Use of High-Performance Liquid Chromatography?UV and Gas Chromatography?Mass Spectrometry for Determination of the Imidacloprid Content of Honeybees, Pollen, Paper Filters, Grass, and Flowers

A Rapid Immunochromatographic Method Based on Gold Nanoparticles for the Determination of Imidacloprid on Fruits and Vegetables

Imidacloprid (IMP) is toxic and a potential carcinogen that is most widely used as an insecticide for pest control and seed treatment. It is important to produce a rapid and sensitive assay for on-site monitoring. We have developed a novel lateral flow assay (LFA) using a sensitive monoclonal antibody (mAb) for monitoring IMP residues on fruits and vegetables. The 50% inhibition concentration result that was found when using the ELISA method was 0.247 ng mL^-1, with the cut-off limits using the LFA method the result was 10 ng mL^-1 (0.01 M PBS), and in the samples it was 20 ng mL^-1 (with a recovery rate of 96-104.7% for Chinese cabbage, cowpea, apple, and pear samples, respectively). All of the results can be determined within seven minutes. The proposed LFA method is a valid, quick, and stable assay for the on-site detection of IMP in large numbers of samples.

A QuEChERS-HPLC-MS/MS Method with Matrix Matching Calibration Strategy for Determination of Imidacloprid and Its Metabolites in Procambarus clarkii (Crayfish) Tissues

We developed a method for determination of imidacloprid and its metabolites 5-hydroxy imidacloprid, olefin imidacloprid, imidacloprid urea and 6-chloronicotinic acid in Procambarus clarkii (crayfish) tissues using quick, easy, cheap, effective, rugged, and safe (QuEChERS) and high-performance liquid chromatography-triple quadrupole mass spectrometry. Samples (plasma, cephalothorax, hepatopancrea, gill, intestine, and muscle) were extracted with acetonitrile containing 0.1% acetic acid and cleaned up using a neutral alumina column containing a primary secondary amine. The prepared samples were separated using reverse phase chromatography and scanned in the positive and negative ion multiple reaction-monitoring modes. Under the optimum experimental conditions, spiked recoveries for these compounds in P. clarkii samples ranged from 80.6 to 112.7% with relative standard deviations of 4.2 to 12.6%. The limits of detection were 0.02-0.5 μg·L^-1, the limits of quantification were 0.05-2.0 μg·L^-1 and the method of quantification was 0.05-2.0 μg·kg^-1. The method is rapid, simple, sensitive and suitable for rapid determination and analysis of imidacloprid and its metabolites in P. clarkii tissues.

Development of immunoassays with high sensitivity for detecting imidacloprid in environment and agro-products using phage-borne peptides

Imidacloprid is the most widely used neonicotinoid insecticide and has been reported to pose a threat to ecological security and human health. Therefore, simple-to-operate and highly sensitive methods for the detection of trace levels of imidacloprid are necessary. Here, we isolated two phage-borne peptides that compete with imidacloprid to bind the monoclonal antibody (mAb) 3D11 from phage display peptide libraries. A phage-enzyme-linked immunosorbent assay (P-ELISA) and two phage time-resolved fluoroimmunoassays (P-TRFIAs) for the detection of imidacloprid were developed using the phage-borne peptides as substitutes for chemically synthesized antigens. After systematic optimization, the half-maximum inhibition concentrations (IC₅₀) of the P-ELISA, P-TRFIA-1, and P-TRFIA-2 were 0.067 ng mL^-1, 0.085 ng mL^-1, and 0.056 ng mL^-1, respectively. Based on their IC₅₀ values, the sensitivities of the P-ELISA and P-TRFIAs were more than four times greater than those of previous immunoassays. Additionally, the immunoassays showed satisfactory recovery in the detection of spiked samples and good correlation with high performance liquid chromatography (HPLC) for the detection of samples containing incurred residues.

