues in Sicilian and Apulian olive oil

A simple and quick method for the determination of dimethoate, parathion-methyl, fenthion, parathion-ethyl, and methidathion in olive oil is described. Analysis was carried out using GC (capillary column 5 m × 0.32 mm × 0.45 μm) with aspecific detector (FPD), after sample extraction with acetonitrile. No cleanup was necessary because there were no interferences in the chromatogram. Recoveries of five pesticides at three fortification levels (1.0, 0.2 and 0.05 mg/kg) were in the range 78–97%. Seventy-nine samples were collected from Sicilian and Apulian individual growers during 2002–2003. Only 16% of the samples contained fenthion in concentrations ranging from 0.09 to 0.73 mg/kg; no other pesticides were detected in the 79 samples.

Optimization of high-performance liquid chromatography and solid-phase extraction for determination of organophosphorus pesticide residues in environmental samples

High-performance liquid chromatography with solid-phase extraction (HPLC-SPE) was optimized for the analysis of three organophosphorus pesticide residues in water, apples and vegetable samples. Octadecylsilica disks (47-mm diameter) were used for solid-phase extraction. The parameters that affect both separation and extraction of methyl parathion, parathion and phoxim, such as mobile-phase composition, ionic strength, temperature, pH, and breakthrough volume, were investigated. The application of optimized HPLC-SPE to environmental samples gave reproducible results with low detection limits of 5 µg L−1 for methyl parathion and parathion and 2.5 µgL−1. Precisions of less than 8, 9 and 12% were obtained for water, spinach and apple samples, respectively.

Determination of Organophosphorus Pesticide Residues in Onion and Welsh Onion by Gas Chromatography with Pulsed Flame Photometric Detector

A rapid gas chromatographic method for determining organophosphorus pesticide residues in allium such as onion and welsh onion containing high levels of sulfur-matrices was studied. A sample was extracted with acetonitrile and the acetonitrile layer separated by salting-out. The extract was cleaned up with gel permeation chromatography, and then with a tandem silica-gel/PSA mini-column. The test solution was subjected to gas chromatography with a pulsed flame photometric detector, Organophosphorus pesticide residues in such sulfurrich matrices were determined without any serious interfering peaks on the chromatograms by diluting the extracts 8-fold (0.25 g/ml of sample). No additional pretreatment to deactivate enzymes which caused interference was necessary. The rate of recovery of 36 organophosphorus pesticides from fortified onion and welsh onion ranged from 61 to 105% with the RSD usually < 10% for five experiments. The detection limits of these pesticides were good (0.002-0.01 mg/kg) for monitoring organophosphorus pesticide residues in agricultural products including allium, except for degradable trichlorfon. The method was applied to onion and welsh onion to demonstrate its use in routine analysis.

Determination of organophosphorus pesticide residues in Cilento (Campania, Italy) virgin olive oil by capillary gas chromatography

In this study, the occurrence of 18 organophosphorus pesticide residues in Cilento (Campania, Italy) virgin olive oil was investigated. Sixty-five samples were taken from the major production areas during 1999–2000. In 31 samples, nine organophosphorus pesticides, namely azinphos-ethyl, chlorpyrifos-methyl, diazinon, dimethoate, fenthion, formothion, methidathion, parathion and parathion-methyl were found in concentrations ranging from 0.030 to 0.120 mg/kg. Acefate, carbophenothion, chlorpyrifos, malaoxon, malathion, methamidophos, omethoate, paraoxon-methyl, and pirimiphos-methyl were not detected in any sample. Analysis was carried out using capillary gas chromatography with a Nitrogen/Phosphorus Detector (NPD) detector, after sample extraction with n-hexane and clean-up by a single-step multi-cartridge system. Recoveries of 18 pesticides at three fortification levels (0.5, 1.0 and 2.5 mg/kg) were in the range 82–110%. Only two samples contained dimethoate residue that exceeded the FAO/WHO Codex Alimentarius maximum residue limits (MRLs).