Organophosphorus Pesticides In Water Samples Research Articles

3D graphene–carbon nanotubes-based solid-phase extraction technique combined with GC–MS for the determination of organophosphorus pesticides in water samples

Three-dimensional graphene–carbon nanotubes were prepared by the chemical reduction of a mixed aqueous solution of carboxylated multiwalled carbon nanotubes (C-MWCNTs) and graphene oxide, followed by freeze-drying. C-MWCNTs were then introduced into a three-dimensional graphene aerogel. The obtained three-dimensional graphene–carbon nanotubes were used as a solid-phase adsorbent for the determination of four organophosphorus pesticides (OPPs) in water using GC–MS. Under the optimal extraction conditions, good linearity was achieved between 0.5 and 500 μg L−1 with a correlation coefficient of 0.9993–0.9998. The limits of detection (S/N = 3) and limits of quantification (S/N = 10) for the OPPs ranged from 0.28 to 0.52 and 0.96 to 1.64 μg L−1, respectively. The accuracy of the proposed method was evaluated by measuring the recovery of spiked samples, which ranged from 94.8 to 103.5%, with relative standard deviations lower than 7.0% (n = 3). This method was applied to the determination of target analytes in wetland water, lake water, and river water, and the results showed that the three-dimensional graphene–carbon nanotubes have great potential for the determination of OPPs in real water samples.

An experimental design approach for the solid phase extraction of some organophosphorus pesticides from water samples with polymeric microbeads

The aim of this study was to develop a solid phase extraction (SPE) method for extraction of eleven organophosphorus pesticides (OPPs) from water samples before gas chromatography-mass spectrometry (GC-MS) analysis. The poly(divinylbenzene-N-methacryloyl-L-tryptophan methyl ester) [PDMAT] microbeads synthesized via suspension polymerization of N-methacryloyl-L-tryptophan methyl ester and divinylbenzene (DVB) were used as an adsorbent for SPE of dichlorvos, diazinon, disulfoton, parathion-methyl, malathion, fenthion, chlorpyrifos, bromophos-methyl, chlorfenvinphos, bromophos-ethyl and ethion. A central composite design (CCD), combined with Derringer's desirability function (DF) approach was used for evaluation and optimization of various parameters affecting the extraction efficiency, such as adsorbent amount (g), pH and elution rate of the solvent. The mean relative recoveries for OPPs from the water matrices ranged from 69 to 139% with intra-day RSD of 0.58–8.17% and inter-day relative standard deviation (RSD) of 0.60–4.94%. The PDMAT-SPE method had a good linearity at 1-50 µg L−1 (R2≥0.987) concentration range and a limit of detection (LOD) in the range of 0.002−0.118 µg L−1, with the exception of diazinon (0.597 µg L−1). The developed SPE method demonstrated that it could be applied for the determination of OPPs in water samples.

Chemical Vapour Deposition of MWCNT on Silica Coated Fe3O4 and Use of Response Surface Methodology for Optimizing the Extraction of Organophosphorus Pesticides from Water.

Multiwalled carbon nanotube (MWCNT) was fixed onto the surface of a magnetic silica (Fe3O4@SiO2) substrate via chemical vapour deposition (CVD). Acetylene gas was used as the carbon source and cobalt oxide as the catalyst. The chemical and physical characteristics of the materials were investigated by transmission electron microscopy (TEM), Raman spectroscopy (RS), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), and nitrogen adsorption/desorption isotherm. The synthesized Fe3O4@SiO2-MWCNT nanocomposite was used as a magnetic solid phase extraction (MSPE) adsorbent for the preconcentration of organophosphorus pesticides (OPPs), specifically, azinphos methyl, chlorpyrifos, parathion, and malathion. The factors influencing the extraction efficiency such as pH, contact time, and adsorbent dosage were investigated and optimized by response surface methodology (RSM) and desirability function. Linear response was obtained in the concentration range of 10–200 μg/L for the analytes with determination coefficients ranging between 0.9955 and 0.9977. The limits of detection (LODs) and quantification (LOQs) were in the range of 0.004-0.150 μg/L and 0.013-0.499 μg/L, respectively. Fe3O4@SiO2-MWCNT was applied in the extraction and subsequent determination of OPPs in water samples from Vaal River and Vaal Dam with recoveries ranging from 84.0 to 101.4% (RSDs = 3.8–9.6%, n = 3) in Vaal River and 86.2 to 93.8% (RSDs = 2.9–10.4%, n = 3) in Vaal Dam. The obtained results showed that the newly synthesized Fe3O4@SiO2-MWCNT nanocomposite can be an efficient adsorbent with good potential for the preconcentration and extraction of selected OPPs from aqueous media.

