Residue levels and risk assessment of acetamiprid-pyridaben mixtures in cabbage under various open field conditions.

Acetamiprid and pyridaben are highly efficient insecticides widely used to protect leafy vegetables against various pests, such as Phyllotreta striolata, but analyses of their residual behaviors applied in mixtures in cabbage fields are primarily lacking. Herein, field trials were performed by spraying 50% acetamiprid-pyridaben wettable powder (50% WP) once at a dose of 150 g of active ingredient per hectare in 12 representative provinces of China under Good Agricultural Practices. The residues of acetamiprid and pyridaben were detected using modified Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) and liquid chromatography-tandem mass spectrometry, together with an assessment of their dietary risks. The average recoveries of the two insecticides were 84.6-104%, and the relative standard deviations were 0.898-10.1%. The residual concentrations of acetamiprid and pyridaben at the preharvest interval of 7 days were <0.364 and 0.972 mg/kg, respectively, and less than their maximum residue limits in cabbage (0.5 mg/kg for acetamiprid and 2 mg/kg for pyridaben) in China. The chronic and acute risk values of acetamiprid and pyridaben were 0.0787-33.3%, implying acceptable health hazards to Chinese consumers. In conclusion, applying 50% WP in cabbage fields under Good Agricultural Practices is acceptable. These results provide essential data for using mixtures of acetamiprid and pyridaben in cabbage fields.

Digestion dynamics of acetamiprid during royal jelly formation and exposure risk assessment to honeybee larva based on processing factor.

Previous studies to the exposure effects of acetamiprid on honeybees were based on the analysis of bee pollen and honey sacs from field trials or of beebread and honey in the hive, which overestimate or underestimate the risk of exposure to pesticide residues. It was believed that the processing factor (PF) is an important variable to determine the final pesticide residue during royal jelly formation and the actual risk to honeybee larva. Hence, a QuEChERS method to determine acetamiprid contents in honeybee samples was established in this study. Then, the PFs for acetamiprid in beebread fermentation, honey brewing, and royal jelly formation were determined to be 0.85, 0.76, and 0.16, respectively. The PF for royal jelly formation was 0.04 when acetamiprid was detected in beebread alone, and it was 0.12 when acetamiprid was only detected in honey. Finally, the predicted exposure concentration of acetamiprid in royal jelly was calculated to be 2.05 µg/kg using the PF without significant difference with the 90th percentile value (3.64 µg/kg) in the actual sample. However, the value was 16.62 µg/kg without considering the PF. This study establishes a methodology for the correct evaluation of the risk to bee larva of acetamiprid residues in bee pollen and honey sac contents and the residual levels in royal jelly.

Residual behavior and risk assessment of fluopyram, acetamiprid and chlorantraniliprole used individually or in combination on strawberry.

In this study, fluopyram (FOR), acetamiprid (ATP), and chlorantraniliprole (CAP) were used individually or in combination at the maximum recommended dose in greenhouse strawberries to research the dissipation dynamics and dietary risks. A multi-residue analytical method for FOR, ATP, and CAP in strawberries using UPLC-MS/MS integrated with the QuEChERS approach was developed with strong linearity (R2 ≧ 0.9990), accuracy (recoveries of 82.62 to 107.79%), and precision (relative standard deviations of 0.58% to 12.73%). The limits of quantification were 0.01 mg kg-1. Field results showed that the half-lives of FOR, ATP and CAP in strawberry fruits were 11.6-12.4 days, 6.1-6.7 days, and 10.9-11.7 days, respectively. The half-lives of the three investigated pesticides showed no significant difference when used individually or in combination. A risk assessment indicated that the dietary intake risks of the three pesticides in grown strawberries were 0.0041 to 7.63% whether applied alone or in combination, which demonstrated that the dietary intake risks of the three pesticides in grown strawberries could be negligible for Chinese male and female consumers, and that even though pesticides were used in combination, there was less cause for concern about the safety. This paper serves as a guide for the safe use of FOR, ATP, and CAP on greenhouse strawberries.

