Pesticides In Environmental Waters Research Articles

Ultrasonic-induced grafted lanthanum sulfide decorated multi-walled carbon nanotube onto bacterial cellulose applied for adsorption of pesticides in environmental waters

A new biosorbent was fabricated by modification of bacterial cellulose biopolymer grafted with lanthanum sulfide decorated carboxylated multiwall carbon nanotube (La2S3@MWCNT@BC). The sorbent was employed in a green alternative dispersive-solid phase extraction of a variety of 14 pesticides in environmental water samples. The analyses were performed using GC-µECD. The properties and structure of La2S3@MWCNT@BC nanocomposite were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and adsorption-desorption isotherms. The composition of the sorbent was also investigated to evaluate the adsorptive properties of its constituents. The impact of various parameters influencing extraction efficacies such as sorbent dose, adsorption time, sample pH, ionic strength, and desorption conditions was investigated. The method was validated by specificity, matrix effect % (-0.4 to -7.4), enrichment factor (4–10), limits of quantification (0.007–0.31 μg L−1), matrix-matched calibration linearity (0.01–200 µg L−1), determination coefficients (r2=0.9921–0.9998), and precision. The optimized method was applied for the analysis of multiclass pesticides in seven environmental and drinking waters and the recoveries were obtained in the 81–108 % range with RSDs of 2.5–4.7 %. This paper is the first report on the synthesis and use of La2S3@MWCNT@BC nanocomposite to extract pesticides from different water samples. The greenness of the procedure was evaluated by the AGREE protocols.

Post-modified linker functionalization of metal organic frameworks for high-efficiency adsorption and quantification of trace organophosphorus pesticides in environmental water

Water pollution caused by organophosphorus pesticides (OPPs) from agricultural production causes vital great threat to mankind lives and thus developing a method for rapid removal and detection of OPPs is urgent. In this work, we proposed the linker functionalization of metal organic frameworks (UiO-66) by post-modification to generate defects and active sites for tailoring their adsorption behavior. The metal organic frameworks (MOFs) modified by functional groups (amino and pyridine) exhibited similar physicochemical property and pore structure. The UiO-66-PA exhibited an excellent performance of rapid adsorption of OPPs in water with average capacity of 246.55 mg/g. Experimental characterizations and theoretical simulations revealed that the enhanced binding energy between UiO-66-PA and OPPs resulted from synergistic interaction between pyridine and OPPs via nucleophilic effect, π-π interaction, and metal electronic interaction, boosting the adsorption capacity and removal efficiency, which suggested that functional group plays important role in improving performance. When used it as adsorbent for analysis of OPPs in water coupled with ambient ionization source, UiO-66-PA exhibited an excellent performance of the quantitative detection of OPPs in water with limit of detections (LODs) of 0.076–––0.251 ng/mL and relative standard deviations (RSDs) of 1.13 % − 5.84 %. In addition, the proposed analytical method could be applied in analysis of three environmental water samples with great sensitivity, anti-interference and reusability, which demonstrated that UiO-66-PA afforded outstanding selectivity for OPPs and could be appropriate for high-throughput screening and on-site analysis. This work could provide a novel method to design MOFs-based adsorbents with functions of removal and purification via post-modification and exhibit a great potential to rapid analysis of OPPs in environmental water.

A MnO2 nanosheet-mediated CRISPR/Cas12a system for the detection of organophosphorus pesticides in environmental water.

Nowadays, easy, convenient, and sensitive sensing strategies are still critical for organophosphorus pesticides in environmental water samples. Herein, a novel organophosphorus pesticide (OP) assay based on acetylcholinesterase (AChE) and a MnO2 nanosheet-mediated CRISPR/Cas12a reaction is reported. The single-strand DNA (ssDNA) activator of CRISPR/Cas12a was simply adsorbed on the MnO2 nanosheets as the nanoswitches of the assay. In the absence of target OPs, AChE hydrolyzed acetylcholine (ATCh) to thiocholine (TCh), which reduced the MnO2 nanosheets to Mn2+, resulting in the release of the activator followed by activation of the CRISPR/Cas12a system. The activated Cas12a thereafter nonspecifically cleaved the FAM/BHQ1-labeled ssDNA (FQ-reporter), producing a fluorescence signal. Upon the addition of target OPs, the hydrolysis of ATCh by AChE was inhibited owing to OPs combining with AChE, and thus effective quantification of OPs could be achieved by measuring the fluorescence changes of the system. As a proof of concept, dichlorvos (DDVP) was chosen as a model OP analyte to address the feasibility of the proposed method. Attributed to the excellent trans-cleavage activity of Cas12a, the fluorescent biosensor exhibits a satisfactory limit of detection (LOD) for DDVP at 0.135 ng mL-1. In addition, the excellent recoveries for the detection of DDVP in environmental water samples demonstrate the applicability of the proposed assay in real sample research.

