Uncertainty Evaluation of Preparation of Organophosphorus Pesticide Mixed Standard Solution

The uncertainty of standard solution plays an important role in detection of pesticide residues. It may affect the accuracy of detection results. In this study, the 14 organophosphorus pesticides mixed standard solution was used as the material to analyze all the influencing factors for the preparation of mixed standard solution with uncertainty as the only judging index. The preparation uncertainty of mixed standard solution was calculated with the top-down calculation method. In the end, the expanded uncertainty was presented. The results showed that the preparation of mixed standard solution from stock solution with precise pipettes had a relatively low uncertainty.

Comparison of Two Procedures for Extraction and Clean-up of Organophosphorus and Pyrethroid Pesticides in Sediment

Two procedures were compared for extraction and clean-up of 20organophosphorus and 19 pyrethroid pesticides in sediment to identify the more effective procedurefor groups of pesticides or individual compounds. In Procedure I, methanol/water and n-hexane wereused for extraction, and 1:10 (v/v) dichloromethane in n-hexane and acetone were used as eluents foreluting the analyte through the cartridge, with one evaporating steps on a rotary evaporator andtwo eluting steps on the cartridge. n-hexane/acetone (2:1, v/v) was used for extraction and elutionin Procedure II with one evaporating step on a rotary evaporator and one eluting step on thecartridge. All extractions were performed under an ultrasonic bath and gas chromatography and massspectrometry were utilized for measurements. Procedure II was developed as a rapid, timesaving, lesscostly and safer substitute for Procedure I which was an old method. Procedure II was moreeffective for almost all the organophosphorus pesticides tested and 11of the 19 pyrethroidpesticides, while Procedure I was more appropriate for analysis of 5 pyrethroid pesticides. However,recoveries of most pyrethroid pesticides were fairly low. Thus, further studies should focus onadjustment and formulation of solvents for more efficient extraction and clean-up of pyrethroidpesticides from sediment samples.

Organophosphorus Pesticide Extraction and Cleanup from Soils and Measurement Using GC-NPD

The objectives of this study were to optimize instrumental parameters and conditions for analysis of selected organop- hosphorus pesticides (OPPs) by gas chromatography (GC) with nitrogen-phosphorus detection (NPD) (GC-NPD); to select an appropriate solvent system; to conduct a comparison of sonication and shaking extractions; and to select an appropriate procedure for extracting organophosphorus pesticides from soils. Procedure I consisted of n-hexane or petroleum ether together with acetone used as solvents, while Procedure contained several solvents including acetone, methanol, dichloromethane, and n-hexane or petroleum ether. Experimental results indicated that a mixture of petroleum ether/acetone (2:1, v/v) could be used in place of n-hexane/acetone (2:1, v/v) as it was a less expensive solvent system. In addition, shaking under a water bath at 20 °C was more effective than sonication. Also, Procedure I was more effective, safer, and more timesaving than Procedure Procedure I was applied to three soil types of different organic matter content, with recoveries of the OPPs from the yellow-brown soils, which had a higher organic matter content, being lower than those from the yellow and red soils.

Computational interaction analysis of organophosphorus pesticides with different metabolic proteins in humans

Pesticides have the potential to leave harmful effects on humans, animals, other living organisms, and the environment. Several human metabolic proteins inhibited after exposure to organophosphorus pesticides absorbed through the skin, inhalation, eyes and oral mucosa, are most important targets for this interaction study. The crystal structure of five different proteins, PDBIDs： 3LII, 3NXU, 4GTU, 2XJ1 and 1YXA in Homo sapiens （H. sapiens）, interact with organophosphorus pesticides at the molecular level. The 3-D structures were found to be of good quality and validated through PROCHECK, ERRAT and ProSA servers. The results show that the binding energy is maximum -45.21 relative units of cytochrome P450 protein with phosmet pesticide. In terms of H-bonding, methyl parathion and parathion with acetylcholinesterase protein, parathion, methylparathion and phosmet with protein kinase C show the highest interaction. We conclude that these organophosphorus pesticides are more toxic and inhibit enzymatic activity by interrupting the metabolic pathways in H. sapiens.