Exposure and risk assessment of acetamiprid in honey bee colonies under a real exposure scenario in Eucalyptus sp. landscapes.

Honey bee colonies have shown abnormal mortality rates over the last decades. Colonies are exposed to biotic and abiotic stressors including landscape changes caused by human pressure. Modern agriculture and even forestry, rely on pesticide inputs and these chemicals have been indicated as one of the major causes for colony losses. Neonicotinoids are a common class of pesticides used worldwide that are specific to kill insect pests, with acetamiprid being the only neonicotinoid allowed to be applied outdoors in the EU. To evaluate honeybees' exposure to acetamiprid under field conditions as well as to test the use of in-situ tools to monitor pesticide residues, two honeybee colonies were installed in five Eucalyptus sp. plantations having different area where Epik® (active substance: acetamiprid) was applied as in a common spraying event to control the eucalyptus weevil pest. Flowers, fresh nectar, honey bees and colony products samples were collected and analyzed for the presence of acetamiprid residues. Our main findings were that (1) acetamiprid residues were found in samples collected outside the spraying area, (2) the amount of residues transported into the colonies increased with the size of the sprayed area, (3) according to the calculated Exposure to Toxicity Ratio (ETR) values, spraying up to 22 % of honeybees foraging area does not harm the colonies, (4) colony products can be used as a valid tool to monitor colony accumulation of acetamiprid and (5) the use of Lateral Flow Devices (LFDs) can be a cheap, fast and easy tool to apply in the field, to evaluate the presence of acetamiprid residues in the landscape and colony products.

Toxicological assessment of sublethal dose of acetamiprid in male mice and the efficacy of quercetin.

Acetamiprid (ACP) is a neonicotinoid insecticide that is the most effective pesticide for crop protection as well as flea control in agricultural animals and pets in the world. The goal of this study was to look at the in vivo effects of a sublethal dose of ACP on hematotoxicity, oxidative stress, hepatotoxicity, nephrotoxicity, immunotoxicity, and histological alterations, as well as the role of quercetin (QE) in alleviating these effects. Twenty adult male mice were divided into four equal groups orally administered corn oil (control), QE (50 mg kg-1 b.wt.), ACP (1/10 LD50) or ACP plus QE for two weeks. The results showed that ACP significantly lowered the body weight gain, hematological indices, glutathione (GSH), and both cellular and humoral immunity, On the other hand, levels of lipid peroxidation (LPO), glutathione peroxidase (GPx), and liver and kidney marker values were considerably increased in male mice exposed to ACP. In addition, examination under light microscopic showed that ACP induces histological alterations in liver and kidney tissues. The results also revealed that treating intoxicated mice with QE significantly reduced the deleterious effects of ACP. In conclusion, current results show that ACP at the sub lethal dose poses toxic risks to the liver and kidneys, and QE as a natural material enhances antioxidant defenses, which can be used as a potential interventional therapy against negative effects of pesticides like ACP.

A Comparison of Pollen and Syrup Exposure Routes in Bombus impatiens (Hymenoptera: Apidae) Microcolonies: Implications for Pesticide Risk Assessment.

Bumble bees are important pollinators for both native plants and managed agricultural systems. Accumulating evidence has shown that pesticides, including neonicotinoids, can have a range of adverse effects on bumble bee health. Most laboratory studies that assess the effects of chronic neonicotinoid exposure on bumble bees use syrup as the delivery vehicle, rather than pollen. However, in the field, it is likely that bumble bees are exposed to neonicotinoids in both nectar (syrup) and pollen. To examine the potential for different effects based on the vehicle, we compared two studies of chronic exposure to the neonicotinoid acetamiprid in Bombus impatiens microcolonies. We examined correlations between microcolony endpoints and identified associations between the timing of colony pollen and syrup consumption and drone production. Furthermore, in line with previous results, we found that average drone weight was affected at a range of doses only when microcolonies were exposed to acetamiprid via pollen. In general, our analyses point to the importance of the treatment vehicle and suggest that critical effects on developing brood could be missed when neonicotinoid exposure occurs only through syrup.