Development and validation of a GC × GC-ToFMS method for the quantification of pesticides in environmental waters

Water is a fundamental resource for living things, which is why its control is necessary. The widespread use of pesticides for agricultural and non-agricultural purposes has resulted in the presence of their residues in surface water and groundwater resources. Their presence in water is regulated through different directives, such as the Groundwater Directive, the Drinking Water Directive, and the Water Framework Directive, modified later several times, setting a maximum concentration of 0.1 µg.L−1 for individual pesticides and their degradation products, and 0.5 µg.L−1 for total pesticide residues present in a sample. There are different kinds of pesticides (e.g., organophosphorus and organochlorine pesticides, triazines, chloroacetamides, triazoles, (thio)carbamates) that have diverse chemical structures. Their determination and monitoring in a single analytical procedure are possible through multiresidue methods. In this study, 53 pesticides belonging to different chemical classes and their metabolites were selected based on their local occurrence and investigated in surface water and groundwater from agricultural areas susceptible to pesticide contamination. The methodology consisted of a classical solid-phase extraction (SPE) for the purification and enrichment of the pesticides, with a subsequent analysis in multidimensional gas chromatography coupled to mass spectrometry (GC×GC-MS). The quantification method was validated according to the Eurachem Guide in terms of linearity, precision, accuracy, limit of detection, and limit of quantification. After validation, the method was applied to 34 real-world water samples, and the results were compared with those obtained by a GC-QMS routine method.

An ultrastable 2D covalent organic framework coating for headspace solid-phase microextraction of organochlorine pesticides in environmental water

Herein, a quinoline-linked ultrastable 2D covalent organic framework (COF-CN) coated fiber was successfully prepared and used for highly-sensitive headspace solid-phase microextraction (HS-SPME) of organochlorine pesticides (OCPs) in environmental water. The extraction efficiency of the COF-CN coating for all 14 OCPs was higher than that of four commercial SPME fiber coatings and most of the published works, with enrichment factors ranging from 540 to 5065. In combination with gas chromatography-tandem mass spectrometry (GC-MS/MS), a wide linear range (0.05–200 ng/L), low detection limits (LODs, 0.0010–13.54 ng/L) and satisfactory reproducibility and repeatability were obtained under optimal conditions. Compared with the published works, the LODs of the developed technique were improved 2–5.9 times, and the enrichment factors (EFs) of the developed method were enhanced at least 2 times. The COF-CN coated fiber can be easily recycled and reused at least 70 times without any washing step. The adsorption mechanism was first characterized by density functional theory calculations and X-ray photoelectron spectroscopy analysis. Besides, the established method was successfully applied to the analysis of the distribution of trace OCPs in real water samples from Henan Province. All these results proved the promising application of the developed HS-SPME-GC-MS/MS method for organic pollutants analysis in water samples.

