Insecticides In Water Research Articles

Neonicotinoid insecticides in waters of Hongze lake, the largest impounded lake on the South-to-North water diversion project, China: Implications for environmental and public health

Contamination by neonicotinoid (NEO) insecticides in surface waters is a global problem. Nevertheless, the occurrence of NEOs in lakes is not well known. Hongze Lake, the largest impounded lake on the Eastern Route of the South-to-North Water Diversion Project, was selected to investigate the distribution, ecological risks, and health risks of NEOs. Water samples from the lake and nearby rivers were collected and analyzed for 8 widely used NEOs in three seasons. The results indicated the average total NEO concentration in summer, winter, and spring was 222, 211, and 244 ng L−1 for the river water, and 265, 213, and 181 ng L−1 for the lake water, respectively, with no statistical seasonal difference. For the river water, the highest total NEO concentration in the three seasons was observed in the Andong River. For the lake water, the total NEO concentrations in summer were relatively high in sites near the inflow river estuaries due to the high riverine inputs during the flood period. The spatial difference in NEO concentration was relatively low in winter, which may be related to the wind-driven lake current. The seasonal variation in NEO compositions in the lake was generally similar to that in the river, indicating riverine input was the important source for the lake. Huai River was the largest contributor to the NEO inputs to the lake, and Sanhe Gate was the major output pathway. Clothianidin and imidacloprid in the river and lake water would produce moderate acute ecological risks in summer. Thus, the usage of the above two NEOs should be decreased or restricted. For integral NEO risks, 53% and 58% of the river and lake water sites exceeded the acute ecological threshold, respectively. Health risk assessment suggested drinking the water obtained from the lake would not produce a negative impact on public health.

Rhamnolipids-based bio-supramolecular solvents as green and sustainable media for extraction of pyrethroid insecticides in water and food matrices

A novel bio-supramolecular solvent (bio-SUPRAS) based on rhamnolipids (RLs) was designed for efficient extraction of pyrethroid insecticides in water and food matrices. Benefiting from RLs as amphiphiles equipped with the attractive properties of bio-degradable, low toxicity and high stability, bio-SUPRAS was spontaneously generated through salt induced coagulation. The bio-SUPRAS was characterized by cryo-scanning electron microscope and main factors influencing the extraction performance were investigated in detail. Under the optimized conditions, the method was found to have desirable limits of detection (5∼10 μg l-1), good precision (RSDs<16.9 %) and satisfactory recovery (75.2 %∼94.3 %). More importantly, the extraction mechanism was studied by density functional theory systematically. Following greenness assessment, the technique was successfully used for enrichment of pyrethroid pesticides in real samples before HPLC-UV analysis. Thus, the method showed the outstanding merits of eco-efficient, green, time-saving, and had favorable application prospect to remove trace analytes from intricate sample matrices.

Neonicotinoid insecticides in waters of the northern Jiangsu segment of the Beijing-Hangzhou Grand Canal: Environmental and health implications

Neonicotinoid (NEO) insecticides have been frequently detected in natural aquatic environments. Nevertheless, the distribution of NEOs in artificial environments is not clear. The Beijing-Hangzhou Grand Canal is the longest canal in the world. The northern Jiangsu segment of the Grand Canal was selected to study the spatiotemporal variation and source of eight NEOs in the canal water and assess their ecological and health risks. The total NEO concentration in the canal water was 12–289 ng L−1 in the dry season and 18–373 ng L−1 in the wet season, which were within the concentration range in other 11 natural rivers worldwide. The average total NEO concentrations were not statistically different between the seasons; only the concentrations of imidaclothiz, thiacloprid (THI), acetamiprid, and dinotefuran were different. At city scale, the total NEO concentration in the dry season showed a decreasing trend along the water flow from Xuzhou City to Yangzhou City. The total NEO concentrations were found to be positively correlated with the sown area of farm crops and the rural labour force, indicating the agricultural influence on the spatial distribution of NEO concentrations. In the wet season, relatively high NEO concentrations were distributed in downstream sites under the influence of artificial regulation. The primary contributor to the NEO inputs into the canal was the nonpoint source in the dry and wet seasons, with a relative contribution of 68 %. THI, imidacloprid, clothianidin and thiamethoxan would produce chronic ecological risks in both seasons. Further consideration needs to be given to the above four NEOs and NEO mixtures. The human health risks that NEOs posed by drinking water were assessed based on the chronic daily intake (CDI). The maximum CDI for adults and children was lower than the reference doses. This suggested public health would not be at risk from canal water consumption.