Exposure assessment of neonicotinoid insecticides and their metabolites in Chinese women during pregnancy: A longitudinal study.

Neonicotinoid insecticides (NNIs) are the most widely used insecticides globally and ubiquitous in the environment, which has led to widespread human exposure. However, studies on internal exposure levels of NNIs and their metabolites in pregnant women are scarce. In this study, we measured nine parent NNIs and ten main metabolites in 1224 urine samples donated by 408 pregnant women at three trimesters. In the urine samples, the unadjusted vs. specific gravity (SG) adjusted median concentrations and detection frequencies (DFs) of desmethyl-acetamiprid (DM-ACE; 1.01 vs. 1.08 ng/mL; DF: 99.7%), 5-hydroxy-imidacloprid (5-hydroxy-IMI; 0.54 vs. 0.56 ng/mL; 98.5%), imidacloprid-olefin (IMI-olefin; 0.41 vs. 0.44 ng/mL; 99.3%), and desnitro-imidacloprid (DN-IMI; 0.12 vs. 0.12 ng/mL; 90.4%) were higher than their corresponding parent NNIs, acetamiprid (ACE; <0.01 vs. <0.01 ng/mL; 26.4%) and imidacloprid (IMI; 0.04 vs. 0.04 ng/mL; 69.9%). The unadjusted and SG-adjusted median concentrations of clothianidin (CLO), thiamethoxam (THM), and desmethyl-clothianidin (DM-CLO) were 0.05 vs. 0.07, 0.05 vs. 0.06, and 0.04 vs. 0.05 ng/mL, with the DFs of 61.0%, 57.5%, and 75.7%, respectively. The cumulative exposure level, imidacloprid-equivalent total NNIs (IMIeq), was generated by the relative potency factor approach considering the toxic effects of NNIs and their metabolites. The unadjusted IMIeq varied from 0.17 ng/mL (SG-adjusted: 0.20) to 1969 ng/mL (SG-adjusted: 1817) with a median of 14.1 ng/mL (SG-adjusted: 14.1). A decreased trend was observed in urinary NNIs and their metabolites throughout the three trimesters. Maternal age, educational level, and household income were related to the concentrations of NNIs and their metabolites. DM-ACE, 5-hydroxy-IMI, and IMI-olefin were significantly lower in winter than in autumn; DN-IMI, THM, CLO, and DM-CLO were significantly higher in both summer and autumn than in winter. The maximum estimated daily intake of IMIeq [34.8 µg/kg-body weight (bw)/d] was lower than the chronic reference dose of IMI (57 µg/kg-bw/d) currently recommended by the United States Environmental Protection Agency. Human health risk of exposure to NNIs and their main metabolites warranted further studies.

A nationwide study of occurrence and exposure assessment of neonicotinoid insecticides and their metabolites in drinking water of China.

Neonicotinoid insecticides (NNIs) are the most extensively used insecticides worldwide, threatening ecosystem and human health. However, nationwide studies of NNIs and their metabolites in drinking water are limited. In order to characterize the contamination status of NNIs in drinking water throughout China, we collected 884 drinking water samples including 789 tap water and 95 groundwater samples from 32 provinces (covering seven regions of mainland China: south, central, east, north, northeast, northwest, and southwest) and Hong Kong. Ten NNIs and six of their main metabolites were determined in the water samples. The relative potency factor method was used to assess the cumulative concentrations of NNIs and their metabolites (imidacloprid-equivalent total NNIs, IMIeq) based on the chronic reference doses (cRfDs) of the NNIs or the toxic effects of the mataboilites. The IMIeq varied among the studied regions, with a median concentration of 24.5 ng/L and a maximum concentration of 8,622 ng/L. The predominant NNIs in drinking water were acetamiprid (ACE) and imidacloprid (IMI). Compared with tap water derived from groundwater, much higher concentrations of IMIeq and NNIs were found in tap water derived from surface water. Different concentrations and patterns of NNIs in drinking water were observed in different regions, provinces, and capital cities, mainly due to regional and provincial differences in crop types and volumes of pesticide usage. The concentrations of NNIs in the drinking water of provincial capitals and small/medium cities were higher than the concentrations in rural areas. The estimated daily intake (EDI) of IMIeq was at least two orders of magnitude lower than the cRfD of IMI, while the NNIs in 16 drinking water samples exceeded the acceptable value (100 ng/L) recommended by the European Union. This study provided a nationwide profile of the occurrence of NNIs and their metabolites in the drinking water of China and the associated potential cumulative human health risks, taking into account of the toxicity differences between NNIs and their metabolites.