Pre-concentration of 218 multiclass pesticide in groundwater samples using MSU-1 mesoporous sorbent

A mesoporous material (MSU-1), prepared in the laboratory, was applied as a solid phase sorbent to pre-concentrate 218 multiclass pesticides in environmental waters. The pesticides present in the sample extracts were determined by ultra-high-performance liquid chromatography coupled with tandem mass spectrometry. The most intense ion was selected as precursor ion. After fragmentation in the collision chamber, the most intense transition (SRM1) was used for quantification and three points were used for identification and confirmation, as established by Directive 96/23/EC. A comprehensive study of the main variables affecting the sorption/desorption of pesticides in the MSU-1 was performed using step-by-step (elution solvent, sample pH and salt content) and multi-response surface (sorbent amount, water volume and solvent elution volume) methodologies, with the optimal values being no addition of NaCl, 100 mg MSU-1 sorbent, 50 mL water sample at pH = 6 and elution of pesticides with 5 mL of acetonitrile. The matrix effect was tested by comparing the slopes of solvent-based and matrix-matched calibration graphs. 80 % of pesticides showed a low matrix effect, and 20 % showed a medium or high matrix effect. Two calibration strategies were tested to correct the matrix effect by adding the pesticide standards before or after the pre-concentration step. The first one corrected for systematic errors due to the low adsorption of pesticides in the MSU-1 and corrected for the matrix effect. The method was validated using blank groundwater samples spiked with 0.1, 0.25 and 0.5 μg/L of all pesticides. Recoveries between 54 and 130 % (RSD ≤ 20 %) were obtained for most pesticides (90 %), while recoveries ≥ 130 % were obtained for 22, 10 and 5 pesticides at 0.1, 0.25 μg/L and 0.5 μg/L, respectively. A monitoring study of thirteen groundwater samples collected in Almería (South of Spain) was performed applying the proposed methodology. Thirty-eight different pesticides were found in the groundwater samples analyzed. However, most of them were found in concentrations below 0.1 µg/L, with imidacloprid, hexaflumuron and oxadixyl being the most frequently detected in 7, 6 and 5 samples, respectively. Only in 5 samples, methiocarb (three samples), pyrethrin I and pytethrin II (one sample) and hezaflumuron (one sample) were found at levels higher than 0.1 μg/L. The method green profile was evaluated using National Environmental Methods Index and analytical Eco-scale assessment tools.

On-site sample pretreatment: Natural deep eutectic solvent-based multiple air-assisted liquid–liquid microextraction

Chemical protection is one of the most important methods to control forest pests. Since pesticides used in chemical protection might have significant adverse effects on aquatic organisms, it is essential to monitor and detect trace pesticides in environmental water. In this study, an on-site natural deep eutectic solvent-based multiple air-assisted liquid–liquid microextraction coupled with gas chromatography-electron capture detection was developed for determining triadimefon, bifenthrin, bromopropylate, and permethrin in water samples in the forest. A series of menthol-based deep eutectic solvents were synthesized for the first time to find green and efficient extractants. Moreover, a deep eutectic solvent with a 1:2 molar ratio of DL-menthol to citric acid was selected as the extractant due to its high stability and extraction performance. A portable modular array device based on air-assisted liquid–liquid microextraction was designed and manufactured to enable the simultaneous pretreatment of several samples. Although no electric equipment is required throughout the process, up to six samples were pretreated on-site within 20 min. Moreover, the average sample pretreatment time was less than 3.5 min, and the process was substantially simplified and enhanced. In addition, the parameters affecting the extraction performance were optimized. The extraction recoveries were in the range of 92–95% by using the optimized conditions, and the relative standard deviations of the intra-device, inter-device, intra-day, and inter-day factors were all less than 4.9%. The detection limits of the method ranged from 0.34 to 3.3 µg L−1. Good linearities (R2>0.999) were shown in the linear range of 1.13 to 2500 µg L−1 for the studied pesticides. Moreover, the proposed method was proved to be highly environmentally friendly by the Analytical Eco-Scale and Green Analytical Procedure Index. In summary, the proposed method is green, efficient, and flexible for on-site water sample pretreatment. The fact that tedious operations can be converted into standard operations provides a new perspective for on-site sample processing.