Determination of six organophosphorus pesticides in water samples by three-dimensional graphene aerogel-based solid-phase extraction combined with gas chromatography/mass spectrometry.

In the present study, a three-dimensional graphene aerogel (3D-GA), synthesised by chemical reduction of an aqueous solution of graphene oxides (GOs) with ethylenediaminethermal by a simple water bath method followed by freeze-drying treatment, was used for the solid-phase extraction (SPE) of six organophosphorus pesticides (OPPs) (i.e. trichlorfon, dimethoate, ethoprophos, parathion, fenitrothion and fenthion) from water samples. The target analytes were extracted using packed SPE cartridges and then eluted with tetrahydrofuran. The eluate was collected and dried with high-purity nitrogen gas at room temperature. After redissolving in acetone, the residue was analysed using gas chromatography/mass spectrometry (GC/MS). The proposed method demonstrated a good linearity between 0.5 and 500 μg L−1 with the correlation coefficient of 0.9990–0.9998. The limits of detection (LODs) (S/N = 3) and the limits of quantification (LOQs) (S/N = 10) for the six OPPs pesticides were in the range of 0.12–0.58 μg L−1 and 0.41–1.96 μg L−1, respectively. The accuracy of the present method was evaluated by measuring the recovery of the spiked samples, which ranged from 93.8% to 104.2% with relative standard deviations (RSDs) of 1.1–5.6%. The established method was successfully applied to the determination of the target analytes in environmental water samples including tap water, river water, drinking water and lake water, demonstrating its great potential for the determination of OPPs in water.

Coprecipitation-assisted coacervative extraction coupled to high-performance liquid chromatography: An approach for determining organophosphorus pesticides in water samples.

An analytical methodology based on coprecipitation-assisted coacervative extraction coupled to HPLC-UV was developed for determination of five organophosphorus pesticides (OPPs), including fenitrothion, guthion, parathion, methidathion, and chlorpyrifos, in water samples. It involves a green technique leading to an efficient and simple analytical methodology suitable for high-throughput analysis. Relevant physicochemical variables were studied and optimized on the analytical response of each OPP. Under optimized conditions, the resulting methodology was as follows: an aliquot of 9 mL of water sample was placed into a centrifuge tube and 0.5 mL sodium citrate 0.1 M, pH 4; 0.08 mL Al2 (SO4 )3 0.1 M; and 0.7 mL SDS 0.1 M were added and homogenized. After centrifugation the supernatant was discarded. A 700 μL aliquot of the coacervate-rich phase obtained was dissolved with 300 μL of methanol and 20 μL of the resulting solution was analyzed by HPLC-UV. The resulting LODs ranged within 0.7-2.5 ng/mL and the achieved RSD and recovery values were <8% (n = 3) and >81%, respectively. The proposed analytical methodology was successfully applied for the analysis of five OPPs in water samples for human consumption of different locations of Mendoza.

Ultrasound-assisted temperature-controlled ionic liquid dispersive liquid-phase microextraction combined with reversed-phase liquid chromatography for determination of organophosphorus pesticides in water samples.

A rapid and sensitive ultrasound-assisted temperature-controlled ionic liquid (IL) dispersive liquid-phase microextraction (UTILDLPME) combined with reversed-phase liquid chromatography-ultraviolet (RPLC-UV) was developed for the determination of five organophosphorus pesticides (OPPs; azinphos-methyl, chloropyriphos, parathion-methyl, diazinon, and phosalone) in water samples. Parameters including IL type, IL volume, ionic strength, sonication time, heating/cooling temperature, centrifugal time, and speed were investigated. The extraction procedure was induced by the formation of cloudy solution, which was composed of 75 μL of 1-butyl-3-methylimidazolium hexafluorophosphate ([C4MIM]PF6 ) dispersed entirely into 5 mL sample solution with the assistance of ultrasound for 3 min and temperature at 40°C. Under optimal conditions, linearity of the five OPPs was obtained in the range of 0.09-200 ng/mL with correlation coefficients of 0.998 or more. Limits of detection and limits of quantitation ranged from 0.01 to 0.1 ng/mL and from 0.05 to 0.4 ng/mL, respectively. Compared with conventional microextraction techniques, the proposed UTILDLPME exhibited the highest extraction efficiency ranging between 90 and 98% for targeted OPPs. Furthermore, the proposed UTILDLPME/RPLC was successfully applied to different water samples (tap, well, and lake water) showing relative recoveries ranging from 96.9 to 103.2%. Therefore, UTILDLPME/RPLC-UV could be a simple, rapid, sensitive, and efficient routine technique for determination of OPPs in water.

