Column switching liquid chromatography and post-column photochemically fluorescence detection to determine imidacloprid and 6-chloronicotinic acid in honeybees

Green synthesis of novel magnetic porous organic polymer for magnetic solid phase extraction of neonicotinoids in lemon juice and honey samples

Natural rutin with abundant hydroxyl groups was used as a green monomer to synthesize hydroxyl-functional magnetic porous organic polymer (named Rut-MOP) through environmentally-benign diazo-coupling reaction for the first time. The Rut-MOP displayed high extraction capability for neonicotinoid insecticides (thiamethoxam, imidacloprid, acetamiprid and thiacloprid). Thus, a Rut-MOP based magnetic solid-phase extraction method combined with high performance liquid chromatography was established for sensitive determination of neonicotinoid insecticides in lemon juice and honey samples. Under optimized conditions, the linear response of neonicotinoids was 0.1-100.0 ng mL^-1 for lemon juice and 8.0-1000.0 ng g^-1 for honey. The limits of detection (S/N = 3) were 0.03-0.04 ng mL^-1 and 2.5-3.0 ng g^-1 for lemon juice and honey, respectively. The method recoveries were 82-118% with the relative standard deviations of 1.9-7.6%. The results demonstrate that the Rut-MOP based method can be served as a good alternative for the sensitive analysis of neonicotinoid insecticides in lemon juice and honey.

Simultaneous determination of acetamiprid and 6-chloronicotinic acid in environmental samples by using ion chromatography hyphenated to online photoinduced fluorescence detector

This study aims to introduce a simple, sensitive, and cost-effective method for the simultaneous determination of acetamiprid and its main metabolite 6-chloronicotinic acid in environmental samples by using a nonsuppressed ion chromatography hyphenated with an online postcolumn photoinduced fluorescence detection system. The fluorescence detector wavelengths λ_ex /λ_em  = 257/382 nm was set for up to 6.0 min for acetamiprid, while λ_ex /λ_em  = 231/370 nm programmed for 6-chloronicotinic acid for the rest of the analysis time. Both samples were treated by applying miniaturized quick, easy, cheap, effective, rugged, and safe method before the separation of analytes on an IonPac^® AS11-HC column by pumping 40 mM NaOH having minuscule content of acetonitrile (5%, v/v) as an eluent. Both intrinsically nonfluorescent analytes were turned-on by online postcolumn photoinduced derivatization, avoiding the need for complex chemical derivatization or addition of a postcolumn extra pump. The developed method was appraised for the analysis of environmental samples, exhibiting excellent linearity (0.050-10 μg/mL) with a correlation coefficient greater than 0.9993 for both analytes. Whereas, obtained limit of detection (0.025-0.0072 μg/mL), recoveries (98.02-116.00%), and inter- and intraday precision (≤3.02 %) were satisfactory for both compounds in environmental samples.

An Eco-Friendly Hydrophobic Deep Eutectic Solvent-Based Dispersive Liquid-Liquid Microextraction for the Determination of Neonicotinoid Insecticide Residues in Water, Soil and Egg Yolk Samples

A green, simple and sensitive hydrophobic DES-based dispersive liquid–liquid microextraction coupled with high-performance liquid chromatography (HPLC) was developed for the analysis of neonicotinoid insecticide residues in various samples. A hydrophobic deep eutectic solvent (DES) was synthesized using decanoic acid as a hydrogen bond donor and tetrabutylammonium bromide (TBABr) as a hydrogen bond-acceptor. DESs were synthesized and characterized by Fourier transform-infrared (FTIR) spectroscopy. Two disperser solvents were substituted with surfactants and acetonitrile, which could afford more effective emulsification and make the extraction relatively greener. The hydrophobic DES extraction phase occurred 10 min after centrifugation, being easy to be collected for analysis. Several parameters were investigated and optimized. Under the optimum condition, the calibration curve of this method was linear in the range of 0.003–1.0-µg·mL⁻¹, with a correlation coefficient (R²) higher than 0.99 and a good repeatability, with the relative standard deviations (RSDs) were less than 5.00%. The limits of detection were in the range of 0.001–0.003 µg·mL⁻¹; the limits of quantitation were in the range of 0.003–0.009 µg·mL·mL⁻¹. Finally, the presented method was implemented to determine the neonicotinoid insecticide residues in water, soil, egg yolk samples and acceptable recoveries were obtained.