Covalent organic framework-based magnetic solid phase extraction coupled with micellar electrokinetic chromatography for the analysis of trace organophosphorus pesticides in environmental water and atmospheric particulates

A magnetic covalent organic framework material (M-COF) with conjugated structure, high surface area and good chemical stability, was prepared for the adsorption of nine organophosphorus pesticides (OPPs). The extraction recovery of the M-COF for nine target OPPs were 64–91%, and the extraction dynamics was relatively fast. Based on it, a method by combining magnetic solid phase extraction (MSPE) with sweeping micellar electrokinetic chromatography (MEKC) was developed for the determination of nine OPPs in environmental water and atmospheric particle samples. The enrichment factor (EF) of MSPE-sweeping-MEKC for nine target OPPs are 1740 and 3626 times, with the limits of detection of 0.78–2.33 μg L−1. This method was used to analyze nine OPPs in environmental samples, and the recovery of nine OPPs in spiked East Lake water, Triangle Lake water, the extracts of PM2.5, PM10 and TSP were 81.0–111%, 83.6–111%, 83.1–117%, 81.7–114% and 80.2–114%, respectively. The method is sensitive, rapid and simple, and can be used for the quantification of interest OPPs in environmental samples with complex matrix.

Covalent Organic Framework-Based Magnetic Solid Phase Extraction Coupled with Micellar Electrokinetic Chromatography for the Analysis of Trace Organophosphorus Pesticides in Environmental Water and Atmospheric Particulates

Covalent Organic Framework-Based Magnetic Solid Phase Extraction Coupled with Micellar Electrokinetic Chromatography for the Analysis of Trace Organophosphorus Pesticides in Environmental Water and Atmospheric Particulates

Method development, validation, monitoring, seasonal effect and risk assessment of multiclass multi pesticide residues in surface and ground water of new alluvial zone in eastern India.

A liquid-liquid extraction (LLE) method was validated as per SANTE/12682/2019 guidelines for gas chromatography-mass spectrometric (GC-MS) determination of thirty-six multiclass pesticides in environmental waters. Seasonal (summer, monsoon, and winter) effects on the magnitude of pesticide residues in environmental water (river, pond, and tube well) of six different urban areas of Nadia and North 24 Parganas districts (New alluvial zone, Eastern India) was monitored for subsequent risk assessment. Total 288 water samples (96 each of river, pond, and tube-well) irrespective of locations and seasons were monitored for multiclass multi pesticide residues during the experiment. Each sample (750mL) was extracted with ethyl acetate/dichloromethane (8:2) liquid-liquid partitioning and filtration (0.22μm nylon filter paper) and total residue was reconstituted in acetone (1mL) for GC-MS analysis with developed and validated method resulting satisfactory recovery percentages (77.84-118.15%). The maximum no. of organochlorine (OC) and organophosphorus (OP) pesticide residues were dominated in river and pond water irrespective of seasons and monitoring sites. About 74% of river water samples were found to be contaminated with concerned pesticides in variable magnitudes. Monsoon (July to October) season was highly alarming with the highest presence of total pesticide residues in different types of environmental waters. Risk quotient (RQ) [acute and chronic] was also evaluated in pond and river water as sometimes used for drinking purposes. RQ value (5900) of total endosulfan indicates the highest risk of chronic toxicity to river fishes. Seven water samples from tube-wells were also monitored and found to be contaminated with butachlor and chlorpyriphos in non-significant amounts (< 0.1ngmL-1), irrespective of seasons and sites, thus safe for consumption.

Efficient capture of carbamate and triazole pesticides in environmental waters by functional groups-rich monolithic fibers prior to chromatographic quantification

Efficient capture of carbamate and triazole pesticides in environmental waters is challenging because of their low contents, high water-solubility and complex sample matrices. In the present study, according to the chemical features of carbamates and triazoles, a functional groups-rich monolithic adsorbent (FRMA) was fabricated and employed as the extraction phase of multiple fibers solid phase microextraction (MF-SPME) using 4-vinylphenylboronic acid and vinylimidazole as mixed functional monomers. Results well evidenced that multiple forces such as B-N coordination, H-bonding, π-π and hydrophobic interactions co-contributed the efficient enrichment of FRMA/MF-SPME towards studied pesticides (extraction efficiencies ranged from 76.8% to 91.7%). Under the optimized parameters, sensitive and reliable method for measurement of trace carbamate and triazole pesticides in a variety of water samples was developed by the combination of FRMA/MF-SPME with high performance liquid chromatography (HPLC) equipped with diode array detector (DAD). The limits of detection varied from 0.0049 μg/L to 0.015 μg/L, and the RSDs for precision were below 10%. The recoveries for different fortified contents (1.0 μg/L and 100 μg/L) were in the range of 82.0–119%, and the RSDs for repeatability varied from 2.1% to 9.2%. Compared with existing approaches, the established approach presents some attractive merits such as minimal labor required, good sensitivity, high cost-effectiveness and eco-friendliness. Thus, the introduced approach can serve as a promising alternative method for routine monitoring of carbamate and triazole pesticides in environmental waters.