Ultrapreconcentration and determination of organophosphorus pesticides in water by solid-phase extraction combined with dispersive liquid-liquid microextraction and high-performance liquid chromatography.

Solid-phase extraction coupled with dispersive liquid-liquid microextraction was developed as an ultra-preconcentration method for the determination of four organophosphorus pesticides (isocarbophos, parathion-methyl, triazophos and fenitrothion) in water samples. The analytes considered in this study were rapidly extracted and concentrated from large volumes of aqueous solutions (100 mL) by solid-phase extraction coupled with dispersive liquid-liquid microextraction and then analyzed using high performance liquid chromatography. Experimental variables including type and volume of elution solvent, volume and flow rate of sample solution, salt concentration, type and volume of extraction solvent and sample solution pH were investigated for the solid-phase extraction coupled with dispersive liquid-liquid microextraction with these analytes, and the best results were obtained using methanol as eluent and ethylene chloride as extraction solvent. Under the optimal conditions, an exhaustive extraction for four analytes (recoveries >86.9%) and high enrichment factors were attained. The limits of detection were between 0.021 and 0.15 μg/L. The relative standard deviations for 0.5 μg/L of the pesticides in water were in the range of 1.9-6.8% (n = 5). The proposed strategy offered the advantages of simple operation, high enrichment factor and sensitivity and was successfully applied to the determination of four organophosphorus pesticides in water samples.

Extraction of organophosphorus pesticides by carbon-coated Fe3 O4 nanoparticles through response surface experimental design.

In this paper, carbon-coated Fe3 O4 nanoparticles were successfully synthesized and used as a magnetic solid-phase extraction absorbent for the preconcentration and extraction of organophosphorus pesticides in environmental water samples. The carbon-coated Fe3 O4 nanoparticles were characterized by transmission electron microscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, and vibrating sample magnetometry. The determination of organophosphorus pesticides in water samples with carbon-coated Fe3 O4 nanoparticles was investigated by high-performance liquid chromatography with a diode array detector. Furthermore, the response surface model based on the central composite design was applied to quantitatively investigate the effect of some important variables influencing the extraction efficiency, such as pH, treatment time, amount of nanoparticle sorbents, and amount of salt and to find the optimized conditions providing the highest extraction efficiency. Under optimized conditions, the calibration curve was linear in the range of 0.5-15.0 ng/mL with a regression coefficient of 0.9948, 0.9958, and 0.9931 for fenitrothion, diazinon, and ethion, respectively. The obtained results showed that this analytical method would be useful for the analysis of fenitrothion, diazinon, and ethion in tap water with high precision and accuracy.

Vortex-assisted liquid-liquid microextraction using a low-toxicity solvent for the determination of five organophosphorus pesticides in water samples by high-performance liquid chromatography.

Vortex-assisted liquid-liquid microextraction followed by high-performance liquid chromatography with UV detection was applied to determine Isocarbophos, Parathion-methyl, Triazophos, Phoxim and Chlorpyrifos-methyl in water samples. 1-Bromobutane was used as the extraction solvent, which has a higher density than water and low toxicity. Centrifugation and disperser solvent were not required in this microextraction procedure. The optimum extraction conditions for 15 mL water sample were: pH of the sample solution, 5; volume of the extraction solvent, 80 μL; vortex time, 2 min; salt addition, 0.5 g. Under the optimum conditions, enrichment factors ranging from 196 to 237 and limits of detection below 0.38 μg/L were obtained for the determination of target pesticides in water. Good linearities (r > 0.9992) were obtained within the range of 1-500 μg/L for all the compounds. The relative standard deviations were in the range of 1.62-2.86% and the recoveries of spiked samples ranged from 89.80 to 104.20%. The whole proposed methodology is simple, rapid, sensitive and environmentally friendly for determining traces of organophosphorus pesticides in the water samples.