A functionalized magnetic covalent organic framework for sensitive determination of trace neonicotinoid residues in vegetable samples

A functionalized magnetic covalent organic framework containing the nitro groups (Fe₃O₄@COF-(NO₂)₂) with core-shell structure was synthesized for magnetic solid phase extraction (MSPE) of six neonicotinoid insecticides residue in vegetable samples. The structure of Fe₃O₄@COF-(NO₂)₂ was investigated by various characterization techniques. The Fe₃O₄@COF-(NO₂)₂ exhibits the excellent thermal and chemical stability, high surface area (254.72 m² g^-1), total pore volume (0.19 cm³ g^-1), high magnetic responsivity (27.7 emu g^-1), which can be used as an ideal adsorbent for rapid isolation and enrichment of target analytes. A sensitive method was developed by using Fe₃O₄@COF-(NO₂)₂-based MSPE coupled with HPLC with UV detection. It offered good linearity within the range of 0.1-30 ng mL^-1, low limits of detection (S/N = 3) of 0.02-0.05 ng mL^-1. Furthermore, high enrichment factors of 170-250 for six neonicotinoid insecticides were obtained. The applicability of Fe₃O₄@COF-(NO₂)₂ is demonstrated for measuring trace neonicotinoid residues in vegetable samples with satisfactory recoveries, which ranged from 77.5 to 110.2%. The results indicated that the Fe₃O₄@COF-(NO₂)₂ microspheres offer great potential for efficient extraction of neonicotinoid insecticides from complex samples.

Comparison of two different nickel oxide films for electrochemical reduction of imidacloprid

A nickel oxide (NiO) thin film was successfully prepared on Ni foil via a sol–gel method and a reduced state nickel oxide (r-NiO) thin film was obtained by etching NiO with hydrazine hydrate solution.

Determination of nitenpyram and 6-chloronicotinic acid in environmental samples by ion chromatography coupled with online photochemically induced fluorescence detector

A simple, cost-effective, sensitive, and quick method for the determination of nitenpyram and its metabolite 6-chloronicotinic acid in environmental samples was developed by coupling an ion chromatograph with a fluorescence detector and a post-column photochemical reactor. This developed analytical method involved a rapid sample extraction by modified and miniaturized quick, easy, cheap, effective, rugged, and safe method followed by isocratic ion chromatographic separation of nitenpyram and 6-chloronicotinic acid into an IonPac^™ AS11-HC column protected by IonPac^™ AG11A guard column by running 30 mM NaOH + 10% acetonitrile mobile phase. A homemade post-column photochemical reactor was also integrated with the ion chromatographic system for online transformation of both analytes into their respective highly fluorescent photoproduct in basic media without using an extra pump. The developed method was validated by following SANTE/11945/2015 guidelines on analytical quality control and validation procedures. The method showed a good linear response (r > 0.999), improved limit of detection (0.101-0.132 μg/L), minimum or no matrix effect, excellent recoveries (90.2-100.10%) and relative standard deviations were found to be ≤6.50%.

Preconcentration of Trace Neonicotinoid Insecticide Residues Using Vortex-Assisted Dispersive Micro Solid-Phase Extraction with Montmorillonite as an Efficient Sorbent