Enzyme Inhibition Rate Method for Rapid Detection of Organophosphorus and Carbamate Pesticides in Cowpea

[Objectives ] The paper was to explore enzyme inhibition rate method for rapid detection of organophosphorus and carbamate pesticides in cowpea. [ Methods ] Acetylcholinesterase （ACHE） was added to cowpea extract, to determine the inhibition rate of extract against enzyme. The influences of different sampiing methods and sampling parts on detection results were compared. [ Results] The positive rate of standard sampling was 18.18% higher than that of non-stand- ard sampling, and the positive rate of samples collected from cowpea tail was 16.67% higher than that collected from other parts. [ Condmions] Enzyme inhibi- tion rate method is suitable for rapid detection of organophosphorus and carbamate pesticides in cowpea.

Carboxylic Esterase and Its Associations With Long-term Effects of Organophosphorus Pesticides

To examine a） the effect of organophosphorus pesticide exposure on activity of carboxylic esterases, namely butyrylcholinesterase （BChE）, carboxylesterase （CarbE） and paraoxonase （PonE）; and b） the association of polymorphisms of BChE and PonE with individual genetic susceptibility to organophosphorus pesticide exposure. Methods A cross-sectional study was conducted in 75 workers exposed to organophosphorus pesticides and 100 non-exposed controls. The serum activity of these enzymes was measured. Variant forms of BCHE-K, PON-192, and PON-55 were detected. A symptom score was developed as a proxy measure of clinical outcomes. Results Activities of both BChE and CarbE were lower in exposed workers （27.3±21.65 runol.hl.mL^-l and 235.6±104.03 nmol-min^-l.mL^-l） than in non-exposed workers （78.313±30.354 nmol.h^-l.mL^-1 and 362.681_＋194.997 nmol.min^-1.mL^-1）. The activity of PonE was not associated with exposure status. The AChE activity in the exposed workers with BCHE-K genotype UU （61 cases）, genotype UK （12 cases） and genotype KK （2 cases） was 105.05, 84.42 and 79.00 mmol-h^-1.mL^-1, respectively and the accumulative symptom scores were 3.74, 9.17, and 12.50 accordingly. The AChE activity in the exposed workers with PON-192 genotype BB （37）, genotype AB （27） and genotype AA （11） was 116.8, 91.2, and 72,3 mmol-h^-1.mL^-1, respectively and the symptom scores were 2.00, 6.74, and 9.73 accordingly. The AChE activity in those with PON-55 genotype LL （70） and genotype LM （5） was 102.4 and 82.8 mmol-h^-1.mL^-1 and the symptom scores were 4.53 and 9.20. The symptom score was the highest in individuals with abnormal homozygote for each of the three gene loci. Condusions Long-term exposure to organophosphorus pesticides can inhibit BChE and CarbE activity, but exerts no inhibitory effect on PonE activity. Different genotypes of BCHE-K, PON-192, and PON-55 may be related to the severity of adverse health effects of organophosphorus pesticide exposure. Implications of potentially higher susceptibility of workers with mutant homozygotes should be evaluated to reduce health risks.

Application of Current Hapten in the Production of Broad Specificity Antibodies Against Organophosphorus Pesticides

Diethylphosphono acetic acid （DPA） was used as a current hapten to generate broad specificity polycolonal antibodies against a group of organophosphorus pesticides. Six New Zealand white rabbits were immunized with immunogens synthesized by the active ester method （AEM） or 1-ethyl-3-（3-dimethylaminopropyl）-carbodimide method （EDC）. The titers of antisera reached 25 600 by AEM and 6 400 by EDC, respectively. Polyclonal antibodies raised against DPA were screened and selected for the competitive indirect enzyme-linked immunosorbent assay （CI-ELISA）. A CI-ELISA for DPA was developed with a detection limit of 3.536 ng mL^-1and an I50 value of 0.182 μg mL^-1. The assay specificity was evaluated by obtaining competitive curves for several structurally related compounds as competitors. The antiserum showed high affinities to chlorpyrifos, diazinon, omethoate, parathion-ethyl and profenofos with I50 of 0.12, 0.15, 0.21, 0.88, 0.97 and 2.5 μg mL^-1, respectively. The results indicate that the assay could be a screening tool for quantitation and semiquantitation determination of the above former five organophosphorus pesticides.

