Jing-Jun Ma

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.

Application of graphene as a sorbent for preconcentration and determination of trace amounts of chromium(III) in water samples by flame atomic absorption spectrometry

Graphene, a novel class of carbon nanostructure, has great promise for use as a sorbent material because of its ultrahigh specific surface area. A new method using a column packed with graphene as sorbent is developed for the preconcentration of trace amounts of chromium(III) prior to its determination by flame atomic absorption spectrometry. Some effective parameters on the extraction and complex formation were selected and optimized. The optimum experimental conditions of the proposed method were: pH, 8.0; amount of chelating agent, 2.0 mL of 0.1 mol L−1 8-hydroxyquinoline solution; eluent type and its volume, 2.0 mL of 2.0 mol L−1 nitric acid; flow rates of sample and eluent solution, 2.0 mL min−1. Under optimum conditions, an enrichment factor of 125 was obtained. The calibration graph was linear in the concentration range of 10.0–1000.0 μg L−1 with a correlation coefficient of 0.9995. The detection and quantification limits were 0.5 and 1.6 μg L−1, respectively. The relative standard deviation for ten replicate measurements were 4.3% for 20.0 μg L−1 and 3.4% for 800.0 μg L−1 of Cr(III). The proposed method was applied to tap water, sea water, and river water, and its accuracy was assessed through the analysis of certified reference water and recovery experiments. The recoveries of spiked samples were in the range of 95.7–101.2%.

Ultrasound-assisted emulsification solidified floating organic drop microextraction for the determination of trace cadmium in water samples by flame atomic absorption spectrometry

A liquid-phase microextraction technique was developed using ultrasound-assisted emulsification solidified floating organic drop microextraction (USAE-SFODME) combined with flame atomic absorption spectrometry (FAAS) for the extraction and determination of trace cadmium in water samples. Microextraction efficiency factors, such as extraction solvent type and extraction volume, time, temperature, pH, the amount of the chelating agent, and salt effect, were investigated and optimized. Under optimum conditions, an enrichment factor of 81.0 was obtained for 6.0 mL of water sample. The calibration graph was linear in the range of 10-450 mg L-1 with a detection limit of 0.66 µg L-1. The relative standard deviations (RSD) for ten replicate measurements of 20 and 300 µg L-1 of Cd were 3.34% and 2.42%, respectively. The accuracy of the proposed method was assessed either by determination of Cd in a certified reference material of water or by addition-recovery experiments

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.

NbCl5 as an Efficient Catalyst for Chemoselective Synthesis of 1,1-Diacetates Under Solvent-Free Conditions

Abstract A mild and efficient method for the chemoselective preparation of 1,1-diacetates catalyzed by NbCl5(5 mmol%) under solvent-free conditions has been developed. The yields are in the range of 93–98%. This protocol offered several advantages, including low catalyst loading, good yields, short reaction times, and environmentally friendliness.

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.

NbCl5 as an Efficient Catalyst for the Synthesis of 1,5-Benzodiazepine Derivatives

Abstract 1,5-Benzodiazepine derivatives were synthesized in moderate to excellent isolated yields by the condensation reactions of o-phenylenediamine and ketones catalyzed by NbCl5 under mild conditions using n-hexane as solvent at 50°C. This method is simple and effective with good yields.

NbCl5-Catalyzed, Solvent-Free, One-Pot Synthesis of Coumarins

Abstract NbCl5 is found to be an efficient catalyst for the Pechmann condensation reaction of phenols and β-keto ester leading to the formation of coumarin derivatives in excellent yields under solvent-free conditions. The reaction protocol is simple and environmentally friendly.

N′-(5-Bromo-2-hy­droxy­benzyl­idene)-4-nitro­benzohydrazide methanol monosolvate

In the title compound, C14H10BrN3O4·CH4O, the benzohydrazide molecule is nearly planar [maximum deviation = 0.110 (2) Å]. The mean planes of the two benzene rings make a dihedral angle of 8.4 (3)°. In the benzohydrazide molecule, there is an intramolecular O—H⋯N hydrogen bond and the NH group is hydrogen bonded to the methanol solvent molecule. In the crystal, intermolecular O—H⋯O hydrogen bonds involving the methanol solvent molecule link the benzohydrazide molecules to form chains which propagate along the a axis.

Study of the Interaction of Fangchinoline with Human Serum Albumin by Fluorescence and UV Spectroscopic Method

Abstract The interaction of fangchinoline with human serum albumin (HSA) was studied by use of fluorescence quenching spectra, synchronous fluorescence spectra, and ultraviolet spectra. It was shown that fangchinoline has a strong ability to quench the fluorescence of HSA. The Stern‐Volmer curves based on the quenching of the fluorescence of HSA by fangchinoline indicated that the quenching mechanism of fangchinoline on HSA was static quenching and non‐radiation energy transfer. Based on the Förster theory of non‐radiation energy transfer, the binding distances (r) and the binding constants (K A) between fangchinoline and HSA were found. The thermodynamic parameters obtained revealed that the interaction between fangchinoline and HSA was mainly driven by hydrophobic force. The conformational changes of HSA were investigated by use of synchronous fluorescence. The result indicates that an ionic electrostatic interaction between fangchinoline and HSA could not be excluded.