Spatial distribution and risk assessment of pyrethroid insecticides in surface waters of East China Sea estuaries

Pyrethroid insecticides are the most commonly used household insecticides and pose substantial risks to marine aquatic organisms. many studies have detected pyrethroid insecticides in the waters and estuaries of the western United States, but their distributions within western Pacific estuaries have not been reported. Accordingly, we used high-throughput organic analyses combined with high volume solid-phase extraction to comprehensively assess 13 pyrethroid insecticides in East China Sea estuaries and the Huangpu River. The results demonstrated the presence of various ∑13pyrethroid insecticides in East China Sea estuaries (mean and median values of 8.45 ± 5.57 and 7.78 ng L−1, respectively), among which cypermethrin was the primary contaminant. The concentrations of ∑12pyrethroid insecticide detected in the surface waters at the Huangpu River (mean 6.7 ng L−1, outlet 16.4 ng L−1) were higher than those in the Shanghai estuary (4.7 ng L−1), suggesting that runoff from inland areas is a notable source of insecticides. Wetlands reduced the amount of runoff containing pyrethroid insecticides that reached the ocean. Several factors influenced pesticide distributions in East China Sea estuaries, and higher proportions were derived from agricultural sources than from urban sources, with a higher proportion of agricultural sources than urban sources, influenced by anthropogenic use in the region. Permethrin and cypermethrin were the main compounds contributing to the high ecological risk in the estuaries. Consequently, to prevent risks to marine aquatic life, policymakers should aim to reduce insecticide contaminants derived from urban and agricultural sources.

Sea-urchin-like covalent organic framework as solid-phase microextraction fiber coating for sensitive detection of trace pyrethroid insecticides in water

Pyrethroid insecticides residues in water pose a critical threat to the environment from widespread production and overuse. Therefore, it is of major relevance to develop a sensitive and efficient method to detect pyrethroid insecticides in water. In this paper, a covalent organic framework (COF) with NHCO as the structural unit was synthesized using a simple condensation reaction of TTL (NH2) and TDBA (COOH). Various characterization results and density functional theory (DFT) calculations demonstrated that multiple interactions synergistically promoted the adsorption of pyrethroid insecticides on COFTDBA-TTL. Based on the excellent extraction capability of COFTDBA-TTL, efficient detection of 11 pyrethroid insecticides in water was achieved using COFTDBA-TTL-coated SPME fiber and gas chromatography-tandem mass spectrometry (GC–MS). The results showed that the extraction enhancement factors (EFs) of pyrethroid insecticides were as high as 2584–7199, and the extraction efficiencies were 3.28–446 times higher than that of commercial fiber, which reflected its high adsorption property. Meanwhile, the limits of detection (LODs) of the COFTDBA-TTL coated fiber were as low as 0.170–1.68 ng/L under the optimal conditions, and the recoveries of 11 pyrethroid insecticides in the actual water samples were 88.5–108 %. In conclusion, the SPME-GC–MS method based on COFTDBA-TTL coated fiber was simple, rapid, and efficient, and should have a promising application in trace detection of pyrethroid insecticides in the environment.