Recognition mechanism and sequence optimization of organophosphorus pesticides aptamers for better monitoring contaminations in food

Aptamers as a kind of biological recognition element have shown great potential in monitoring and the rapid quantification of organophosphorus pesticides(OPPs). However, molecules of OPPs are structurally similar and original aptamers selected by systematic evolution of ligands by exponential enrichment are usually long-chain bases, which hamper the further application under OPPs-aptamer recognition. The aim of the research was to develop a new strategy to design oligonucleotide sequences for binding OPPs by combination of experimental and molecular modeling methods. 3D models of aptamers binding OPPs were constructed, and binding energy and the most probable binding site for the OPPs were then determined by molecular docking, and the binding sites were further confirmed by the results of 2-AP replaced experiments. Based on the docking results, a new aptamer for detection 4 representative OPPs with only 29 bases was designed by reasonable truncation and mutation of the reported aptamer(named S4-29). The interaction between this new aptamer and OPPs were analyzed by molecular docking, microscale thermophoresis, circular dichroism and fluorometric analysis. The results revealed that the new aptamer exhibit more superior recognition performance to OPPs, which can be promote the monitoring ability of OPPs contaminations in food.

The degradation of organophosphorus pesticides by means of sodium percarbonate

The factors and mechanisms of oxidative degradation of three organophosphorus pesticides （dichlorvos, methamidophos and phoxim） were studied with sodium percarbonate （SPC） as a solid oxidant. The result showed that SPC has highly activity in degrading these organophosphous pesticides. The most efficient degradation of pesticides occurred under basic conditions and the degradation rates increased with time extension and high temperature. The degradation of organophosphorus pesticides was expected to get even better results at lower initial concentration. Furthermore, we analyzed the intermediate products by NMP, spectrometry. On the basis of the analytical result, the oxidative degradation mechanism was proposed for each organophosphous pesticide. It is significant to understand the environment chemistry of organophosphorus pesticides in environmental system.

The Influencing Factors of Disposable Acetylcholinesterase Biosensor for in Situ Detection of Organophosphorus Pesticide

An amperometric biosensor based on acetylcholinesterase (ACHE) is assembled by simple adsorption of the AChE on 7,7,8,8-tetracyanoquinodimethane (TCNQ) modified screen-printed electrodes.This biosensor is used to detect the inhibitory effect of organophosphorus pesticides on AChE activity.The detection of organophosphorus pesticides is done with acetylthiocboline chloride (ATCh) as substrate.In order to obtain the optimized response to substrate,the influencing factors of the biosensor are investigated,including temperature,pH,incubation time,substrate concentration and AChE concentration. The measurements were performed after inhibition by immersing the enzyme electrode into the parathion methyl solution. Under the optimized conditions,that is,500 U/ml AChE concentration,pH 7.2,10 min incubation time,2 mmol/L substrate concentration and temperature of 37℃,from 5×10^(-8) mol/L to 5×10^(-5) mol/L is close to linear (regression equation: y(%)=124.055+15.7991gx,R^2=0.99644),which corresponds to 8.7%～56.1% AChE inhibition.With the optimized conditions, the lowest detectable amount of parathion methyl is 13×10^(-9).

Study of multiresidue analytical method for organonitrogen and organophosphorus pesticides in soil and water

A gas chromatographic method without derivatization was developed for the residue analysis of 10 organonitrogen and 9 organophosphorus pesticides in soil and water. The samples were blended or shaken with acetone for extraction. The extracts were cleaned up by coagulation, then, re-extracted with three 50 ml portions of dichloromethane. The final residue was detected by gas chromatography equipped with NPD. All of the 19 pesticides were completely separated at a constant temperature. The method described above was applicable to the simultaneous determination of 10 organonitrogen and 9 organophosphorus pesticides .in soil and water with the satisfactory recovery (from 82.42% to 103.57%), coefficient of variance (from 0.17% to 12.57%) and limit of detection (from 0.0006 ppm to 0.058 ppm).