Solidification of floating organic drop microextraction combined with gas chromatography-flame photometric detection for the analysis of organophosphorus pesticides in water samples

Vortex-assisted solidification of floating organic drop microextraction combined with GC-FPD for organophosphorus pesticide analysis in water samples.

Sol-Gel Hybrid Cyanopropyltriethoxysilane-methyltrimethoxysilane as Adsorbent for Dispersive-Micro Solid Phase Extraction of Selected Organophosphorus Pesticides in Water Samples

Commercial solid phase extraction (SPE) sorbents normally used for organophosphorus pesticides (OPPS) analysis is C18. However, it show low retention for polar compounds and is rather expensive. The limitations are overcome through the development of a new sol-gel hybrid material, cyanopropyltriethoxysilane-methyltrimethoxysilane (CNPrTEOS-MTMOS). Sol-gel hybrid CNPrTEOS-MTMOS was successfully synthesized and applied as an adsorbent for dispersive-micro-SPE (D-µ-SPE) of three selected OPPs from several water samples. Extracted analytes were analyzed using gas chromatography-mass spectrometry. Under the optimum conditions (100 mg CNPrTEOS-MTMOS as adsorbent, 10 mL water samples, 7 min extraction time, 300 µL methanol as desorption solvent and 3 min desorption time), the method showed excellent detection limits (0.01-0.004 µg L-1 at S/N = 3) and linear range achieved were 0.01-10 µg L-1. The CNPrTEOS-MTMOS sorbent offers an alternative sorbent material for the extraction of OPPs of various polarity. The developed D-µ-SPE method was successfully applied for the simultaneous analysis of OPPs in several water samples and results were compared with published results. Sol-gel hybrid CNPrTEOS-MTMOS showed high potential as an alternative adsorbent for D-µ-SPE technique for OPPs.

Sol-gel/nanoclay composite as a solid-phase microextraction fiber coating for the determination of organophosphorus pesticides in water samples.

A novel solid-phase microextraction (SPME) fiber coated with a sol-gel/nanoclay composite was prepared by the sol-gel technique involving the hydrolysis reaction of alkoxysilanes and the subsequent condensation reaction with hydroxyl groups of the nanoclay on a stainless steel wire. A method based on direct immersion SPME and gas chromatography-corona discharge ion mobility spectrometry was developed for the determination of four organophosphorus pesticides in aqueous samples. The effect of different experimental parameters on the extraction efficiency of the method was investigated. The sol-gel/nanoclay fiber showed higher extraction performance for the organophosphorus pesticides compared with Ppy/nanoclay, sol-gel coating, and three commercial fibers (polydimethylsiloxane (PDMS), PDMS/divinylbenzene (DVB), and polyacrylate (PA)). Limits of detection (LOD) and quantitation (LOQ) of the method were in the range of 0.003-0.012 and 0.01-0.02μgL(-1), respectively. The calibration curves were linear in a concentration range from 0.01 to 2.0μgL(-1) (r (2) > 0.995). The relative standard deviations for intra- and inter-day precision were 3.3-5.6 and 6.4-8.4%, respectively. Fiber-to-fiber reproducibility for three prepared fibers was 7.4-10.2%. Finally, the method was successfully applied for the extraction of the studied compounds from water samples. The relative recovery obtained for the spiked real-water samples were 86-104%.

Determination of organophosphorus pesticides in water samples by using a new sensitive luminescent probe of Eu (III) complex

This work describes the application of fluorescence for investigating the interactions of Eu(III)-TAN-1,10 phenanthroline (where TAN=4,4,4-Trifluoro-1-(2-naphthyl)-1,3-butanedione) with pesticides Chlorpyrifos, Malathion, Endosulfan, Heptachlor. The complex was synthesized and characterized by elemental analysis, FTIR, x-ray spectroscopy, solid fluorescence and thermal analysis. The results indicated that the composition of this complex is [Eu(TAN)2(Phen)(H2O)2]Cl. The luminescence properties of the complex in different solvents and at different pH values have been investigated. The results show that the complex exhibits more efficient luminescence at pH=7.5. The interactions of Eu-complex with different pesticides (Chlorpyrifos, Malathion, Endosulfan, and Heptachlor) in aqueous medium have been investigated by fluorescence measurements. The luminescence intensity of the probe is quenched by Malathion and enhanced by (Endosulfan, Heptachlor, and Chlorpyrifos). Direct methods for the determination of the pesticides under investigation have been developed using the luminescence variations of the probe in solution. The detection limits are 0.47, 1.02, 0.66, 0.64µmol/L for Chlorpyrifos, Endosulfan, Heptachlor, and Malathion, respectively. The binding constants and thermodynamic parameters of the pesticides with probe were evaluated. The emission quantum yield (QY=0.71) of Eu(III)-complex was determined using tris (2,2׳-bipyridyl) dichlororuthenium(II) hexahydrate. A thermodynamic analysis showed that the reaction is spontaneous with negative ΔG. Effect of some relevant interferents on the detection of pesticides has been investigated. The new method was applied to the determination of the pesticides in different types of water samples (tap, river, and waste water).

