Xiaohuan Zang

Graphene-based solid-phase extraction combined with flame atomic absorption spectrometry for a sensitive determination of trace amounts of lead in environmental water and vegetable samples

Graphene, a novel class of carbon nanostructures, has great promise for use as sorbent materials because of its ultrahigh specific surface area. A new method using a column packed with graphene as sorbent was developed for the preconcentration of trace amounts of lead (Pb) using dithizone as chelating reagent prior to its determination by flame atomic absorption spectrometry. Some effective parameters on the extraction and complex formation were selected and optimized. Under optimum conditions, the calibration graph was linear in the concentration range of 10.0-600.0 μg L(-1) with a detection limit of 0.61 μg L(-1). The relative standard deviation for ten replicate measurements of 20.0 and 400.0 μg L(-1) of Pb were 3.56 and 3.25%, respectively. Comparative studies showed that graphene is superior to other adsorbents including C18 silica, graphitic carbon, and single- and multi-walled carbon nanotubes for the extraction of Pb. The proposed method was successfully applied in the analysis of environmental water and vegetable samples. Good spiked recoveries over the range of 95.3-100.4% were obtained. This work not only proposes a useful method for sample preconcentration, but also reveals the great potential of graphene as an excellent sorbent material in analytical processes.

Dispersive liquid–liquid microextraction combined with high performance liquid chromatography–fluorescence detection for the determination of carbendazim and thiabendazole in environmental samples

A rapid and sensitive method for the determination of carbendazim (methyl benzimidazole-2-ylcarbamate, MBC) and thiabendazole (TBZ) in water and soil samples was developed by using dispersive liquid-liquid microextraction (DLLME) coupled with high performance liquid chromatography with fluorescence detection. The water samples were directly used for the DLLME extraction. For soil samples, the target analytes were first extracted by 0.1 mol L(-1) HCl. Then, the pH of the extract was adjusted to 7.0 with 2 mol L(-1) NaOH before the DLLME extraction. In the DLLME extraction method, chloroform (CHCl(3)) was used as extraction solvent and tetrahydrofuran (THF) as dispersive solvent. Under the optimum conditions, the enrichment factors for MBC and TBZ were ranged between 149 and 210, and the extraction recoveries were between 50.8 and 70.9%, respectively. The linearity of the method was obtained in the range of 5-800 ng mL(-1) for water sample analysis, and 10-1000 ng g(-1) for soil samples, respectively. The correlation coefficients (r) ranged from 0.9987 to 0.9997. The limits of detection were 0.5-1.0 ng mL(-1) for water samples, and 1.0-1.6 ng g(-1) for soil samples. The relative standard deviations (RSDs) varied from 3.5 to 6.8% (n=5). The recoveries of the method for MBC and TBZ from water samples at spiking levels of 5 and 20 ng mL(-1) were 84.0-94.0% and 86.0-92.5%, respectively. The recoveries for soil samples at spiking levels of 10 and 100 ng g(-1) varied between 82.0 and 93.4%.

Metal–Organic Framework Derived Magnetic Nanoporous Carbon: Novel Adsorbent for Magnetic Solid-Phase Extraction

The fabrication of a magnetic nanoporous carbon (MNPC) via one-step direct carbonization of Co-based metal-organic framework has been achieved without using any additional carbon precursors. The morphology, structure, and magnetic behavior of the as-prepared Co-MNPC were characterized by using the techniques of scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, Raman spectroscopy, N2 adsorption, and vibrating sample magnetometer. The Co-MNPC has a high specific surface area, large pore volume, and super paramagnetism. Its performance was evaluated by the magnetic solid-phase extraction of some neonicotinoid insecticides from water and fatmelon samples followed by high-performance liquid chromatographic analysis. The effects of the main experimental parameters that could affect the extraction efficiencies were investigated. The results demonstrated that the Co-MNPC had an excellent adsorption capability for the compounds.

The use of graphene‐based magnetic nanoparticles as adsorbent for the extraction of triazole fungicides from environmental water

A graphene-based magnetic nanocomposite (graphene-ferriferrous oxide; G-Fe(3)O(4)) was synthesized and used as an effective adsorbent for the preconcentration of some triazole fungicides (myclobutanil, tebuconazole, and hexaconazole) in environmental water samples prior to high-performance liquid chromatography-ultraviolet detection. The method, which takes the advantages of both nanoparticle adsorption and magnetic phase separation from the sample solution, could avoid the time-consuming experimental procedures commonly involved in the traditional solid phase extraction such as centrifugation and filtrations. Various experimental parameters affecting the extraction efficiencies such as the amount of the magnetic nanocomposite, extraction time, the pH values of the sample solution, salt concentration, and desorption conditions were investigated. Under the optimum conditions, the enrichment factors of the method for the three analytes were 5824, 3600, and 4761, respectively. A good linearity was observed in the range of 0.1-50 ng/mL for tebuconazole and 0.05-50 ng/mL for myclobutanil and hexaconazole, respectively, with the correlation coefficients ranging from 0.9992 to 0.9996. The limits of detection (S/N = 3) of the method were between 0.005 and 0.01 ng/mL. The results indicated that as a magnetic solid-phase extraction adsorbent, the graphene-ferriferrous oxide (G-Fe(3)O(4)) has a great potential for the preconcentration of some compounds from liquid samples.

