Xiaodong Huang

Metal–organic framework preparation using magnetic graphene oxide–β-cyclodextrin for neonicotinoid pesticide adsorption and removal

A novel magnetic copper-based metal-organic framework (M-MOF) was prepared using a Fe4O3-graphene oxide (GO)-β-cyclodextrin (β-CD) nanocomposite as the magnetic core and support, and used for adsorption and removal of neonicotinoid insecticide pollutants from aqueous solution. M-MOF characterization suggested that 1Fe4O3-GO-β-CD consisted of a thin single layer with anchored Fe3O4. The M-MOF was coated on the Fe4O3-GO-β-CD surface. The M-MOF had a large Brunauer-Emmett-Teller surface area (250.33m2g-1) and high super-paramagnetism with saturation magnetization of 10.47emug-1. Adsorption model analysis showed that the equilibrium data for thiacloprid fitted Langmuir monolayer adsorption and the other insecticides tested showed Freundlich bimolecular layer adsorption. The results show that M-MOF is a promising hybrid adsorbent for rapid removal of neonicotinoid insecticide pollutants from environmental waters.

Visual and Colorimetric Sensing of Metsulfuron-Methyl by Exploiting Hydrogen Bond-Induced Anti-Aggregation of Gold Nanoparticles in the Presence of Melamine

Various highly sensitive and selective analytical methods have been used to monitor metsulfuron-methyl residue in the environment. However, these methods involve costly instruments and complex, time-consuming operations performed in laboratories. Here, a rapid, convenient, and sensitive colorimetric sensor based on anti-aggregation of gold nanoparticles (AuNPs) is demonstrated for the rapid detection of metsulfuron-methyl in agricultural irrigation water. The AuNPs could be induced to aggregate in the presence of melamine and exhibited a distinct color change from wine-red to blue. The aggregation was suppressed by a strong hydrogen-bonding interaction between metsulfuron-methyl and melamine. The differences of the absorbance at 523 nm (ΔA523) and the color change was linearly related to metsulfuron-methyl concentration over the range 0.1–100 mg/L, as observed visually and by UV-vis (Ultraviolet-visible) spectrometry. The detection limit of the sensor was as low as 0.05 mg/L (signal/noise = 3), and was used to determine metsulfuron-methyl in spiked water and in agricultural irrigation water samples. Recoveries were in the range of 71.2–100.4%, suggesting that the colorimetric sensor was suitable for the determination of metsulfuron-methyl in agricultural water samples.

Preparation of a magnetic multiwalled carbon nanotube@polydopamine/zeolitic imidazolate framework-8 composite for magnetic solid-phase extraction of triazole fungicides from environmental water samples

A novel magnetic zinc-based zeolitic imidazolate framework (MMP/ZIF-8) has been prepared using a magnetic multiwalled carbon nanotube@polydopamine nanocomposite as the magnetic core and support. It was then used as an adsorbent for magnetic solid-phase extraction of triazole fungicides from environmental water samples. Successful synthesis of MMP/ZIF-8 was confirmed by material characterization, and the results showed that the synthetic composite has a high Brunauer–Emmett–Teller surface area (141.56 m2 g−1), large total pore volume (0.636 mL g−1), and high superparamagnetism with a saturation magnetization of 44.1 emu g−1. To evaluate the extraction performance of MMP/ZIF-8, the main parameters that affect the extraction efficiency were optimized. Under the optimal conditions, the developed method shows good linearity (R2 ≥ 0.9915) in the concentration range 1–400 μg L−1. Low limits of detection (0.08–0.27 μg L−1, signal/noise = 3 : 1) and good precision (intraday relative standard deviation ≤ 7.73%, interday relative standard deviation ≤ 9.65%) are also achieved. The developed method was applied for analysis of triazole fungicides in environmental water samples.

Ionic liquid-modified luffa sponge fibers for dispersive solid-phase extraction of benzoylurea insecticides from water and tea beverage samples

In the present study, a convenient, low-cost, sensitive and environmentally friendly method for the determination of four benzoylurea insecticides (BUs) in water and tea beverage samples was developed. The alkalized luffa sponge fibers (AL) were modified by the ionic liquid 1-hexadecyl-3-methylimidazolium bromide ([C16MIM]Br) through physisorption and used as the sorbent of dispersive solid-phase extraction (DSPE). The sorbent was characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The retained analytes were eluted using 200 μL of methanol and then quantified by high performance liquid chromatography-ultraviolet detection (HPLC-UVD). The influences of extraction parameters of [C16MIM]Br-AL-DSPE on the BUs were thoroughly studied. Under the optimal conditions, good linearity was observed over the concentration range of 1–500 ng mL−1, with coefficients of determination greater than 0.99. The limits of detection (LODs) of the developed method were 0.14–0.21 ng mL−1 in water and 0.19–0.23 ng mL−1 in tea beverage samples. Satisfactory recoveries were achieved in the range of 72.8–89.3%, with relative standard deviations lower than 10%. Finally, the established [C16MIM]Br-AL-DSPE-HPLC-UVD method was successfully applied for the determination of BU residues in environmental water and tea beverage samples.