Effervescent tablet-assisted switchable hydrophilicity solvent-based on-site dispersive liquid-liquid microextraction coupled with gas chromatography for the determination of pyrethroid pesticides in environmental waters

A novel effervescent tablet-assisted switchable hydrophilicity solvent-based on-site dispersive liquid-liquid microextraction coupled with gas chromatography detection has been developed to determine five pyrethroid insecticides in environmental water samples. In this method, effervescent tablets contain effervescent precursors and extractants, which play a dual role of dispersion and extraction. After effervescence reaction, the formation of extractant and the extraction of analytes were accomplished simultaneously. Phase separation were carried by filtration using homemade filter column, which of filter is oil-absorbing cotton polypropylene. After phase separation, the extractant phase were obtained by elution. No electric instrument was required in sample pre-treatment step in the developed method. Experimental conditions affecting the extraction efficiencies have been optimized, such as type and amount of extractant, type of effervescent tablets, etc. Under the optimized conditions, the linearity was 5-500μg L-1, with coefficients greater than 0.9990. The limit of detection and the limit of quantitation were in the range of 0.22-1.88μg L-1 and 0.75-6.25μg L-1. The relative standard deviations ranged from 0.8% to 6.1%. The enrichment factors were in the range of 65-108. This method was successfully applied to the on-site processing of tap, reservoir and river water.

Determination of 18 pesticide residues in environmental water by solid phase extraction-ultra performance liquid chromatography-tandem mass spectrometry

A method was developed for the simultaneous determination of 18 pesticide residues in environmental water by solid phase extraction-ultra performance liquid chromatography-tandem mass spectrometry (SPE-UPLC-MS/MS). The samples were purified and enriched by a large-volume SPE apparatus through a Cleanrt®-PEP SPE column at a rate of 2 mL/min. After being concentrated 50-fold, the samples were detected by UPLC-MS/MS and quantified by the external standard method. The target compounds showed good linearity in the range of 0.5-50 μg/L, with linear correlation coefficients (R2) ≥0.995. At spiked levels of 10, 100 and 1000 ng/L, the average recoveries of the 18 pesticides in the three different environmental water samples were 71.3%-105.9%, and the relative standard deviations (RSDs, n=5) were 1.3%-9.9%. LOQs of the 18 pesticides were 10 ng/L. The method was applied to the detection of the water environment around Tai'an City, and no pesticide residues were detected at any of the collection sites. The method has the advantages of good purification effect, high versatility, sensitivity, and accuracy, and operational simplicity. The method is suitable for the determination of the 18 pesticides in environmental water.

A new carbon nanomaterial solid-phase microextraction to pre-concentrate and extract pesticides in environmental water

This research describes a solid-phase microextraction device using carbon nanomaterials supported on steel threads. The device was used to pre-concentrate and extract 24 pesticides in water. The carbon nanomaterials were obtained by a chemical vapor deposition (CVD) process, using methane and acetonitrile as carbon source. The different pesticides were separated, detected, and quantified using gas chromatography coupled to mass spectrometry (GC-MS). The system, optimized and validated in the laboratory, presented good results. Linearity was between 0.0007 and 50.00 μg L−1, with determination coefficients greater than 0.9. The detection and quantification limits were in the range of 0.0002–1.1309 μg L−1 and 0.0007–3.7320 μg L−1, respectively. The studied pesticides presented recovery values in the range of 70 ± 8 to 123 ± 18%. Carbon nanomaterials exhibited high thermal and mechanical resistance, as the same fiber could be used for approximately 300 extractions. The device was applied to analyze environmental water samples collected from the São Francisco river basin in Brazil and in the Chinampas in Mexico City.

