Aijun Dong

Multi-residue method for determination of seven neonicotinoid insecticides in grains using dispersive solid-phase extraction and dispersive liquid–liquid micro-extraction by high performance liquid chromatography

A method using dispersive solid-phase extraction and dispersive liquid-liquid micro-extraction cleanup followed by high performance liquid chromatography (HPLC) has been established for determination of seven neonicotinoid insecticides residues in grains including brown rice, maize, millet and oat. Based on an appraisal of the characteristics of HPLC, validation experiments were conducted for seven neonicotinoid insecticides. In the method, dispersive solid-phase extraction was carried out using PSA and bonded C18 coupled with graphitised carbon black with acetonitrile as the eluted solvent. In the linear range of each pesticide, the correlation coefficient was R(2) ≥ 0.99. At the low, medium and high three fortification levels of 0.05-0.8 mg kg(-1), recoveries fell within 76-123%. The relative standard deviation was between 0.9% and 12.6% for seven neonicotinoid pesticides. Low limits of detection (0.002-0.005 mg kg(-1)) and quantification (0.007-0.018 mg kg(-1)) were readily achieved with this method for all tested pesticides.

Multiresidue method for determination of 88 pesticides in berry fruits using solid-phase extraction and gas chromatography–mass spectrometry: Determination of 88 pesticides in berries using SPE and GC–MS

A method using solid phase extraction (SPE) cleanup followed by gas chromatography-mass spectrometry (GC-MS) has been established for quantitative determination of 88 pesticide residues in berry fruits including raspberry, strawberry, blueberry and grape. Based on an appraisal of the characteristics of GC-MS, validation experiments were conducted for 88 pesticides. In the method, solid-phase extraction was carried out using Envi-Carb cartridge coupled with NH(2)-LC cartridge with acetonitrile-toluene (3:1, v/v) as the eluted solvent. In the linear range of each pesticide, the correlation coefficient was R(2)⩾0.99. At the low, medium and high three fortification levels of 0.05-0.5mgkg(-1), recoveries fell within 63-137%. The relative standard deviation was between 1% and 19% for all 88 pesticides. Low limits of detection (0.006-0.05mgkg(-1)) and quantification (0.02-0.15mgkg(-1)) were readily achieved with this method for all tested pesticides.

Determination of free amino acids and 18 elements in freeze-dried strawberry and blueberry fruit using an Amino Acid Analyzer and ICP-MS with micro-wave digestion

The objective of this study was to investigate the level of 18 trace elements of two freeze-dried samples from the Blueberry (Vaccinium corymbosum) and the Strawberry (Fragaria × Ananassa). The total free amino acid composition in the blueberry and strawberry was determined by an Amino Acid Analyzer. Eleven free amino acids were found in both berries. The trace elements in each dried fruit sample were determined by ICP-MS with microwave digestion. The linearity range of the standard curves was 0-1250.0 μg L(-1) (Mg, P, K, Ca),while in all cases, except for B, Na, Al, Cr, Mn, Fe, Ni, Cu, Zn, Se, Cd, Pb, Ge and As, which was 125.0 μg mL(-1), all related coefficients were above 0.9999; recovery was in the range of 79.0-106.8%. Minor concentrations of nutritional elements were found in each freeze-dried berry. In sum, the toxic trace element analysis found the content of toxic trace elements in each freeze-dried berry sample was safe for human consumption and that the overall quality of the blueberry surpassed that of the strawberry. The results certify that the two freeze-dried berries have potential for human consumption in value-added products and have a certain theoretical and practical significance.

Effect of pesticide 1-[6-chloro-3-methyl-pyridyl-8-nitro-7-methyl-1 2 3 5 6 7-hexahydro imidazo (1,2a)]-pyridine when responding to a wheat plant's antioxidant defense system.

The purpose of this research was to establish an analytical method for analysing the 1-[6-chloro-3-methyl-pyridyl-8-nitro-7-methyl-1 2 3 5 6 7-hexahydro imidazo-(1,2a)]-pyridine (IPP) residue levels and to evaluate the difference in plant growth and its physical condition. A high performance liquid chromatography connected to a diode array detector (HPLC-DAD) was also employed. The results showed that the content of protein and water soluble carbohydrate (WSC) treated by IPP were initially higher with a significant delayed decrease. The biomarker response showed, even at a lower dose rate, exposure to the IPP caused stress effects and modified the activity of superoxide dismutase (SOD), guaiacol peroxidase (POD), catalase (CAT) and polyphenol oxidase (PPO). Different patterns of biomarker responses were observed by an increase in SOD and malondialdehyde (MDA), and differential effects for antioxidant enzymes with a decrease in CAT, POD and PPO. The conclusions show that this profile of biomarker variation could represent a useful method to characterise exposure to IPP in a wheat plant.