Analysis of Food by High Performance Liquid Chromatography Coupled with Coulometric Detection and Related Techniques: A Review

The development of single coulometric cells in combination with high performance liquid chromatography to dual cells and to the coulometric electrode array detector is described. An overview is given about the application of these methods in food chemistry. Easily oxidizable compounds, such as phenolic substances, pesticides, or vitamins, can be determined, as well as substances with high oxidation potentials or electroinactive compounds. Substances exhibiting poor electrochemical activity can be transformed to electroactive compounds by precolumn derivatization, postcolumn photochemical reactions, postcolumn enzyme reactors, or by using the oxidative/reductive mode for coulometric electrode array detection. Furthermore, it is shown that the interesting combination of high performance liquid chromatography with electrochemistry and mass spectrometry has opened further possibilities with respect to interpretation of redox reactions, drug metabolism studies, metabolomics, and electrochemical derivatization.

Liquid chromatography/tandem mass spectrometry analysis of neonicotinoids in environmental water

RATIONALE

Neonicotinoids (NNIs) are the fastest expanding group of pesticides in the world over the last two decades; however, they may be a significant contributing factor to bee mortality. The widespread use of NNIs makes it critical to monitor their residuals in the environment. Published methods for NNI analysis are mainly focused on agricultural and food products, and many of them only measured a portion of the commercially available NNIs.

METHODS

Utilizing a biphenyl stationary-phase column, a sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed to determine eight NNIs, including acetamiprid, clothianidin, dinotefuran, flonicamid, imidacloprid, nitempyram, thiacloprid and thiamethoxam in environmental water. Two multiple reaction monitoring (MRM) transitions were monitored for each compound to ascertain true positive identification. Isotope-labelled NNIs, d3-acetamiprid, d3-clothianidin, d4-imidacloprid and d3-thiamethoxam, were used to compensate for extraction efficiency, matrix effects and instrument variability while monitoring real-time method performance. Target compounds in aqueous samples were analyzed by direct aqueous injection (DAI) or after solid-phase extraction (SPE).

RESULTS

The method detection limits (MDLs) of NNIs in drinking water, surface water and groundwater were in the ranges of 50 to 190 and 2 to 7 ng/L for DAI and SPE procedures, respectively, and target compound recoveries ranged from 78 to 110%. The stability of target compounds in water samples and SPE extracts was also investigated for the first time to ensure accurate results. No obvious degradation was observed for target compounds within four weeks in either water samples or SPE extracts.

CONCLUSIONS

The method developed for neonicotinoid pesticide analysis is very sensitive and efficient. It provides good flexibility to meet various environmental monitoring needs and is employed for an extensive study to determine the distribution of NNIs in Ontario's water.

Determination of neonicotinoid insecticide residues in edible oils by water-induced homogeneous liquid–liquid extraction and dispersive liquid–liquid extraction followed by high performance liquid chromatography-diode array detection

Development of a new version of homogeneous liquid–liquid extraction based on water induced followed by dispersive liquid–liquid microextraction for extraction of neonicotinoid insecticides from oil samples.

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).

Liquid chromatography with diode array detection and tandem mass spectrometry for the determination of neonicotinoid insecticides in honey samples using dispersive liquid-liquid microextraction

The combination of solid-phase extraction with dispersive liquid-liquid microextraction (SPE-DLLME) is proposed for the determination of five neonicotinoid insecticides in honey. After a cleanup stage, the analytes were eluted using acetonitrile. DLLME was performed by injecting rapidly the acetonitrile extract into 10 mL of water containing a 10% (w/v) NaCl and 100 μL of CHCl3. The settled organic phase obtained after centrifugation was evaporated, reconstituted in acetonitrile (ACN), and submitted to liquid chromatography (LC) with photodiode array detection (DAD) and atmospheric pressure chemical ionization-ion trap-tandem mass spectrometry (APCI-IT-MS/MS). The matrix effect was evaluated, and quantification was carried out using external aqueous calibrations when using DAD, the matrix-matched calibration method was applied for MS/MS. Detection limits in the 0.2-1.0 and 0.02-0.13 ng/g ranges were obtained when using DAD and MS/MS, respectively. The SPE-DLLME-LC-APCI-IT-MS/MS method was applied for the analysis of different honey samples, and none was found to contain residues.