Synthesis of phosphate-functionalized magnetic porous organic polymer: A sorbent for sensitive determination of neonicotinoid insecticides in water and lemon juice

There is an urgent need to prepare advanced functional materials for extraction and enrichment of trace organic pollutants from different samples. In this work, two novel phosphate-functionalized porous organic polymers (DBP-POP and DPP-POP) were synthesized for the first time. Compared with phosphate-free counterpart, both phosphate-functionalized POPs showed excellent adsorption performance for the neonicotinoids due to the hydrogen bonding, π-π interaction and hydrophobic interaction. For ease of separating the sorbent from solution, magnetic DBP-POP (M-DBP-POP) was further prepared as sorbent to extract neonicotinoids from environmental water and lemon juice samples prior to their determination by high performance liquid chromatography-ultraviolet detection. Under optimal conditions, the detection limits (S/N = 3) of the method were 0.01–0.08 ng mL−1 for water and 0.03–0.10 ng mL−1 for lemon juice. The recoveries were in the range of 80.0% to 113.0% with relative standard deviation less than 10.6%. This work demonstrated the feasibility of phosphate-functionalized POPs for adsorption applications.

The impact of two insecticides on the pollutant cycle and quality of surface and groundwater resources in the irrigated lands of Yasuj, Iran

The increase in the need for food and agricultural development has led to an increase in the use of insecticides. The use of insecticides leads to air, soil and water pollution. This study investigated the pollutant concentration cycle in the environment by analyzing diazinon and deltamethrin in a river and groundwater sources affected by an agricultural area. The samples were analyzed based on the standard method for insecticides in water using a GC-MS. The results showed that the quality of the surface water affected by the agricultural effluents decreased so that the changes of dissolved oxygen, nitrate, turbidity, TOC, BOD, and COD were 15.2%, 189.6%, 00%, 53%, 176%, and 57.5%, respectively. The concentration of diazinon and deltamethrin in agricultural wastewater was 86 μg/L and 11.62 μg/L. The self-treatment capacity of the river reduced the concentration of diazinon in the distance of 2 km and 15 km by 80.8% and 90.3%, respectively. These conditions were observed for deltamethrin in 74.8% and 96.2%, respectively. Also, the concentration of the two insecticides in water resources has temporal and spatial variation. The difference between the maximum and minimum concentration of diazinon and deltamethrin at different times was 183.5 and 1.73, respectively. The concentration of diazinon and deltamethrin in the downstream groundwater of the studied irrigated area was 0.3–0.7 μg/L, respectively. Although the soil structure and the self-purification capacity of the river caused a significant reduction of insecticides, the remained concentration of these pollutants in underground and surface water resources can still be a health and environmental concern.

Monitoring and environmental risk assessment of agricultural fungicide and insecticides in water, sediment from Kumkale Plain, Çanakkale-Turkey

This study was conducted to assess pesticide residues in 34 water and sediment samples taken from Kumkale Plain of Çanakkale-Turkey. Residue analyses were performed with the use of Quick-Easy-Cheap-Efficient-Rugged-Safe (QuEChERS)-liquid chromatography/tandem mass spectrometry (LC-MS/MS) procedure. For method verification, blank sediment and water samples were spiked at two limits of quantification (LOQ) levels of the pesticides. Overall recovery was 81.66% for sediment and 91.50% for water samples. In sediment samples, chlorpyrifos-M had the highest concentration, pyridaben was encountered in the majority of the samples (15 samples) and the highest number of pesticides (35) was seen in sample no. s13. In water samples, methoxyfenozide had the greatest concentration, metalaxyl was encountered in the highest number of samples (three samples) and the highest number of pesticide (8) was seen in sample no.w13. Sample no. s13 and w13 were taken from around the fountain basin. Pyraclostrobin and chlorantraniliprole residues exceeded the national limits set for water. In terms of hazard quotient (HQ), pesticides in sediment and waters were found to be safe. Despite the safe nature of pesticide on samples, greater attention has been paid on toxicity of the residues. It was concluded that authorities should put strict regulations on agrochemicals to reduce health risks of these chemicals.