Dissipation behavior, residue distribution and dietary risk assessment of cyromazine, acetamiprid and their mixture in cowpea and cowpea field soil.

BACKGROUND: Cyromazine and acetamiprid are widely applied as pesticides in agriculture, causing increasing concerns about their residues in crops. In this study, cyromazine, acetamiprid and their mixture were applied to cowpea to investigate their degradation dynamics and perform a dietary risk assessment. RESULTS: The dissipation behavior of cyromazine and acetamiprid in the single- and mixed-pesticide groups followed first-order kinetics, with a linear correlation coefficient of 0.910 to 0.987. The half-lives of cyromazine and acetamiprid were 1.56-11.18 days in the four different matrices. The half-life of cyromazine in the mixed-pesticide group was similar to or even shorter than that in the single-pesticide group. The highest levels of cyromazine and acetamiprid in cowpea occurred with a preharvest interval of 7 days and after two or three applications. These levels are below the maximum residue limits recommended by the Chinese Ministry of Agriculture for cyromazine and acetamiprid in cowpea. The risk quotient of cyromazine and acetamiprid ranged from 0.0018 to 0.0418, and the national estimated short-term intake values of the cyromazine and acetamiprid were far below the acute reference dose as recommended by the European Food Safety Authority. CONCLUSION: These results suggest that the use of cyromazine and acetamiprid and a cyromazine-acetamiprid mixture in cowpea is safe under the Good Agricultural Practices for Chinese fields, and the use of a cyromazine-acetamiprid mixture affords even better results than the application of cyromazine alone. Moreover, the residue dynamics information will support the label claims for the application of cyromazine, acetamiprid and a cyromazine-acetamiprid mixture to cowpea fruit. © 2020 Society of Chemical Industry.

Health risk assessment of neonicotinoid insecticide residues in pistachio using a QuEChERS-based method in combination with HPLC-UV.

There is an increasing need to address the potential risks arising from combined exposures to multiple residues from pesticides in the diet. Pesticide residue-related pollution is a problem that arises because of the increased use of pesticides in agriculture to meet the growing demands of food production. In this study, pesticide residue data were obtained based on an optimized extraction method. For this purpose, we established a method based on quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction for simultaneous determination of imidacloprid (IMI) and acetamiprid (ACT) in pistachio nuts. The parameters influencing the QuEChERS method were the sample-to-water ratio and adsorbent amounts. As a result, both were optimized to improve the recovery of the analytes as well as the clean-up efficiency of the pistachio matrix. Our results indicated that a freeze-out step and use of primary and secondary amines as an adsorbent led to much cleaner chromatograms with lower baseline drift, without using graphitized carbon black and C18 -based adsorbent, which reduced both cost and time of analysis. Following extraction, the pesticide residues were separated and quantified by reverse-phase HPLC. For validation purposes, recovery studies were carried out using a concentration range from 20 to 2500 µg/L at nine levels. The suitable linearity, precision, and accuracy were obtained with HPLC-UV with recoveries of 70.37%-89.80% for IMI and 81.05%-113.57% for ACT, with relative standard deviations <12%. The validated method was successfully applied to the analysis of pistachio samples collected from a field trial to estimate maximum residue limits. There was no significant health risk for consumers via pistachio consumption.