UHPLC/MS-MS Analysis of Six Neonicotinoids in Honey by Modified QuEChERS: Method Development, Validation, and Uncertainty Measurement

Rapid and reliable multiresidue analytical methods were developed and validated for the determination of 6 neonicotinoids pesticides (acetamiprid, clothianidin, imidacloprid, nitenpyram, thiacloprid, and thiamethoxam) in honey. A modified QuEChERS method has allowed a very rapid and efficient single-step extraction, while the detection was performed by UHPLC/MS-MS. The recovery studies were carried out by spiking the samples at two concentration levels (10 and 40 μg/kg). The methods were subjected to a thorough validation procedure. The mean recovery was in the range of 75 to 114% with repeatability below 20%. The limits of detection were below 2.5 μg/kg, while the limits of quantification did not exceed 4.0 μg/kg. The total uncertainty was evaluated taking the main independent uncertainty sources under consideration. The expanded uncertainty did not exceed 49% for the 10 μg/kg concentration level and was in the range of 16–19% for the 40 μg/kg fortification level.

Survey of neonicotinoids and fipronil in corn seeds for agriculture

Recently, legislative decisions withdrew or temporarily suspended the use of neonicotinoids and fipronil as seeds tanning in many countries because of their endocrine-disrupting activity imputable to the bees' toxicity. In this study, the occurrence of acetamiprid, fipronil, clothianidin, flonicamid, imidacloprid, nitenpyram, thiacloprid and thiamethoxam was detected in 66 samples of commercial treated corn seeds, collected in the Italian market in the frame of ministerial institutional quality control activity. Because of the lack of a validated analytical protocol for neonicotinoid detection in seeds, a routinely suitable liquid chromatography-tandem mass spectroscopy (LC-MS/MS) analytical method was developed and statistically validated on fortified corn seeds. Survey results demonstrated that 88% of the investigated seed samples showed the presence of residues of clothianidin, fipronil, thiamethoxam and thiacloprid, either individually or simultaneously, with values that ranged from about 0.002 to 20 mg kg(-1), which evidenced the alarming illicit use of these pesticides in seed treatments.

Development of fluorescence polarization immunoassay for the rapid detection of 6-chloronicotinic acid: main metabolite of neonicotinoid insecticides

A fluorescence polarization immunoassay (FPIA) for the quantitative determination of 6-chloronicotinic acid (6-CNA) using polyclonal antibody was developed. The 6-CNA-protein (bovine serum albumin and soybean trypsin inhibitor) conjugates and fluorescein-labeled 6-CNA derivative (tracer) were prepared and used as the immunogens and tracer, respectively. The synthesized tracer was purified by thin layer chromatography (TLC) and showed a good binding to antiserum (73/5) which was obtained from the immunized rabbit (No. 73) with 6-CNA-BSA conjugate. The detection limit (10% inhibition) of FPIA was 4 microg/mL, and IC(50) value was 32 microg/mL. The FPIA showed a cross-reaction for 5-amino-2-chloropyridine (60%), but no cross-reaction for other pesticides was observed. Recoveries for spiked apple, urine, soil, and water samples (5, 50, and 500 ppm) averaging between 78.6 +/- 8.8 and 114 +/- 18% were reasonable and in good agreement with the amounts spiked. Although the developed FPIA possesses low sensitivity, this assay is more simple and quick than other analytical methods, such as high performance liquid chromatography and gas chromatography. Thus, the developed FPIA method could be a useful tool for express screening 6-CNA in agricultural, environmental, and biological samples.