Persistence, sorption, and forced degradation of imidacloprid in environmental matrix

The enhanced utilization of insecticides over various crops has led the toxicity in the environmental matrix. In this study, the behavior of Imidacloprid is observed in soil and water. The adsorption–desorption characteristics of Imidacloprid are observed on three different soils (Bathinda, Moga, and Sangrur) of the Malwa Region. The soil of Bathinda has shown maximum adsorption followed by Sangrur and then by Moga soil. The reverse order is observed in the desorption process under optimum conditions of pH 6 and temperature 33 °C. The adsorption behavior is observed to be related to the mineral content of the soils. The various adsorption and kinetic models reveal the suitability of chemical adsorption. The persistence study indicates the presence of insecticide in water for more than 100 days. In the forced degradation studies, ZnO photocatalyst has shown higher degradation of Imidacloprid nearly 91 % after 5 h under UV light, whereas with TiO2, degradation has reached up to 85 % during the same period.

Direct solidification of switchable-hydrophilicity salicylic acid: A design for the on-site dispersive liquid-liquid microextraction of benzoylurea insecticides in water and honey samples

This study describes the development of a fully manual method for on-site dispersive liquid-liquid microextraction based on the direct solidification of switchable-hydrophilicity salicylic acid (on-site DLLME-DSSA) coupled with high-performance liquid chromatography with an ultraviolet detector (HPLC-UVD) and its utilization for the detection of benzoylurea insecticides (BUs) in water and honey samples. Salicylic acid (SA), a switchable hydrophilic aromatic acid, was used as an extraction solvent. It can be converted into the hydrophobic/hydrophilic forms in pH-changeable solutions, facilitating facile and effective dispersion and phase separation. Moreover, the melting point of SA (significantly higher than room temperature) enables its direct solidification without an ice-water bath, facilitating its collection by filtration. The dispersion, separation, and collection of the extraction solvent were carried out entirely in a plastic syringe without requiring special apparatus or additional energy. Univariate and response surface analyses were used to optimize various parameters of the on-site DLLME-DSSA method. Under optimal conditions, the limits of determination (LODs) were 1.50 µg L−1 and 0.03–0.09 mg kg−1 in water and honey, respectively. The relative standard deviations (RSDs) for inter-day (n = 5) and intra-day (n = 5) precision were ≤8.4%, whereas the extraction recoveries and enrichment factors for the BUs ranged from 67.0 to 97.1% and 29 to 34, respectively. Furthermore, the proposed method was used for the on-site extraction and laboratory detection of BUs from real water and honey samples. Theoretical analyses indicated non-covalent interactions (such as hydrogen bonds, electrostatic interactions, van der Waals forces, and π-π interactions) to be the main driving force for extraction. This study introduces a switchable hydrophilic aromatic acid capable of direct solidification into on-site DLLME for the first time, opening new frontiers in the development of on-site sample pretreatment methods.

Magnetic Nanocomposite-Based TpPa-NO2 Covalent Organic Framework for the Extraction of Pyrethroid Insecticides in Water, Vegetable, and Fruit Samples

Magnetic Nanocomposite-Based TpPa-NO2 Covalent Organic Framework for the Extraction of Pyrethroid Insecticides in Water, Vegetable, and Fruit Samples

A review of spatiotemporal patterns of neonicotinoid insecticides in water, sediment, and soil across China.