Mobility and sorption assessment of selected pesticides in alluvial aquifer.

The objective of the paper was to use transport model of selected pesticides (carbendazim, acetamiprid and imidacloprid) in determination of linear sorption coefficients in alluvial aquifer. For constructing transport model, results of a field experiment at the location of Kovin-Dubovac drainage system in Serbia were used in order to set hydraulic parameters (hydraulic conductivity, aquifer layer thickness of the observed area, effective porosity etc.). The field experiment consisted of a tracer test during which concentrations of non-reactive tracer (Cl-) and selected pesticides (carbendazim, acetamiprid and imidacloprid) were monitored. For better characterization of hydraulic parameters, a pumping test was conducted at the observed well and results were used in designing transport model. Simulation model was constructed with Lizza groundwater flow software and W.O.D.A. (Well Outline and Design Aid) solver. Obtained linear sorption coefficients in the sand and gravel water-bearing layer were 0.14 mL g-1 for carbendazim and 0.11 mL g-1 for acetamiprid and imidacloprid. Results from this study are a unique insight into mobility of observed pesticides in the alluvial groundwater in natural conditions and can be used in contamination assessment for drinking water wells.

Neonicotinoids in raw, finished, and tap water from Wuhan, Central China: Assessment of human exposure potential.

Neonicotinoid insecticides (NNIs) are emerging insecticides compared to organophosphates and pyrethroids. Their occurrence in the environment is not well documented in China. In this study, raw water samples (n=20), finished water samples (n=20), and tap water samples (n=165) originating from the Han River and the Yangtze River in Wuhan, Central China, were collected during 2018 for the determination of the NNI residues. NNIs were found in all raw water samples with a median sum concentration of 27.7ng/L (range: 13.4-186ng/L). Higher concentrations of NNIs were found in July than in May, and higher NNIs were found in the Han River than in the Yangtze River. Most NNIs were not effectively removed during water treatment, except for acetamiprid and thiacloprid which decreased by 40.1% and 20.0%, respectively. At least three NNIs were detected in all tap water samples with the highest sum concentration of NNIs observed in July (median: 96.2ng/L, range: 16.7-138ng/L) among the studied months (median: 15.4, range: 2.59-138ng/L). The estimated daily intake of NNIs via tap water ingestion in July was 8.66ng/kg body weight/day for infants, about 4 times higher than that for adults. The concentrations observed in tap water are elevated in China relative to previous studies that were conducted in the USA and in Canada. This is the first study reporting residue levels of NNIs in China.

Assessment of acetamiprid-induced genotoxic effects in bone marrow cells of Swiss albino male mice.

Acetamiprid (ACE), a neonicotinoid insecticide, is widely used in agriculture either alone or in combination with other insecticides. A combined approach employing micronucleus test (MNT) and chromosomal aberrations (CA) assay was utilized to assess the genotoxic effects of ACE in bone marrow of Swiss albino male mice. Acetamiprid was administered i.p. daily at 4.6 and 2.3 mg/kg/day along with 3% gum acacia as negative control for 60 and 90 days and cyclophosphamide (50 mg/kg b.wt.) as positive control. ACE treatment resulted in a dose-dependent increase in the frequencies of micronuclei per cell and chromosomal aberrations in bone marrow cells. The increased micronuclei formation in total erythrocyte cells (immature PCEs and mature NCEs) was observed only at higher dose level (4.6 mg/kg b.wt.) administered for 90 days. The test also indicated the cytotoxic effect of higher dose level of pesticide by PCE/NCE ratio. The number of chromosomal aberrations were increased in the pesticide treated group compared to the negative control group, although significant increase was observed only in the group exposed to higher dose level of pesticide for both 60 and 90 days. Thus, daily exposure of ACE at a dose level of 4.6 mg/kg body weight for 60 and 90 days caused genotoxic and cytotoxic effects on the somatic cells of Swiss albino male mice.