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

The determination of imidacloprid and its main metabolite (6-chloronicotinic acid) in honeybees was performed by liquid chromatography with post-column photochemical derivatisation in alkaline medium and fluorescence detection. The compounds were extracted from honeybees with acetone under ultrasound conditions prior to liquid-liquid partition with dichloromethane. The separation of extract components was performed using a 50 mm x 4.6 mm i.d. short column packed with 5 microm Aquasil C(18) using an acetonitrile:water gradient program as mobile phase. Injection of samples in 0.1 mol L(-1) H(3)PO(4)/KH(2)PO(4) buffer solution (pH 3) improved the chromatographic separation between the most polar components of matrix and the 6-chloronicotinic acid. Matrix components were removed to waste using an on-line clean-up method previously to post-column reaction. Limits of quantification were 0.3 and 5.0 microg L(-1) (corresponding to 1.2 and 20.0 microg kg(-1) in the honeybee sample) for imidacloprid and 6-chloronicotinic acid, respectively. The recovery was ranged from 80.2 to 91.7% with a relative standard deviation lower than 9.0%.

Flow injection analysis of imidacloprid in natural waters and agricultural matrixes by photochemical dissociation, chemical reduction, and nitric oxide chemiluminescence detection

A flow injection analysis (FIA) to quantify imidacloprid was developed based upon (1) ultraviolet (254 nm) photochemical dissociation of imidacloprid to produce nitrite, (2) chemical reduction of the nitrite to nitric oxide by iodide in acid, (3) removal of gas-phase nitric oxide from the aqueous stream using a membrane separator, and (4) detection of the nitric oxide by chemiluminescent reaction with ozone. The cross-reactivity of imidacloprid with eight metabolites of imidacloprid was determined using a commercial ELISA kit and the FIA method. While the ELISA kit demonstrated varying degrees of cross-reactivity, cross-reactivity in the FIA method was observed for only the N-nitro and N-nitroso metabolites. The optimized analytical FIA method, FIA provides a linear response in imidacloprid concentration over four orders of magnitude, has a limit of detection of 5.6 pmol (1.5 ng) of imidacloprid, and exhibits an inter-day precision of 0.4%. Spike-recoveries by FIA demonstrated excellent recovery of imidacloprid in natural waters, hemlock xylem fluid, honey, and grapes with little to no interference from the matrix.

Comparative study of sample preparation procedures to determine fipronil in pollen by gas chromatography with mass spectrometric and electron-capture detection

Several sample preparation methods have been assayed to analyze residues of fipronil in pollen at trace concentrations. Extraction with organic solvents, solid-phase extraction on either commercial cartridges or a Florisil-packed column and a matrix solid-phase dispersion, also with Florisil as a dispersing agent, have been tested. Determination of fipronil in the extracts has been carried out by GC with electron-capture and mass spectrometric detection. An extraction with acetonitrile followed by a clean-up on ODS or polymeric cartridges was the most suitable procedure to obtain acceptable recoveries and relatively simple chromatograms. The matrix-effects observed in the quantification can be corrected with a matrix-matched calibration.

Sensitive determination of thiamethoxam, imidacloprid and acetamiprid in environmental water samples with solid-phase extraction packed with multiwalled carbon nanotubes prior to high-performance liquid chromatography

This paper describes a novel method for sensitive determination of thiamethoxam, imidacloprid and acetamiprid based on solid-phase extraction with multiwalled carbon nanotubes as the packed materials. Factors that maybe influence the enrichment efficiency, such as sample flow rate, sample pH, and sample volume, were investigated in detail. Under the optimized conditions, the detection limits of thiamethoxam, imidacloprid and acetamiprid were 6.1, 5.4 and 6.7 ng L(-1), respectively. The experimental results indicated that there was good linearity (R2>0.9993) over the range of 0.08 approximately 100 ng mL(-1) and good reproducibility with the relative standard deviations over the range of 0.7 approximately 1.1% (n=6). The proposed method has been applied to the analysis of real-world water samples, and satisfactory achievements were obtained. The average spiked recoveries were in the range of 87.5 approximately 109.8%. All the results indicated that the proposed method could be used for the simultaneous determination of the three pesticides in environmental water samples at trace levels.