Neonicotinoid insecticides (NNIs) have been widely used to control insect pests, while their environmental residues and associated hazardous impacts on human and ecosystem health have attracted increasing attention worldwide. In this study, we examined the current levels and associated spatial and temporal patterns of NNIs in multiple environmental media across China. Concentrations of NNIs in surface water, sediment, and soil were in the range of 9.94-755ng·L-1, 0.07-8.30ng·g-1 DW, and 0.009-356ng·g-1 DW, respectively. The high levels of NNIs in surface water, such as in Yangtze River (755ng·L-1), North River (539ng·L-1), Nandu River (519ng·L-1), and Minjiang River (514ng·L-1), were dominated by imidacloprid, thiamethoxam, and acetamiprid due to their extensive use. The levels of NNIs in sediments were relatively low, and the highest concentration (8.30ng·g-1 DW) was observed in Dongguan ditch. Sediment-water exchange calculated from fugacity fraction indicated that NNIs in sediment can be released back into the water due to their high solubility and low KOW. Soils from agricultural zones contained the largest residual NNIs, with imidacloprid concentrations in cultivated soil reaching 119ng·g-1 DW. The calculated leaching potential showed that clothianidin has the highest migration potential to deep soil or groundwater. The monitored data of NNIs presented a decreasing trend from 2016 to 2018, which might be caused by the implementation of relevant control policies for NNI applications. The high levels of NNIs mainly occurred in southern China due to frequent agricultural activities and warm and humid meteorological conditions. The results from this study improve our understanding of the pollution levels and environmental behavior of NNIs in different environmental media across China and provide new knowledge that is needed for making future control policies for NNIs production and application.

CuMgFe-LDO as superior peroxymonosulfate activator for imidacloprid removal: Performance, mechanism and effect of pH

Recently, the pollution of neonicotinoid insecticides in aquatic environment has attracted attention. Due to its potential neurotoxicity, it is necessary to develop convenient and high-efficient methods to degrade neonicotinoid insecticides in water. In this study, a heterogeneous composite catalyst CuMgFe-LDO was prepared by precipitation-calcination method, and then used to activate peroxymonosulfate (PMS) to degrade a common neonicotinoid insecticide imidacloprid. The key parameters such as Cu:Mg:Fe ratio, catalyst dosage, PMS dosage and initial pH value were optimized. The results showed that CuMgFe-LDO/PMS system exhibited excellent catalytic performance, and imidacloprid could be completely degraded within 15 min under the optimum conditions ([CuMgFe-LDO] = 50 mg L−1, [PMS] = 0.2 mM and [imidacloprid]0 = 10 μM, initial pH = 4–9). Through quenching experiment, EPR test and characterization analysis, it was identified that the main active species in the system were Cu(III), SO4– and OH. In addition, pH had a great impact on the contribution of these active species. During the reaction, Cu and Fe may participated in valence circulation, and Mg was beneficial to the hydroxylation of catalyst surface and stabilization of copper ions. Finally, the main degradation pathways of imidacloprid were obtained by UPLC-MS/MS analysis, and the toxicity of the intermediate products was calculated with TEST program. In this paper, a high-efficient PMS activation strategy is proposed, which provided a reference for the further development of metal catalysts for advanced oxidation technology.

Ionogel sorbent coatings for determining organophosphorus and pyrethroid insecticides in water and fresh juice samples by headspace-solid phase microextraction

The sol–gel method yielded three different ionogel sorbent coatings that were obtained based on a silica material containing ionic liquids (ILs) immobilized in its pores. Two ILs, triethylsulfonium bis(trifluoromethylsulfonyl)imide [Set3][TFSI] and 1-butyl-1-methylpiperidinium bis(trifluoromethylsulfonyl)imide [C4C1Pip][TFSI], as well as their equimolar mixture [Set3/C4C1Pip], were used to obtain ionogel fibers. The developed sorbents were applied to extract six different insecticides from liquid samples. The crucial extraction parameters of headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography with flame ionization detection (GC-FID) method were optimized with a central composite design. The ionogel fibers demonstrated higher selectivity for extracting the analyzed insecticides compared with commercially available fibers. The calculated values of the enrichment factor were in the ranges of 41,400–106,100 for [Set3], 110,600–170,500 for [C4C1Pip], and 76,800–121,100 for [Set3/C4C1Pip]. The [Set3/C4C1Pip] ionogel fiber, demonstrated the highest selectivity for extraction the insecticides. Regarding this coating, the limit of detection in the range of 0.02–0.95 μg L−1, coefficient of determination, which were <0.9690, and a 2.1 %–6.5 % repeatability of the method were achieved. Finally, the obtained ionogel fibers were utilized to determine insecticides in fresh apple and carrot juices.