Quantification of Trace Organophosphorus Pesticides in Environmental Water via Enrichment by Magnetic-Zirconia Nanocomposites and Online Extractive Electrospray Ionization Mass Spectrometry.

A total of 15 representative organophosphorus pesticides (OPPs), a class of water pollutants causing serious global concerns, have been sensitively quantified by internal extractive electrospray ionization mass spectrometry (iEESI-MS) after enrichment with Fe3O4-ZrO2 innovatively synthesized in our lab by a one step coprecipitation method. For the premium enrichment, the amounts of Fe3O4-ZrO2, pH value, adsorption time, type and volume of desorption solvent, and shaking time of desorption were systematically optimized. Under optimized conditions, the proposed method provided low limits of detection (LODs) of 0.14-16.39 ng L-1 with relative standard deviations (RSDs) of less than 8.7%. A wide linear response range of about 4 orders of magnitude was achieved with linear coefficients (R2) of 0.9921-0.9999 for all the analytes tested. The present method also provided good recoveries (85.4-105.9%) with acceptable precision (RSDs < 7.2%) in spiked environmental water samples. Furthermore, multiple analytes including dimethoate, omethoate, etc. were simultaneously detected in a single sample run, which was accomplished within 1 min, resulting in significantly improved analytical throughput for quantitative analysis of bulk amounts of samples. The experimental results demonstrated that Fe3O4-ZrO2-iEESI-MS provided advantages, including high sensitivity, high speed, and reasonable selectivity for the detection of OPPs, showing potential applications in environmental water sample analysis and environmental science.

Fabrication of boron-rich multiple monolithic fibers for the solid-phase microextraction of carbamate pesticide residues in complex samples.

To enrich carbamate pesticides from complex matrices, an adsorbent based on poly (vinylboronic anhydride pyridine complex-co-ethylenedimethacrylate) monolith was fabricated and utilized as the extraction phase of multiple monolithic fiber solid-phase microextraction. Due to the abundant boron atoms in the monolith, the B-N coordination interaction between adsorbent and analytes play a key role in the efficient extraction of analytes. Under the optimized conditions, the monolithic fibers were combined with high-performance liquid chromatography for the quantify trace levels of carbamate pesticides in environmental water and orange juice samples. For water sample, the limit of detection and limit of quantification were in the range of 0.017-0.29 and 0.057-0.96μg/L, respectively. The related values in orange juice samples were 0.038-0.39 and 0.12-1.36μg/kg, respectively. Besides, the proposed method also exhibits wide linearity, satisfactory coefficients of determination, and good precision. The introduced approach was successfully applied to determine trace target analytes in real-life samples. The spiked recoveries with different fortified concentrations were in the range of 80.4-117% for water samples and 83.7-119% for fruit juice samples. The relative standard deviations were below 10%. The results evidence that the suggested method was convenient, reliable, and eco-friendly for the monitoring of trace levels of carbamate pesticides in complex samples such as waters and juices.

Magnetic core micelles as a nanosorbent for the efficient removal and recovery of three organophosphorus pesticides from fruit juice and environmental water samples.

Sodium dodecyl sulfate coated amino-functionalized magnetic iron oxide nanoparticles were used as an efficient adsorbent for rapid removal and preconcentration of three important organophosphorus pesticides, chlorpyrifos, diazinon and phosalone, by ultrasound-assisted dispersive magnetic solid-phase microextraction. Fabrication of amino-functionalized magnetic nanoparticles was certified by characteristic analyses, including Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and transmission electron microscopy. Affecting parameters on the removal efficiency were investigated and optimized through half-fractional factorial design and Doehlert design, respectively. The analysis of analytes was performed by high-performance liquid chromatography with ultraviolet detection. Under the optimum conditions, extraction recoveries for 20ng/mL of organophosphorus pesticides were in the range of 84-97% with preconcentration factors in the range of 134-155. Replicating the experiment in above condition for five times gave the relative standard deviations <6%. The calibration curves showed high linearity in the range of 0.2-700ng/mL and the limits of detection were in the range of 0.08-0.13ng/mL. The proposed method was successfully applied for both removal and trace determination of these three organophosphorus pesticides in environmental water and fruit juice samples.