Ultrasound-Assisted Dispersive Liquid-Liquid Microextraction for Determination of Organophosphorus Pesticides in Water Samples by Gas Chromatography-Pulsed Flame Photometric Detection

Ultrasound-Assisted Dispersive Liquid-Liquid Microextraction for Determination of Organophosphorus Pesticides in Water Samples by Gas Chromatography-Pulsed Flame Photometric Detection

Vortex-assisted low density solvent based demulsified dispersive liquid–liquid microextraction and high-performance liquid chromatography for the determination of organophosphorus pesticides in water samples

A simple, rapid, effective and eco-friendly preconcentration method, vortex-assisted low density solvent based solvent demulsified dispersive liquid–liquid microextraction (VLDS–SD–DLLME), followed by high performance liquid chromatography–diode array detector (HPLC–DAD) analysis, has been developed for the first time for the determination of four organophosphorus pesticides (OPPs) (e.g., azinphos-methyl, parathion-methyl, fenitrothion and diazinon) in environmental water samples. In this preconcentration procedure, an emulsion was obtained after the mixture of extraction solvent (1-dodecanol) and dispersive solvent (acetonitrile, ACN) was injected rapidly into 10mL of the sample solution. The vortex agitator aided the dispersion of the extraction solvent into the sample solution. After the formation of an emulsion, the demulsifier (ACN) was added, resulting in the rapid separation of the mixture into two phases without centrifugation. Under optimal conditions, the proposed method provided high extraction efficiency (90–99%), good linearity range (0.5–500ngmL−1), low limits of detection (0.25–1ngmL−1) and good repeatability and recoveries were obtained.

Determination of Trace Organophosphorus Pesticides in Water Samples by Solid Phase Disk Extraction and Gas Chromatography-Thermionic Specific Detector

A simple, rapid, sensitive, and high-throughput method based on solid-phase disk extraction (SPDE) and a gas chromatography–thermionic specific detector (GC-TSD) is described for the determination of organophosphorus pesticides (OPPs) in water samples. The proposed SPDE sample pretreatment method was initially optimized and the optimum experimental conditions found were 500 mL water sample (pH 2.5–7.0) extracted and enriched by a C18 (octadecyl) solid phase extraction disk at flow rate of 5 to 50 mL/min and eluted by 5 mL of acetone and 3 × 5 mL methylene chloride. The linearity of the method ranged from 0.020 to 1.00 µg/L for dimethoate, methyl parathion, and malathion, with correlation coefficients ranging between 0.9976 and 0.9992. The concentration factors for OPPs were between 498 and 554. The limits of detection were in the ng/L level, ranging between 2.5 and 4 ng/L. The relative recoveries of spiked 3 OPPs (dimethoate, methyl parathion, and malathion) with external calibration method at different concentration levels in pure, fresh water, and sea water samples were 102–112%, 94–109%, and 99–104%, respectively, and with relative standard deviations of 4.1–6.2%, 3.4–4.6%, and 3.5–5.2% (n = 3), respectively. It is concluded that this method can be successfully applied for the determination of OPPs in pure water, fresh water, and sea water samples.

Ionic liquid-based solvent bar microextraction for determination of organophosphorus pesticides in water samples

In this article, a method of ionic liquid-based solvent bar microextraction combined with high performance liquid chromatography was developed to measure organophosphorus pesticides (OPPs) in water samples. The solvent bar microextraction was based on applying hydrophobic ionic liquid to the lumen and wall pores of a hollow fiber. The main factors influencing the extraction including types of ionic liquid, stirring speed, extraction time, extraction temperature, and salt effect were investigated. The proposed method was successfully applied in the analysis of real environmental water samples under the optimal extraction conditions and good spiked recoveries of 86.71–103.7% were obtained. The linear range was 1–200 μg L−1 and the detection limits were 0.015–0.026 μg L−1 for the four OPPs analyzed. These results demonstrated that solvent bar microextraction was a simple and accurate technique with a high enrichment factor.