Forecasting of Dangerous Influence of Avermectin Insecticides to Human Organism Using Surface and Groundwater for Drinking

More than 400 types of harmful organisms cause damage to agricultural crops. Insecticides occupy one of the last places in the structure of the pesticides assortment among formulations authorized for application in the world. However, they occupy the first place according to their toxicity and the hazard effect to the human body. The purpose of our study was comparative hygienic assessment of soil stability, surface and groundwater migration potential, prediction of dangerous effects of insecticides-avermectins on the human body after using surface and groundwater for drinking needs. For an integral assessment of the potential danger of pesticide exposure to the human body after consumption of water from surface and groundwater supply sources, a scale of four gradations was used. It includes the LEACH (index of potential contamination of groundwater and river waters), half-life period (DT50) in water and an allowable daily dose (ADD) or acceptable daily intake (ADI). It has been established that in different soil and climatic conditions, according to the LEACH index, there is a very low risk of groundwater and surface water contamination. This is due to their relatively high solubility in water, low soil persistence and very high values of the organic carbon sorption coefficient. According to the IIWH index (integral index of water hazard), abamectin and emamectin benzoate in different soil and climatic conditions are moderately hazardous for a person after consumption of contaminated drinking water (class 3); emamectin benzoate in the soil and climatic conditions of Ukraine is hazardous (class 2). It is necessary to monitor carefully the boundaries of sanitary-protective areas from treated areas to water bodies, and control the process of exploitation of water supply sources, especially decentralized in rural areas. In regions with intensive agricultural production, it is recommended to use the IIWH index to make a decision about the necessity of monitoring research on insecticides in water.

One step extraction followed by HPLC-ESI-MS/MS for multi-residue analysis of diacylhydrazine insecticides in water, sediment, and aquatic products

A multi-residue analysis of six diacylhydrazine insecticides in water, sediment, and aquatic products was established by liquid chromatography triple quadrupole tandem mass spectrometry (LC-MS/MS). The water sample was extracted with acetonitrile by low-temperature enrichment liquid-liquid extraction technology. The sediment and aquatic products were prepared using QuEChERS technique. Method validation showed perfect linearity with correlation coefficients (R) more than 0.9992 for all insecticides, and the matrix effects were nearly negligible (−1.42% to −0.27%) for water, sediment and aquatic products. The recoveries were 80.0–99.7% at three spiked levels (0.02 ng·mL−1, 0.1 ng·mL−1, 0.5 ng·mL−1; 2.0, 10, and 50 ng·g−1) and the precisions (intra-day and inter-day precision) were lower than 5.28%, with the low LODs (3.8 ~ 9.6 pg·mL−1; 0.38–0.96 ng·g−1) and LOQs (12.7 ~ 32.0 pg·mL−1; 1.27–3.20 ng·g−1) for water, sediment, and aquatic products, indicating the good accuracy and precision of the proposed method. The applicability, efficiency, and sensitivity of this method have been proved in the analysis of six diacylhydrazine insecticides in water, sediment, and crucian carp in Rice- crucian carp - integrated planting system.