In this work, we investigated montmorillonite for adsorption of neonicotinoid insecticides in vortex-assisted dispersive micro-solid phase extraction (VA-d-μ-SPE). High-performance liquid chromatography with photodiode array detection was used for quantification and determination of neonicotinoid insecticide residues, including thiamethoxam, clothianidin, imidacloprid, acetamiprid, and thiacloprid. In this method, the solid sorbent was dispersed into the aqueous sample solution and vortex agitation was performed to accelerate the extraction process. Finally, the solution was filtered from the solid sorbent with a membrane filter. The parameters affecting the extraction efficiency of the proposed method were optimized, such as amount of sorbent, sample volume, salt addition, type and volume of extraction solvent, and vortex time. The adsorbing results show that montmorillonite could be reused at least 4 times and be used as an effective adsorbent for rapid extraction/preconcentration of neonicotinoid insecticide residues. Under optimum conditions, linear dynamic ranges were achieved between 0.5 and 1000 ng mL^-1 with a correlation of determination (R²) greater than 0.99. Limit of detection (LOD) ranged from 0.005 to 0.065 ng mL^-1, while limit of quantification (LOQ) ranged from 0.008 to 0.263 ng mL^-1. The enrichment factor (EF) ranged from 8 to 176-fold. The results demonstrated that the proposed method not only provided a more simple and sensitive method, but also can be used as a powerful alternative method for the simultaneous determination of insecticide residues in natural surface water and fruit juice samples.

Comprehensive two-dimensional ion chromatography (2D-IC) coupled to a post-column photochemical fluorescence detection system for determination of neonicotinoids (imidacloprid and clothianidin) in food samples

There are increasing concerns about the dietary risks of neonicotinoids (NNIs); therefore their sensitive and accurate determination in dietary products is indispensable. However, the complex composition of agricultural food matrixes makes their extraction and quantitative determination a challenging task. Realizing this need, we herein report a simple, cost-effective, selective and sensitive fluorescence analytical workflow for analyses of two non-fluorescent neonicotinoids imidacloprid (IMI) and clothianidin (CLT) in six complex food samples (honey, ginger, durian, apple, tomato, cucumber) by online clean-up of sample extracts using two-dimensional ion chromatography (2D-IC) and a subsequent online post column UV induced fluorescence detection system. This online clean-up setup has proven advantageous to improve the limit of detection, potentially diminish matrix effects, and reduce analysis time and labor. The developed method showed excellent analytical figures of merit including linearity, selectivity, repeatability, recovery, and resolution for analysis of IMI and CLT in food samples.

A 2D-IC system was successfully fabricated for clean isocratic chromatographic separations and sensitive post column UV induced fluorescence determination of two NNIs in six complex food samples.

The exposure of honey bees (Apis mellifera; Hymenoptera: Apidae) to pesticides: Room for improvement in research

Losses of honey bees have been repeatedly reported from many places worldwide. The widespread use of synthetic pesticides has led to concerns regarding their environmental fate and their effects on pollinators. Based on a standardised review, we report the use of a wide variety of honey bee matrices and sampling methods in the scientific papers studying pesticide exposure. Matrices such as beeswax and beebread were very little analysed despite their capacities for long-term pesticide storage. Moreover, bioavailability and transfer between in-hive matrices were poorly understood and explored. Many pesticides were studied but interactions between molecules or with other stressors were lacking. Sampling methods, targeted matrices and units of measure should have been, to some extent, standardised between publications to ease comparison and cross checking. Data on honey bee exposure to pesticides would have also benefit from the use of commercial formulations in experiments instead of active ingredients, with a special assessment of co-formulants (quantitative exposure and effects). Finally, the air matrix within the colony must be explored in order to complete current knowledge on honey bee pesticide exposure.

Ringer tablet-based ionic liquid phase microextraction: Application in extraction and preconcentration of neonicotinoid insecticides from fruit juice and vegetable samples

An efficient, reliable, sensitive, rapid, and green analytical method for the extraction and determination of neonicotinoid insecticides in aqueous samples has been developed using ionic liquid phase microextraction coupled with high performance liquid chromatography-diode array detector. In this method, a few microliters of 1-hexyl-3-methylimidazolium hexafluorophosphate (as an extractant) is added onto a ringer tablet and it is transferred into a conical test tube containing aqueous phase of the analytes. By manually shaking, the ringer tablet is dissolved and the extractant is released into the aqueous phase as very tiny droplets to provide a cloudy solution. After centrifuging the extracted analytes into ionic liquid are collected at the bottom of a conical test tube. Under the optimum extraction conditions, the method showed low limits of detection and quantification between 0.12 and 0.33 and 0.41 and 1.11ngmL(-1), respectively. Extraction recoveries and enrichment factors were from 66% to 84% and 655% to 843%, respectively. Finally different aqueous samples were successfully analyzed using the proposed method.