Optimisation and application of dispersive liquid–liquid microextraction for simultaneous determination of carbamates and organophosphorus pesticides in waters

A very simple and sensitive method was developed for the simultaneous determination of carbamate and organophosphorus pesticides in water samples, using dispersive liquid–liquid microextraction (DLLME) coupled with gas chromatography-mass spectrometry (GC-MS). Carbofuran and chlorfenvinphos were used as model molecules in this study. The optimisation of some important DLLME parameters (type and volume of extraction and dispersive solvents, sample volume, extraction time, and use of NaCl) was performed using a design of experiments approach. Under optimised conditions of the DLLME methodology (500 μL of methanol, 80 μL of chlorobenzene, 10 mL of aqueous sample, 4 minutes of vortexing and no salt addition), the calibration curve was linear in the concentration range of 0.1–250 μg L−1 for carbofuran and 0.1–200 μg L−1 for chlorfenvinphos. The limits of detection (LODs) were 0.04 μg L−1 for the carbamate and 0.02 μg L−1 for the organophosphorus pesticide. The proposed method was successfully applied to the analysis in river, mineral and tap water samples, yielding satisfactory results.

Bamboo Charcoal as Solid-Phase Extraction Adsorbent for the Determination of Organophosphorus Pesticides in Water Samples by High-Performance Liquid Chromatography

In this paper, bamboo charcoal was successfully developed for the solid-phase extraction adsorbent for the determination of six organophosphorus pesticides in water samples. After the bamboo charcoal was pretreated and packed in the solid-phase extraction cartridge, the organophosphorus pesticides in water samples were carried out the solid-phase extraction. To establish a perfect solid-phase extraction procedure, the experimental conditions including the eluent, eluent volume, pH of the sample, flow rate of the sample, and loading volume of the sample were all investigated. When 100 mL water samples in the pH range of 6–7 were loaded with the flow rate of 2.5 mL · min−1 and then eluted with 10 mL acetonitrile, the proposed extraction method was validated by the recovery, correlation coefficient (R2), repeatability (RSD, n = 7) and LODs, which were 69.6–93.4%, 0.9982–0.9998, 2.9–5.6%, and 0.08–1.04 µg · L−1, respectively. Furthermore, the analysis of the tap, snow, and river water samples demonstrated the feasibility of the proposed SPE method for real water samples. Based on the aforementioned factors, it could be concluded that bamboo charcoal was a good solid-phase extraction adsorbent, and this proposed solid-phase extraction method was suitable for the effective enrichment and determination of the organophosphorus pesticides in water samples.

Nanophotocatalytic UV degradation system for organophosphorus pesticides in water samples and analysis by Kubista model

The photocatalytic degradation of organophosphorus pesticides like methyl parathion (MP) and parathion (PA), under UV irradiation is studied using synthesized Zinc oxide (ZnO) nanocatalyst. Two cases were considered for removal of organophosphorus (OP) pesticides such as only UV (i.e. direct photolysis) and UV–ZnO nanocrystal. The Langmuir–Hinshelwood (L–H) relationship between the initial rate and the initial concentration indicates that the reaction occurs with the adsorbed substrate. Factors affecting the kinetics of the process such as quantum yield, electrical energy per order (EEO), dosage of nanophotocatalyst and L–H model have been discussed. The optimal conditions for degradation were obtained using 85mgl−1 ZnO, 40% O2 (v/v) with rate constants L–H adsorption equilibrium constant (Kp=0.127 for MP and 0.122 for PA) and rate constant of surface reaction (Kc=0.212 for MP and 0.204 for PA). The kinetics of disappearance of OP pesticides (i.e. MP and PA) in water suspension using ZnO nanophotocatalyst illuminated at λ=253.7nm and examined. The quantum yield values for photodegradation of pesticides by photolysis and UV–ZnO process under the illumination of UV at 253.7nm is calculated as 0.00072, 0.012 for MP; 0.00068 and 0.01 for PA. The EEO values for degradation of pesticide by photolysis for UV–ZnO was found to be 20,006, 1392.4kWhm−3 for MP; 19,089 and 1387.2kWhm−3 for PA.