Application of a magnetic graphene nanocomposite for organophosphorus pesticide extraction in environmental water samples

A novel magnetic nanocomposite was prepared and applied for the extraction of organophosphorus pesticide residue (malathion, chlorpyrifos, isocarbophos, fenamiphos, profenofos) in environmental water by magnetic solid phase extraction. The magnetic nanocomposite was synthesized by coating Fe3O4 with silicon dioxide and then bonding with graphene oxide under the catalytic action of hydrazine hydrate. A residue analysis method for the determination of organophosphorus pesticides in environmental water was established via magnetic solid phase extraction with the nanocomposite as the sorbent, followed by gas chromatography with flame photometric detection (GC-FPD). Various experimental parameters affect extraction efficiency and must be optimized, such as the sorbent amount, the type and volume of desorption solvent, desorption time, desorption step, salt concentration and pH. Under the optimum conditions, a linear response was achieved for malathion and chlorpyrifos in the concentration range of 0.05 mg L−1–5 mg L−1. Other organophosphorus pesticides were quantified in a concentration range of 0.1 mg L−1–5 mg L−1, and the coefficient of correlations were between 0.996 and 1 for this method. The method was used to determine organophosphorus pesticides in river water and groundwater. The average recoveries ranged from 90.2% to 102.9%, with low relative standard deviations (RSD), and the limits of detection (LOD) were between 0.016 mg L−1 to 0.033 mg L−1 at a signal to noise ratio of 3. The method was efficient for the residue analysis of organophosphorus pesticides in water with easy operation, high sensitivity, and good precision.

MCM-41 as novel solid phase sorbent for the pre-concentration of pesticides in environmental waters and determination by microflow liquid chromatography-quadrupole linear ion trap mass spectrometry

The present work describes a novel solid phase extraction method based on the MCM-41 sorbent for the pre-concentration of eight pesticides with different polarity (including organophosphates, carbamates and triazoles) in environmental waters. A microflow liquid chromatography-quadrupole linear ion trap mass spectrometer was used for the determination and extra-confirmation of the pesticides in the water. Variables affecting the retention (pH and ionic strength) and elution (type and volume elution solvent) of the analytes, the sorbent amount and the breakthrough volume were optimized. The effect of the matrix components in the response of the pesticides was investigated in two types of environmental water (river and dam waters). Signal suppression, which was found in all cases depends on the analyte and the kind of the sample; therefore, quantification was carried out using the standard addition approach. Detection and quantification limits achieved in environmental samples were lower than 0.01μgL−1 and 0.05μgL−1, respectively (with the exception of cymoxanil in dam water, which showed a quantitation limit of 0.16μgL−1). Accuracy and precision in environmental samples, at two concentration levels, ranged from 65% to 126% (relative standard deviation≤14%), except for methomyl with recoveries lower than 60%. The method developed herein was applied to the analysis of several environmental waters from Spain in which pesticides were not found in any case. Diffusion NMR methods and 13C CP/MAS NMR were applied in order to establish that MCM-41 selectively interacts in different extent with pesticides of different polarity such as cymoxanil or phosalone.

Versatile magnetic carbon nanotubes for sampling and pre concentration of pesticides in environmental water

This article describes a simple, efficient, and versatile magnetic carbon nanotubes (MCNT) method for sampling and pre-concentration of pesticides in environmental water samples. The multi-walled magnetic carbon nanotubes were obtained by chemical deposition vapor (CVD) process. The MCNTs structures are formed of hydrophobic and hydrophilic fractions that provide great dispersion at any water matrix allowing simultaneously a high efficiency of pesticides sorption. Following the extraction, analytes were desorbed with minor amounts of solvent and analyzed by gas chromatography coupled mass spectrometry (GC/MS). The parameters amount of MCNTs used to extraction, desorption time, and desorption temperature were optimized. The method showed good linearity with determination coefficients between 0.9040 and 0.9733. The limits of detection and quantification were ranged between 0.51 and 2.29µgL−1 and between 1.19 and 5.35µgL−1 respectively. The recovery ranged from 79.9% to 111.6%. The method was applied to the determination of fifteen multiclass pesticides in real samples of environmental water collected in Minas Gerais, Brazil.