Dispersive micro-solid-phase extraction of benzoylurea insecticides in water samples with hyperbranched polyester composite as sorbent

A pretreatment method using hyperbranched polyester (HBPE) composite as sorbent based on dispersive micro-solid-phase (d-μ-SPE) extraction preceding high-performance liquid chromatography analysis was developed for the determination of benzoylurea insecticides (BUs) in water samples. Parameters that may influence the extraction efficiency, such as the diameter and the amount of the sorbent, extraction and desorption time and the pH value of the solution, were investigated and optimized using batch and column procedures. Under optimized conditions, good linearity was obtained for all of the tested compounds, with r values of at least 0.9924. The linearity of the method was determined in the range of 1–25 000 μg L−1. The limits of detection (LODs) ranged from 0.024 to 0.068 μg L−1. The recoveries of the four benzoylurea insecticides in water samples increased from 85.50–96.12%. The results confirmed the possibility of using hyperbranched polyester in the determination of relatively hydrophobic trace pesticides residues. Finally, the proposed method was applied to the determination of BUs in water samples with satisfactory results.

Anti-Agglomeration Behavior and Sensing Assay of Chlorsulfuron Based on Acetamiprid-Gold Nanoparticles

Monitoring of low levels of chlorsulfuron in environmental water samples is important. Although several detection methods have been developed, they all have some drawbacks, such as being time-consuming, requiring expensive instruments and experienced operators, and consuming large volumes of organic solvents. There is an urgent need for a simple, rapid, and inexpensive detection method for chlorsulfuron. Herein, such a method was developed using anti-aggregation of gold nanoparticles (AuNPs) in the presence of acetamiprid in agricultural irrigation water samples. Aggregation of the AuNPs was induced by acetamiprid, and this produced a distinct color change from Bordeaux red to blue. However, the strong hydrogen bonding interaction between chlorsulfuron and acetamiprid could inhibit AuNP aggregation. The effect of chlorsulfuron on the anti-agglomeration behavior of AuNPs was monitored by ultraviolet–visiblespectroscopy (UV-Vis) and the naked eye over a concentration range 0.1–100 mg/L. The detection limit for chlorsulfuron was 0.025 mg/L (signal-to-noise ratio of three). This colorimetric method was successfully applied to the determination of chlorsulfuron in spiked tap water and agricultural irrigation water with satisfactory recoveries (76.3%–94.2%).

Adsorption and removal of organophosphorus pesticides from environmental water and soil samples by using magnetic multi-walled carbon nanotubes @ organic framework ZIF-8

In this study, the functional adsorbent metal–organic framework ZIF-8/magnetic multi-walled carbon nanotubes (M-M-ZIF-8) was successfully prepared for removal of eight organophosphorus pesticides from environmental water and soil samples. The M-M-ZIF-8 was characterized and their adsorption capacity was evaluated based on their isothermal adsorption curves. The results suggest that ZIF-8 particles are deposited on the surface of the magnetic MWCNTs via coordination–polymerization strategy. In addition, M-M-ZIF-8 has high static adsorption capacities for organophosphorus pesticides because of its high specific surface area and porous structure. The static adsorption data fit the Freundlich adsorption model better than the Langmuir model. Under the optimized conditions, M-M-ZIF-8 was successfully applied to remove the eight organophosphorus pesticides from environmental water and soil samples. A possible mechanism is valence-electron-driven adsorption by sharing or exchanging of electrons between the organophosphorus pesticide molecules and the vacant active sites of M-M-ZIF-8. Therefore, M-M-ZIF-8 is a promising hybrid adsorbent for adsorption and removal of organic pollutions from the environment.

Survey of Four Groups of Cumulative Pesticide Residues in 12 Vegetables in 15 Provinces in China

The present study investigated the concentrations of residues of four groups of pesticides in the Peoples Republic of China: organophosphorus, carbamate, pyrethroid, and triazine pesticides. Twenty-six pesticides were examined using gas chromatography-tandem mass spectrometry and liquid chromatography-tandem mass spectrometry in 2,169 samples of 12 typical vegetables collected from 15 provinces in China. The results showed that 908 (41.9%) samples were positive, with 133 (6.1%) samples exceeding the limit legal in China. Leafy vegetables showed higher positive rates than fruits and root vegetables. Organophosphorus, carbamate, pyrethroid, and triazine pesticides were found in 11.8, 7.7, 13.9, and 10.9% of the samples, respectively, which provided important information on current concentrations of cumulative assessment group pesticide residues for vegetables in China. Of the positive samples, a slight violation rate of 1.9% for the organophosphorus pesticide category exceeded Chinas maximum residue limits. Positive rates for chlorpyrifos in celery, pak-choi, and leeks were higher, but fewer exceeded Chinas maximum residue limits.