Analysis of multiple pesticide residues in polyphenol-rich agricultural products by UPLC-MS/MS using a modified QuEChERS extraction and dilution method.

An efficient method for the rapid extraction and clean-up of 20 pesticide residues from polyphenol-rich agricultural samples (tea, apple, broccoli, and shallot) for analysis by UPLC-MS/MS was developed. Following extraction, PVPP was used to precipitate polyphenols, supernatant was diluted to minimize matrix effects. Homogenized samples were vortexed in acetonitrile prior to cleanup with a combination of PVPP (150 mg), PSA (50 mg) and GCB (10 mg). Supernatant (1 mL) was filtered and diluted 10-fold before analysis. In 4 agricultural products that usually produce high interference, the matrix effects were overcome for all pesticides expect in green and oolong tea for acephate, omethoate, dinotefuran and nitenpyram. Mean recoveries ranged from 73% to 106%, and RSD ≦ 13%. Limits of quantification ranged from 0.01 to 0.02 mg kg-1. PVPP as one of excellent QuEChERS material combined with dilution was verified as a promising method for multiple pesticide residues analysis in complex matrices.

Toxicological assessment of lambda-cyhalothrin and acetamiprid insecticides formulated mixture on hatchability rate, histological aspects, and protein electrophoretic pattern of Biomphalaria alexandrina (Ehrenberg, 1831) snails.

Several formulated mixtures of pesticides are widely used in modern agriculture. Nevertheless, the agriculture runoff causes a serious damage to the aquatic ecosystem. Therefore, the present study aims to use B. alexandrina snails as bioindicators for 30 g/l lambda-cyhalothrin and 17 g/l acetamiprid as a formulated mixture insecticide. Results showed that it has a molluscicidal activity against snails at LC50 7.9 mg/l. The hatchability percent of both treated 1-day-aged and/or 3-day-aged groups were less than that of the control group. The sublethal concentrations of the tested insecticide caused a remarkable abnormal necrosis in male and female gametogenic cells, besides a severe damage in both secretory and digestive cells. The results of SDS-PAGE protein profiles of treated snails showed that the least number of protein bands was noticed in snail groups that subjected to LC10 (6.6 mg/l) and LC25 (7.2 mg/l) concentrations when compared to control protein fractions.

Focussed assessment of certain existing MRLs of concern for acetamiprid and modification of the existing MRLs for table olives, olives for oil production, barley and oats.

In compliance with Article 43 of Regulation (EC) No 396/2005, EFSA received from the European Commission a mandate to provide its reasoned opinion on the existing maximum residue levels (MRLs) for acetamiprid which might lead to consumers intake concerns on the basis of the new toxicological reference values agreed upon by Member States (MSs) in October 2017. In order to identify the MRLs of potential concern that require a more detailed assessment, EFSA performed a preliminary risk assessment, identifying a risk for consumers for 12 commodities. Measures for reduction of the consumer exposure were assessed by EFSA and should be considered by risk managers. Furthermore, in accordance with Article 6 of Regulation (EC) No 396/2005, ADAMA Makhteshim Ltd submitted two requests to modify the existing MRL for acetamiprid in table olives, olives for oil production, barley and oats. The data submitted in support of the requests were found to be sufficient to derive MRL proposals for all crops under assessment. Based on the risk assessment results, EFSA concluded that the short-term and long-term intake of residues resulting from the use of acetamiprid according to the intended agricultural practices on table olives, olives for oil production, barley and oats is unlikely to present a risk to consumer health.

Optimization of photochemical decomposition acetamiprid pesticide from aqueous solutions and effluent toxicity assessment by Pseudomonas aeruginosa BCRC using response surface methodology.