Effects of pesticides on Chelon labrosus (Risso, 1827) evaluated by enzymatic activities along the north eastern Sicilian coastlines (Italy)

Pesticides are frequently applied to agricultural activities to improve harvest, in terms of yield and product quality. Useful tools for ecotoxicological studies of marine ecosystems are based on biomarker application on bioindicator key fish species. The main aim of the present study was to detect the potential presence of pesticides in a polluted coastal marine environment, namely Milazzo Gulf, situated in the north eastern coast of Sicily (Italy), by measuring the enzymatic activities of the ecotoxicological biomarkers acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) in brain and blood samples of Chelon labrosus. Also, Marinello Reserve was selected as a reference site. The data showed a significant inhibition in AChE (81%) and BChE (71%) activities in fish from Milazzo Gulf in respect to those from the reference site. The esterase inhibition is primarily due to the presence of organophosphorus insecticides and carbamates that resulted, in Milazzo Gulf, higher in concentration in respect to the reference quality standard decree (D.M. 260, 2010). The results obtained in this study confirm the suspected presence of insecticides in waters and fish from Milazzo Gulf, which may lead to a considerable hazard to humans. This study confirms the relevant advantages of the biomarker approach on fish species in the ecotoxicological evaluation of marine environments.

Metal-organic framework MIL101 (Cr)-NH2 functionalized magnetic graphene oxide for ultrasonic-assisted magnetic solid phase extraction of neonicotinoid insecticides from fruit and water samples

In this work, a magnetic nanocomposite composed of graphene oxide (GO), silica-coated cobalt ferrite (CoFe2O4@SiO2) nanoparticles and amino-functionalized metal-organic framework (MIL 101 (Cr)-NH2) was fabricated and employed for ultrasonic-assisted magnetic solid phase extraction (UA-MSPE) of neonicotinoid insecticides. Various techniques such as Fourier transform infrared (FT-IR) spectrometry, vibrating sample magnetometry (VSM), energy-dispersive X-ray spectroscopy (EDS) and field emission scanning electron microscope (FE-SEM) measurements were executed to investigate features and morphology of the adsorbent. The magnetic graphene oxide functionalized MIL-101 (Cr)-NH2 (MGO/MIL) combines the advantages of magnetic GO and MIL 101(Cr)-NH2 such as excellent thermal and chemical stability, high surface area, accessible coordinative unsaturated sites, sufficient stability in aqueous solutions and rapid and easy separation from the solution. Some of the important extraction factors such as type and volume of desorption solvent, desorption time, salt concentration, adsorbent amount, pH and extraction time were investigated in detail to achieve high MSPE recovery. In optimal condition, the limits of detection (LODs) for Acetamiprid and Imidacloprid were achieved 0.022 and 0.019 ng mL−1, respectively. Good determination coefficients (R2 more than 0.9990) with satisfactory linearity in the range of 0.064–3500 ng mL−1 were found for this method. The relative standard deviations for intra- and inter-day analyses were in the range of 3.93–4.56% and 7.80–8.50%, respectively. The method was successfully used for analyzing of neonicotinoid insecticides in water and fruit samples and acceptable recoveries from 82.13% to 102.27% were obtained. The results indicated that the nanocomposite is feasible for the adsorption of trace amounts of the target analytes from the fruit and water samples.

Preparation and Characterization of Metal Oxide Sensors and Their Application for the Detection of Organophosphate Insecticides