Separation of chlorinated hydrocarbons and organophosphorus, pyrethroid pesticides by silicagel fractionation chromatography and their simultaneous determination by GC-MS

A silicagel fractionation procedure for environmental sample extracts, which separates chlorinated hydrocarbons(CHCs) and organophosphorus, pyrethroid pesticides into two groups for subsequent instrumental analysis, was developed in this study. This method was achieved by optimizing the fraction cut-off volume of elution and different solvents. Using fully activated silica gel and cut-off CHCs collection after 10 ml 10% dichloromethane (DCM) in n-hexane passing through the column resulted in satisfactory separation of CHCs and organophosphorus, pyrethroid pesticides. This procedure had a higher reliability for CHCs than for organophosphorus, pyrethroid pesticides, because there is a relatively reliable recovery for CHCs. This approach is less expensive due to reducing sample pre-treatment time and solvent consumption.

Disposable Amperometric Acetylcholinesterase Biosensor for the Detection of Organophosphorus Pesticides

A rapid,simple,disposable and inexpensive acetylcholinesterase (ACHE) amperometric biosensor for the detection of organophosphorus pesticides was developed by simple adsorption of the enzyme on screen-printed electrodes.The biosensor consisted of an Ag/AgCl reference electrode and a graphite working electrode.The mixture of graphite and the 7,7,8,8-tetracyanoquinodimethane (TCNQ) was printed on electrodes.The detection of organophosphorus pesticides was done with acetylthiocholine chloride (ATCh) as substrate.The biosensor was used to detect the inhibitory effect of organophosphorus pesticides on AChE activity.The 1μl of enzyme solution containing 0.1 U AChE and 1% bovine serum albumin (BSA) were simply dropped on the working electrode surface.The biosensor operated at a potential of 300 mV vs. Ag/AgCl in a pH 7.2 0.1 mol/L phosphate buffer and 0.1 mol/L KCl.We obtained a calibration plot of the percentage inhibition versus the logarithm of parathion methyl concentration following an incubation time of 10 mix in parathion methyl solution. The lowest detectable amount of parathion methyl was 0.026 ppm.The amperometric biosensor based on acetylcholinesterase was disposable and low cost (about 1 yuan RMB).

Study on the toxic effect of the mixture of organophosphorus pesticide on perinatal rats

Objective To observe the toxic effect of the mixture of organophosphorus pesticide (MOP) on maternal rats and on the growth and development of their offspring. Methods Totally 40 Sprague-Dawley pregnant rats were randomly divided into three MOP dose groups and one control to which their offspring would be assigned. The experimental dosage of MOP and distilled water were administered orally starting on gestation day 15 and continued for 35 days. The physical development indices and the learning ability of F1 rats were measured during lactation. The pathological changes of uterus and liver of F0 rats were observed after weaning, while the weight ratio of uterus and some viscera to body of the F1 were examined. Results There were obvious changes of uterus and liver in the high-dose group of F0. The body-weight accretion of the F1 in high-dose group was obviously lower than that in control group (P<0.05). Some of the MOP F1 rats development indices delayed significantly (P<0.05), the learning ability decreased obviously, and the time of setting up memory prolonged (P<0.05). The ratio of the uterus weight to body-weight in the F1 MOP groups was significantly higher than that in control group (P<0.05). Conclusion The experiment doses of MOP are proved to have significant reproductive toxicity on perinatal rats.

Recent Advances in Degradation of Organophosphorus Pesticides

With the growing demand for environmental protection and physical health,food safety is now receiving more and more attention all over the world.However,pesticides are indispensable in agricultural production.Therefore,how to efficiently degrade pesticides and remove their residues in foods has always been a hot research topic in recent decades.This paper not only summarizes the types,degradation mechanism and artificial degradation of organophosphorus pesticides,but also highlights the latest advances in chemical degradation,photocatalytic degradation and biodegradation.