Simultaneous determination of three neonicotinoid insecticide residues and their metabolite in cucumbers and soil by QuEChERS clean up and liquid chromatography with diode-array detection

A new method was developed for the simultaneous determination of three neonicotinoid insecticides with their metabolite in cucumbers and soil based on QuEChERS as a pretreatment procedure.

Development of a simple extraction and oxidation procedure for the residue analysis of imidacloprid and its metabolites in lettuce using gas chromatography

Simple extraction and optimised oxidation procedures were developed for the determination of the total residues of imidacloprid and its metabolites (containing the 6-chloropicolyl moiety) in lettuce using a gas chromatography-micro electron capture detector (GC-μECD). Samples were extracted with acetonitrile, and the extract was then evaporated. The remaining residues were dissolved in water and oxidised with potassium permanganate to yield 6-chloronicotinic acid (6-CAN). The acid residues were further dissolved in n-hexane:acetone (8:2, v/v) and then silylated with MSTFA (N-methyl-N-(trimethylsilyl)trifluoroacetamide) to 6-chloronicotinic acid trimethylsilyl ester. Calibration curves were linear over the concentration ranges (0.025-5 μg mL(-1)) with a determination coefficient (r(2)) of 0.991. The limits of detection and quantification were 0.015 and 0.05 mg kg(-1), respectively. Recoveries at two fortification levels ranged between 72.8% and 108.3% with relative standard deviation (RSD) lower than 8%. The method was effective, and sensitive enough to determine the total residues of imidacloprid and its metabolites in field-incurred lettuce samples. The identity of the analyte was confirmed using gas chromatography-tandem mass spectrometry (GC-MS/MS).

The development, validation and application of a GC-dual detector (NPD-ECD) multi-pesticide residue method for monitoring bee poisoning incidents

A simple multiresidue method based on matrix solid phase dispersion (MSPD) combined with clean-up has been developed for the simultaneous screening of 153 pesticides in honeybees suspected of suffering from pesticide poisoning during field spraying. Extraction and clean-up were carried out in a glass column containing anhydrous sulphate, 2.0g of octadecyl (C18) and a 2.0-g sample of bees (23 insects on average) macerated with 4.0g of Florisil. An additional layer of anhydrous sodium sulphate was added, and acetonitrile was used as the elution solvent. This combination of clean-up steps ensured an efficient purification. A gas chromatograph with dual selective detectors for electron capture and nitrogen-phosphorous was used. The results presented in this paper demonstrate that matrix solid-phase dispersion (MSPD) with the one-step clean-up procedure is the most effective extraction technique. MSPD method recoveries ranged from 70 to 118%, with precision values expressed as a relative standard of <20%, except for 10 pesticides that had recoveries of 50-70% and two with 120-130%. Low limits of detection (0.003-0.04μg/g) and quantification (0.005-0.05μg/g) were readily achieved with this method for all tested pesticides. A "top down" empirical model was used to estimate the expanded uncertainty at 28% on average (coverage factor k=2, confidence level 95%). The MSPD method was successfully used on real bee samples to analyse four acaricides, 55 fungicides, 16 herbicides and 78 insecticides from various regions of Poland. A total of 33 honeybee samples from suspected pesticide poisoning incidents were analysed, in which 17 different pesticides were determined (14 insecticides and three fungicides). The pesticides most often found in honeybees were cypermethrin (in 51% of the samples, 0.008-0.563µg/bee), chlorpyrifos (27%, 0.001-51.5µg/bee) and biphentin (21%, 0.002-0.012µg/bee).