Contamination of water resources by acetamiprid pesticide is considered one of the main environmental problems. The aim of this study was the optimization of acetamiprid removal from aqueous solutions by TiO2/Fe3O4/SiO2 nanocomposite using the response surface methodology (RSM) with toxicity assessment by Pseudomonas aeruginosa BCRC. To obtain the optimum condition for acetamiprid degradation using RSM and central composite design (CCD). The magnetic TiO2/Fe3O4/SiO2 nanocomposite was synthesized using co-precipitation and sol-gel methods. The surface morphology of the nanocomposite and magnetic properties of the as-synthesized Fe3O4 nanoparticles were characterised by scanning electron microscope and vibrating sample magnetometer, respectively. In this study, toxicity assessment tests have been carried out by determining the activity of dehydrogenase enzyme reducing Resazurin (RR) and colony forming unit (CFU) methods. According to CCD, quadratic optimal model with R2 = 0.99 was used. By analysis of variance, the most effective values of each factor were determined in each experiment. According to the results, the most optimal conditions for removal efficiency of acetamiprid (pH = 7.5, contact time = 65 min, and dose of nanoparticle 550 mg/L) was obtained at 76.55%. Effect concentration (EC50) for RR and CFU test were 1.950 and 2.050 mg/L, respectively. Based on the results obtained from the model, predicted response values showed high congruence with actual response values. And, the model was suitable for the experiment's design conditions.

A simple and rapid chemiluminescence aptasensor for acetamiprid in contaminated samples: Sensitivity, selectivity and mechanism.

Ultralow concentration and selective detection of pesticide residue is important to evaluate the environmental and biological pollution and the threat to human health which single component pesticide can bring. Herein, we report an amplified chemiluminescence (CL) sensing platform for ultrasensitive and selective acetamiprid (widely used pesticide) detection. It is based on aptamer's high binding affinity to target and the relevance between AuNPs' morphology and its catalytic effect to stimulate the generation of CL in the presence of H2O2 and luminol. Moreover, AuNPs morphological slight change induced by aptamers' conformation during targets binding could lead to the significant change of catalytic properties. Therefore, the proposed sensing platform for pesticide residue exhibited a high sensitivity toward acetamiprid with a detection limit of 62pM, which was about 100-fold lower than that of other aptamer-based sensor for acetamiprid detection. Because of the intrinsic specificity of aptamer's recognization, this sensing platform has high selectivity. So, this sensing platform provides a label-free and cost-effective approach for sensitive and selective detection of single component pesticide residue. More importantly, this CL method was successfully used to determine acetamiprid in real contaminated samples.

A facile label-free colorimetric aptasensor for acetamiprid based on the peroxidase-like activity of hemin-functionalized reduced graphene oxide.

A facile aptasensor has been developed for the colorimetric detection of acetamiprid by using the hemin-functionalized reduced graphene oxide (hemin-rGO) composites. The as-prepared hemin-rGO composites possessed both the ability of rGO to physically adsorb the aptamers and the peroxidase-like activity of hemin that could catalyse 3,3,5,5-tetramethylbenzidine (TMB) in the presence of H2O2, to produce a solution with blue color. The well-dispersed hemin-rGO composites coagulated completely at the proper salt concentration; however, the coagulation of hemin-rGO was vanished when abundant aptamers were adsorbed on its surface because the attached negatively charged DNA backbone increased individual hemin-rGO electrostatic repulsion. In the detection scheme, acetamiprid with different concentrations was firstly incubated with the same amount of aptamer. The more acetamiprid in the tested solution, the less free aptamers were absorbed on the hemin-rGO surface, making the composites coagulate to a higher degree in the presence of the optimum NaCl concentration. As a consequence, the content of hemin-rGO in the supernatant was decreased after centrifugation, which catalysed oxidation of TMB in the presence of H2O2 to produce light blue color with a low absorbance. The color variation relavant to the acetamiprid concentration can be judged by the naked eyes and easily monitored by the inexpensive UV-vis spectrometer. Such designed aptasensor displayed a linear response for acetamiprid in the range from 100nM to 10µM with a detection limit of 40nM (S/N=3). This colorimetric aptasensing platform offers great advantages including the simple operation process, low-cost portable instrument, and user-friendly applications.