Toxicity of organophosphorus pesticide sumithion on larval stages of stinging catfish Heteropneustes fossilis

Sumithion is widely used to control brittle in paddy fields and tiger bug in fish larval rearing ponds. The objective of this study was to elucidate the toxic effects of sumithion on larval stages of stinging catfish Heteropneustes fossilis. Larvae were exposed to two concentrations(150 and 250 μg/L) of sumithion with one control in three replicates of each. Larvae samples were collected at 20- and 24-h intervals followed by observation under a digital microscope. Exposures of stinging catfish larvae to sumithion produced deformities including irregular head shape, lordosis, yolk sac edema, body arcuation, tissue ulceration, etc. The mortality rates of larvae were significantly increased in response to increase in sumithion concentrations. Furthermore, around 30% of the total adult stinging catfish reared in sumithiontreated aquaculture ponds were found to be deformed permanently. These findings highlight that exposure of stinging catfish to sumithion at the critical and sensitive stages in their life cycle may significantly reduce the number of returning adults. Therefore, the use of sumithion for crop protection needs to be considered carefully and alternatives to sumithion should to be developed for controlling aquatic insects in aqua-ponds during larval rearing.

Pressure Hydrolysis for Degradation of Omethoate Pesticide in Water

The effect of pressure on the hydrolysis rates and the degradation kinetics of environmentally persistent omethoate pesticide was studied. The results showed that the values of k obs increased and the values of activation volume (AV) decreased with increasing pressure. Among pH conditions (3.58, 6.01 and 8.5), pH 8. 5 was found to be the unstable condition and its half-life was reduced from 263 min at 1 atm to 19.37 min at 10 atm. These results describe that high-pressure hydrolysis is a useful technique for the conversion of toxic organic phosphorus into inorganic phosphorus. Key words pressure hydrolysis - organophosphorus pesticide - degradation

Pesticide Residue Content in Vegetable Bases of Lhasa City

[Objectives]To understand the quality safety of vegetables produced in vegetable planting bases around Lhasa City.[Methods]Four vegetable planting bases in the east,west,south,and north of Lhasa City were randomly selected for testing using rapid measuring instrument for agricultural residues and solid-phase microextraction-gas chromatography-mass spectrometer,with 120 vegetable samples selected.The testing samples included seven categories:green leafy vegetables,eggplants,melons,onions and garlic,root vegetables,beans,and fungi,totaling 29 types of vegetables.The samples were tested for 8 common prohibited and restricted pesticides in organic phosphorus and carbamate esters,including methamidophos,parathion,methyl parathion,monocrotophos,isocarbophos,methamidophos,aldicarb,and carbofuran.[Results]The pesticide inhibition rate of 6 kinds of vegetables detected by the rapid measuring instrument for agricultural residues was relatively high,with green leafy vegetables being the majority,reaching over 25%.By further establishing a solid-phase microextraction-gas chromatography-tandem mass spectrometry method,the accuracy of the data was verified experimentally.The experimental results indicated that the inhibition rate of vegetable samples in this experiment did not exceed 15%,and it was determined as a pollution-free vegetable.[Conclusions]According to the restriction standard of national pesticide use,the inhibition rate of vegetable samples was less than or equal to 40%,indicating that the quality of vegetables was qualified.

Nitrogen-doped carbon dots as efficient turn-on fluorescent probe for assay of organophosphorus pesticides

Concerns regarding human health and food safety have generated interest in developing simple,accurate,and cost-effective strategies for evaluating organophosphorus pesticide(OP)residues.In this study,nitrogen-doped carbon dots(N-CDs)were synthesized from a common low-cost precursor via a simple pyrolysis process.The fluorescence of the N-CDs can be suppressed by p-nitrophenol,which is the hydrolysis product of the p-nitrophenyl phosphate salt catalyzed by alkaline phosphatase(ALP).A fluorescent turn-on assay for the inhibitory effect of glyphosate was developed with a low detection limit and wide linear range.Moreover,the feasibility of visualizing OPs in vegetables was demonstrated by the fluorescence imaging of glyphosate on cabbage leaves.This research not only offers a facile method for the synthesis of highly fluorescent CDs but also inspires the development of effective multi-mode sensing platforms that include fluorescent testing and imaging for monitoring pesticide residues.