Acetylcholinesterase in honey bees (Apis mellifera) exposed to neonicotinoids, atrazine and glyphosate: laboratory and field experiments

In Québec, as observed globally, abnormally high honey bee mortality rates have been reported recently. Several potential contributing factors have been identified, and exposure to pesticides is of increasing concern. In maize fields, foraging bees are exposed to residual concentrations of insecticides such as neonicotinoids used for seed coating. Highly toxic to bees, neonicotinoids are also reported to increase AChE activity in other invertebrates exposed to sub-lethal doses. The purpose of this study was therefore to test if the honey bee's AChE activity could be altered by neonicotinoid compounds and to explore possible effects of other common products used in maize fields: atrazine and glyphosate. One week prior to pollen shedding, beehives were placed near three different field types: certified organically grown maize, conventionally grown maize or non-cultivated. At the same time, caged bees were exposed to increasing sub-lethal doses of neonicotinoid insecticides (imidacloprid and clothianidin) and herbicides (atrazine and glyphosate) under controlled conditions. While increased AChE activity was found in all fields after 2 weeks of exposure, bees close to conventional maize crops showed values higher than those in both organic maize fields and non-cultivated areas. In caged bees, AChE activity increased in response to neonicotinoids, and a slight decrease was observed by glyphosate. These results are discussed with regard to AChE activity as a potential biomarker of exposure for neonicotinoids.

Study on the interaction between nucleic acids and imidacloprid and its application

The determination of imidacloprid with DNA via a resonance light scattering (RLS) technique was developed. The RLS of DNA was remarkably quenched after adding imidacloprid in aqueous medium of pH 2.10. An RLS peak at 311 nm was found, and the quenched intensity of RLS at this wavelength was proportional to the concentration of imidacloprid. The linear range of the calibration curve was approximately 0.02-2 microg/mL with the detection limit (S/N = 3) of 0.02 ng/mL. The imidacloprid in river water, cucumbers, and apple samples was determined. The recovery rates were in the range of 91.9% to 95.20%, 97.2% to 111.3%, and 94.5% to 114.8%, respectively. The mechanism of the reaction between imidacloprid and DNA is also discussed.

Simultaneous determination of seven neonicotinoid pesticide residues in food by ultraperformance liquid chromatography tandem mass spectrometry

The present study developed an improved analytical method for simultaneous quantification of seven neonicotinoids in food by ultraperformance liquid chromatography combined with electrospray ionization triple quadrupole tandem mass spectrometry (UPLC-MS/MS) under the multiple reaction monitoring (MRM) mode. The optimization of extraction, cleanup, UPLC separation and MS/MS parameters of analytes were especially focused on. The low limits of quantification (LOQs) of neonicotinoids ranged from 0.1 to 6 microg kg(-1). Meanwhile, reasonable recoveries (65-120%) of seven neonicotinoids for food including apple, cabbage, potato, rice, tea, milk, chicken, pork and egg were demonstrated in different spiked levels within their respective linear range (0.025-150 microg kg(-1)). The developed analytical method would be appropriate for the routine, high throughput, high sensitivity quantification of seven neonicotinoids using simple sample pretreatment.

A rapid spectrophotometric determination of imidacloprid in selected commercial formulations in the presence of 6-chloronicotinic acid

A simple first-order derivative spectrophotometric method was developed for the simultaneous determination of imidacloprid and 6-chloronicotinic acid (6-CNA). By using the zero-crossing approach, imidacloprid was determined at 249 nm and 6-CNA at 236 nm with detection limits of 0.32 and 0.17 ?g mL-1, respectively, and relative standard deviations not exceeding 1.2 % in the case of model systems. The proposed method was applied for the determination of imidacloprid and 6-CNA in commercial formulations. A conventional spectrophotometric method (at 270 nm) was also employed for the determination of the content of imidacloprid in the same commercial formulations. The results of the developed spectrophotometric methods were in good agreement with those obtained by the high-performance liquid chromatographic method.

Enhanced fluorescence detection of cis-combretastatins by post-column photolysis

A method is described to enhance the sensitivity of fluorescence detection of cis-combretastatins using a short post-column photolysis coil with a mercury lamp, by inducing the rapid conversion to the trans isomer. Although all the compounds studied showed enhanced fluorescence after photolysis, there were large differences in the absolute level, with the inherent response of the catechol CA1 being much lower than the corresponding phenolic CA4. Brief exposure to the deuterium lamp in a photodiode array detector also resulted in significant enhancement.