This study focuses on the synthesis and characterization of metal oxides doped with transition metals with the purpose of enhancing their sensitivity to detect organophosphate insecticides, Chlorpyrifos and Malathion, on air. The moderate toxicity of these organophosphorus pesticides and their extensive use in small-scale agriculture reveals the urgency of continuous air quality monitoring in the work environments of communities with restricted access to sophisticated techniques for detecting these contaminants, such as high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS).The selected metal oxides are Zr doped zinc oxide (ZnO) and tin oxide (SnO2) doped with both Pt and Zr. These semiconductors (ZnO and SnO2) have the advantage of showing a sensing response at low working temperatures, in the range of 200°C and 250°C. Additionally, both have great thermal and chemical stability. The synthesis of ZnO is performed through the application of a hydrothermal synthesis methodology in an autoclave; while ZnO doping is conducted by adding the dopant precursor (ZrOCl2) to the reaction mixture. In the case of SnO2, commercial tin oxide is used for doping with Zr and Pt. The doping process was carried out in two separate processes: 1) mechanical mixing and sintering of ZrO2 and SnO2, and 2) chemical reduction of H2Cl6Pt with SnSO4 on the surface of SnO2. The characterization of these materials is carried out by employing X-ray diffraction (DRX), Fourier-transformed infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis), scanning electron microscopy / energy dispersive X-ray spectroscopy (SEM/EDS), transmission electron microscopy (TEM) and sorption of N2 analysis. In addition, the quantification of pesticide concentration in commercial samples, that are used in the sensing essays, is performed with HPLC.The Pt doped SnO2 is prepared with a content of Pt between 0.05 and 0.2 wt. %, while the concentration of Zr is in the range of 0.3 and 0.7 wt. %. In the case of ZnO, the concentration of Zr is between 0.9 and 2.0 wt. %. The characterization by DRX reveals a substitutional doping for both materials. Additionally, the dopants produce an increase of the lattice strain and a small contraction of the unit cell in both metal oxides. The SEM analysis of Zr doped ZnO allows to identify changes in their morphology, which confirms an increase in particle size at Zr concentration of 2.0 wt. % in comparison to 1.2 wt. %.The sensing tests of the doped metal oxides are evaluated in an electronic nose. This equipment allows to test four sensors each time and the vapors of the pesticides are produced through a bubbling process of a liquid suspension of one organophosphate insecticide in water. The prepared doped oxides present an enhanced sensibility for the detection of organophosphates on air. Response signals are obtained with greater stability for long sensing times with zinc oxide sensors doped with Zr at 2.0 wt. % in comparison to sensors of Zr doped ZnO with lower Zr content.A study of the optimum temperature conditions (between 210°C and 220°C) and concentration of the dopant in zinc oxide and tin oxide is carried out. The temperature has a positive effect on the sensitivity of all the sensors tested. At the test temperature of 220°C, the sensitivity of the best sensors (AT-Zr-2.0-ZnO and Pt-0.13-ZrO2-0.15-SnO2) for Malathion can be maximized. In the case of Chlorpyrifos, better results are obtained for the Pt-0.13-ZrO2-0.15-SnO2 sensor, whose signal is favored at 210°C. In addition, the sensitivity of Pt-0.13-ZrO2-0.15-SnO2 with respect to AT-Zr-2.0-ZnO at 220°C is higher for Chlorpyrifos, but lower for Malathion.The statistical treatment method of principal component analysis (PCA) allows the evaluation of the signals of samples with different concentrations of pesticides. The best PCA, obtained with the data of the measurements using the most sensitive sensors, show a total explained variance greater than 90% and a better differentiation between air samples contaminated with pesticides and air samples without contamination. Figure 1

Dissolvable Mg/Al layered double hydroxides and surfactant as an extractant for trace analysis of benzoylurea insecticides by high performance liquid chromatography.

A rapid and simple preconcentration method using dissolvable Mg/Al layered-double hydroxides (LDHs) and high performance liquid chromatography-photodiode array detection (HPLC-PDA) was developed for the analysis of benzoylurea insecticides (BUs) in water and honey samples. The proposed dissolvable LDHs for the extraction can be prepared in one step by the sequential addition of sodium hydroxide, magnesium chloride, aluminium chloride, and sodium dodecyl sulfate into the sample solution containing the target BUs. The co-precipitate phase was simply obtained after centrifugation, and the phase was then dissolved with formic acid before analysis by HPLC. The developed method provided an enrichment factor of 12.5-23.7. LODs were obtained in the range of 0.1-0.3 μg L-1 for deionized water, 0.2-2.0 μg L-1 for environmental waters, and 0.5-2.0 μg L-1 for the analyzed honey samples. Good recoveries ranging from 78.4 to 117.8% and 72.7 to 117.9% for water and honey samples, respectively, were obtained.