Polydimethylsiloxane/metal-organic frameworks coated fiber for solid-phase microextraction of polycyclic aromatic hydrocarbons in river and lake water samples.

In this study, polydimethylsiloxane/metal-organic frameworks (PDMS/MOFs), including PDMS/MIL-101 and PDMS/MOF-199, were immobilized onto a stainless steel wire through sol-gel technique as solid-phase microextraction (SPME) fiber coating. The prepared fibers were used for the extraction of some polycyclic aromatic hydrocarbons (PAHs) from water samples prior to gas chromatography-mass spectrometry (GC-MS) analysis. Under the optimized experiment conditions, the PDMS/MIL-101 coated fiber exhibited higher extraction efficiency towards PAHs than that of PDMS/MOF-199. Several parameters affecting the extraction of PAHs by SPME with PDMS/MIL-101 fiber, including the extraction temperature, extraction time, sample volume, salt addition and desorption conditions, were investigated. The limits of detection (LODs) were less than 4.0 ng L(-1) and the linearity was observed in the range from 0.01 to 2.0 µg L(-1) with the correlation coefficients (r) ranging from 0.9940 to 0.9986. The recoveries of the method for the PAHs from water samples at spiking levels of 0.05 and 0.2 µg L(-1) ranged from 78.2% to 110.3%. Single fiber repeatability and fiber-to-fiber reproducibility were less than 9.3% and 13.8%, respectively.

Graphene-based Magnetic Solid Phase Extraction-Dispersive Liquid Liquid Microextraction Combined with Gas Chromatographic Method for Determination of Five Acetanilide Herbicides in Water and Green Tea Samples

Abstract A novel analytical method was developed for the extraction and determination of five chloroacetanilide herbicides (alachlor, acetochlor, metolachlor, butachlor and pretilachlor) in water and green tea samples by graphene-based magnetic solid phase extraction and dispersive liquid-liquid microextraction followed by gas chromatography-flame ionization detection (GC-FID). Some important experimental parameters that could influence the extraction efficiency were investigated. Under the optimum conditions, as high as 3399 to 4002 fold enrichment factors for the herbicides were achieved. A good linearity was obtained in the range of 0.1–50.0 μg L−1 for all the five herbicides with the correlation coefficients (r) varying from 0.9973 to 0.9993. The limits of detection ranged from 0.01 to 0.03μg L−1. The method was applied to the analysis of the chloroacetanilide herbicides in environmental water and green tea samples with a satisfactory result. The recoveries of the method for the analytes were in the range from 80.2% to 105.3%, and the relative standard deviations were between 3.8% and 5.8%.

The use of silica‐coated magnetic graphene microspheres as the adsorbent for the extraction of pyrethroid pesticides from orange and lettuce samples followed by GC–MS analysis

Graphene-grafted ferroferric oxide microspheres were used as the adsorbent to extract some pyrethroid pesticides (bifenthrin, λ-cyhalothrin, cyfluthrin, cypermethrin, fenvalerate, and deltamethrin) from orange and lettuce samples prior to their determination by GC-MS. The main variables that could affect the extraction, including the amount of the adsorbent, pH of the sample solution, extraction time, concentration of salt, and desorption conditions, were investigated and optimized. Under the optimized conditions, a linear response was obtained in the concentration range of 0.3-100.0 ng/g for the analytes with the coefficients of determination ranging from 0.9877 to 0.9925. The LODs for the pyrethroids ranged from 0.01 to 0.02 ng/g. The method provided a good repeatability with RSDs < 10.6%. The recoveries for the six pyrethroid pesticides were in the range from 90.0 to 103.7%. The method was applied to the determination of the pesticides in orange and lettuce samples with a satisfactory result.

A Green and Efficient Synthesis of 9-Aryl-3,4,5,6,7,9-hexahydroxanthene-1,8-dione using a Task-Specific Ionic Liquid as Dual Catalyst and Solvent

A green and efficient method for the preparation of 9-aryl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-dione has been developed using functionalized ionic liquids as a catalyst and a reaction medium. The nature of both the counter anion and cation influence the catalytic performance of the ionic liquids. The ionic liquid can be recycled and reused without apparently loss of activity.

Developments in Liquid-phase Microextraction Method Based on Solidification of Floating Organic Drop

Abstract The liquid-phase microextraction based on solidification of floating organic drop (LPME-SFO), which incorporated sampling, extraction, and concentration into a single step, has been developed to be a new environmentally benign sample-preparation technique. This novel technique has proved to be low-cost and virtually organic solvent-free and could provide a high enrichment factor. It can be easily integrated with gas chromatography (GC), high-performance liquid chromatography (HPLC), and atomic absorption spectrometry (AAS). The basic principles and the main parameters that affect the extraction efficiency and recent applications of the LPME-SFO are briefly reviewed in this paper.

1‐n‐Butyl‐3‐Methylimmidazolium Tetrafluoroborate–Promoted Green Synthesis of 5‐Arylidene Barbituric Acids and Thiobarbituric Acid Derivatives

Abstract The room temperature ionic liquid 1‐n‐butyl‐3‐methylimmidazolium tetrafluoroborate ([bmim]BF4) was used to promote the synthesis of 5‐arylidene barbituric acids and thiobarbituric acid derivatives under the solid‐state conditions of grinding or microwave irradiation without organic solvent. The yields were 77.9–96.2%. It is shown that the proposed method is fast, efficient, and environmentally benign.