Preparation and characterization of surface molecularly imprinted film coated on a magnetic nanocore for the fast and selective recognition of the new neonicotinoid insecticide paichongding (IPP)

In this work, we present a general method to prepare surface molecularly imprinted film on a magnetic nanocore for new neonicotinoid insecticide paichongding (IPP) recognition. First, magnetic Fe3O4 nanoparticles were synthesized by a hydrothermal method and coated with SiO2 on the surface, then were vinyl-modified to be Fe3O4@SiO2@CC which was the magnetic core. After that, magnetic molecularly imprinted nanoparticles (MMIPs) were synthesized by surface-imprinted polymerization in airtight tubes at 60 °C for 24 h, using IPP as the template, methacrylic acid as the functional monomer and ethylene glycol dimethacrylate as cross-linkers. The resulting IPP-MMIPs possess specific recognition ability, fast adsorption kinetics, high adsorption capacity, and can be easily collected under an external magnetic field. The IPP-MMIPs were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and vibrating sample magnetometry (VSM). The binding experiments showed a relatively high adsorption capacity (17.30 mg g−1) and specific recognition ability over structurally related compounds. Therefore, IPP-MMIPs have the potential to become a sensitive and selective approach for IPP recognition and separation.

Analysis of the Essential Oils of Pine Cones of Pinus koraiensis Steb. Et Zucc. and P. sylvestris L. from China

Abstract The chemical composition of the essential oil obtained from pine cones of Pinus koraiensis and Pinus sylvestris from northeast China was analyzed by gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS), and 35 and 31 components were identified, respectively. α-pinene (35.2%), limonene (18.4%), β-pinene (8.7%), β-caryophyllene (3.5%) and myrcene (3.0%) were the main components in P. koraiensis cone oil. Aromadendrene (20.2%), α-pinene (18.5%), α-longipinene (10.5%) and α-terpineol (5.5%) were the main components in P. sylvestris cone oil. The antioxidant activity of the oils from P. koraiensis and P. sylvestris was evaluated using the DPPH.

Diterpenoid acids from Pinus koraiensis

Two new diterpenoid acids, pinusenocarp (1) and pinusenoid (2), were isolated from the pine cone of Pinus koraiensis. All the compounds were characterized on the basis of spectral analysis, viz. 1H NMR, 13C NMR, IR, UV, ESI-MS, and elemental analysis.

Application of β-cyclodextrin–reduced graphene oxide nanosheets for enhanced electrochemical sensing of the nitenpyram residue in real samples

A sensitive, simple and cost-effective method for large-scale monitoring of nitenpyram (NIT) is important in food quality control. This study presents a new approach for the rapid detection of NIT using a glassy carbon electrode modified by β-cyclodextrin–reduced graphene oxide nanosheets, which exhibits a considerable improvement of the reduction peak current of NIT. After incubation at 0 °C for 8 min, the resulting electrochemical platform presented high sensitivity with a wide linear range from 5 × 10−7 M to 2.2 × 10−5 M as well as a low detection limit of 1.1 × 10−7 M by linear sweep voltammetry. In addition, water-extraction followed by liquid–liquid extraction pretreatment has been developed to improve the extraction rate and efficiently eliminate the interferent. This method has been applied for the determination of spiked NIT in three kinds of rice samples with the detection limit of 0.3 mg kg−1. The recovery was 74.56–107.15% and the results were validated through HPLC.

Water-compatible surface imprinting of 'Saccharin sodium' on silica surface for selective recognition and detection in aqueous solution.

In this work, a saccharin sodium imprinted nanoparticles composite material has been successfully synthesized in aqueous solution. This molecular imprinted material has promising practical utility in the detection of saccharin sodium. First, we synthesized SiO2 nanoparticles, followed by the modification of functional amino group. Then we used functionalized SiO2@NH2 as the cores, saccharin sodium as the template, acrylic acid (AA) as the functional monomer and ammonium persulphate (APS) as the initiator. Molecularly imprinted nanoparticles (MIPs) were synthesized by surface-imprinted polymerization under airtight tubes at 60 °C for 12 h. MIPs were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and thermal gravimetric analysis (TGA). The binding experiments were shown to have relatively high adsorption capacity (8.965 mg g(-1)) and selective recognition ability over structurally related compounds. Therefore, MIPs provide a sensitive and selective approach and offer the potential to become a new key for the detection of saccharin sodium.

A facile molecularly imprinted electrochemical sensor based on graphene: application to the selective determination of thiamethoxam in grain

In this study, we report a facile method for the preparation of molecularly imprinted polymer based graphene for the electrochemical detection of thiamethoxam residue. We choose p-vinylbenzoic acid as a functional monomer; it can be used to add recognition units and alkenyl units onto the surface of graphene via π–π interactions in just one step, effectively simplifying the reaction process. And an ultra-thin imprinting film (2 nm) is formed by reducing the addition step involving the alkenyl modifier. Due to the irreversible electrochemical reduction characteristics of thiamethoxam, the template can be removed easily using cyclic voltammetry scanning, without the need for organic solvents. The performance of the fabricated sensor was evaluated and the results indicated that the sensor exhibited excellent specific recognition abilities for thiamethoxam detection; the imprinting factor is 2.36. The peak current from thiamethoxam is linearly proportional to its concentration over the range from 0.5 to 20 μM, and the detection limit is 0.04 μM. The practical application of the sensor was also realized in the selective detection of thiamethoxam in real samples.