Ruiyang Ma

Magnetic microsphere-confined graphene for the extraction of polycyclic aromatic hydrocarbons from environmental water samples coupled with high performance liquid chromatography–fluorescence analysis

In this paper, a magnetic microsphere-confined graphene adsorbent (Fe3O4@SiO2-G) was fabricated and used for the extraction of five polycyclic aromatic hydrocarbons (fluorene, anthracene, phenanthrene, fluoranthene and pyrene) from environmental water samples prior to high performance liquid chromatography with fluorescence detection. The Fe3O4@SiO2-G was characterized by various instrumental methods. Various experimental parameters that could affect the extraction efficiencies, such as the amount of Fe3O4@SiO2-G, the pH and ionic strength of sample solution, the extraction time and the desorption conditions, were investigated. Due to the high surface area and excellent adsorption capacity of the Fe3O4@SiO2-G, satisfactory extraction can be achieved with only 15mg of the adsorbent per 250mL solution and 5min extraction. Under the optimum conditions, a linear response was observed in the concentration range of 5-1500ngL(-1) for fluorene, 2.5-1500ngL(-1) for anthracene and 15-1500ngL(-1) for phenanthrene, fluoranthene and pyrene, with the correlation coefficients (r) ranging from 0.9897 to 0.9961. The limits of detection (S/N=3) of the method were between 0.5 and 5.0ngL(-1). The relative standard deviations (RSDs) were less than 5.6%. The recoveries of the method were in the range between 83.2% and 108.2%. The results indicated that this graphene-based magnetic nanocomposite had a great adsorptive ability toward the five polycyclic aromatic hydrocarbons from environmental water samples.

Fabrication of magnetic microsphere-confined graphene for the preconcentration of some phthalate esters from environmental water and soybean milk samples followed by their determination by HPLC.

In this study, a magnetic microsphere-confined graphene (Fe3O4@SiO2-G) was prepared as a novel adsorbent for the preconcentration of some phthalate esters in environmental water and soybean milk samples prior to high performance liquid chromatography analysis. The properties and morphology of the Fe3O4@SiO2-G were characterized by transmission electron microscopy and X-ray diffraction. This novel graphene-based magnetic nanocomposite showed great adsorptive ability toward the analytes. The method, which takes the advantages of both the high adsorption capacity of G and easy phase separation of the magnetic adsorbent from the sample solution, could avoid the time-consuming experimental procedures related to the traditional solid phase extraction. Various experimental parameters that could affect the extraction efficiencies, such as the amount of Fe3O4@SiO2-G, the extraction time, the pH of sample solution and the desorption conditions, were investigated. Under the optimum conditions, the limits of detection (S/N=3) of the method for the compounds were between 0.07 and 0.10 ng mL(-1) in water samples, and between 0.15 and 0.30 ng mL(-1) in soybean milk samples. The relative standard deviations (RSDs) varied from 2.7% to 6.1% (n=5). The recoveries of the method were in the range between 87.2% and 109.0% for environmental water and soybean milk samples. The method is suitable to determine the five phthalate esters (diallyl phthalate, di-n-propyl-phthalate, benzyl butyl phthalate, dicyclohexyl-phthalate and diethyl-hexyl-phthalate) in environmental water and soybean milk samples.

A solid phase microextraction fiber coated with graphene–poly(ethylene glycol) composite for the extraction of volatile aromatic compounds from water samples

Poly(ethylene glycol)-grafted graphene (PEG-g-G) was prepared and used as the solid phase microextraction (SPME) fiber coating for the extraction of seven volatile aromatic compounds (VACs) from water samples followed by the determination with gas chromatography-flame ionization detection. The PEG-g-G coating was characterized by both the thermal gravimetric analysis and scanning electron microscopy. The results verified that the PEG was successfully grafted onto the surface of graphene and the coating had a highly porous structure. Several important experimental parameters that could influence the SPME efficiency were investigated and optimized. Under the optimized conditions, the limits of detection were in the range from 1.0 to 6.0 ng L(-1). The relative standard deviations for intraday and interday variations were in the range of 1.8-5.8% and 5.1-8.3%, and for fiber-to-fiber variations, were between 6.5 and 11.9%, respectively. The results indicated that the PEG-g-G fiber had the advantages of high extraction efficiency and good thermal stability and durability. It can be reused more than 200 times without a significant loss of extraction efficiency. The method was successfully applied to the analysis of seven VACs in tap, river and mineral water samples.

Magnetic porous carbon as an adsorbent for the enrichment of chlorophenols from water and peach juice samples

In this paper, porous carbon with a highly ordered structure was synthesized using zeolite ZSM-5 as a template and sucrose as a carbon source. Through the in situ reduction of Fe(3+), magnetic property was successfully introduced into the ordered porous carbon, resulting in a magnetic porous carbon (MPC). MPC was used as an adsorbent for the extraction of some chlorophenols (2-chlorophenol, 3-chlorophenol, 2,3-dichlorophenol and 3,4-dichlorophenol) from water and peach juice samples followed by high performance liquid chromatography-ultraviolet detection. Good linearity was observed in the range 1.0-100.0 ng mL(-1) and 2.0-100.0 ng mL(-1) for water and peach juice sample, respectively. The limits of detection (S/N=3) were between 0.10 and 0.30 ng mL(-1). The relative standard deviations were less than 5.3% and the recoveries of the method for the compounds were in the range from 87.8% to 102.3%. The results demonstrated that the MPC had a high adsorptive capability toward the four chlorophenols from water and peach juice samples.

On-line sample concentration and determination of cationic alkaloids in human plasma by micelle to solvent stacking in capillary zone electrophoresis

A sensitive method for the determination of three cationic alkaloids (berberine, palmatine and jatrorrhizine) from human plasma samples was developed by micelle to solvent stacking (MSS) in capillary zone electrophoresis (CZE). In MSS, the sample preconcentration mainly relies on the reversal in the effective electrophoretic mobility of the analytes at the boundary zone between the sample and CZE background solution (BGS). Under the optimized conditions, the sensitivity enhancement factors achieved in terms of corrected peak area were in the range from 47 to 53 for the alkaloids. The limits of detection (LODs) (S/N=3) for berberine, palmatine and jatrorrhizine were 0.01, 0.01 and 0.02μg/mL, respectively. The intraday (n=6) and interday repeatabilities (n=12) expressed as the relative standard deviations (RSDs) were less than 6.9% in terms of peak height and less than 7.3% in terms of corrected peak area, respectively. The recoveries of the method for the three alkaloids were in the range of 95.9-101.5% with peak height as the quantitative signal, and 92.6-103.6% with corrected peak area as the quantitative signal, respectively. The MSS-CZE method proved to be suitable for the analysis of the alkaloids in human plasma samples.

Preparation of a Co-doped hierarchically porous carbon from Co/Zn-ZIF: An efficient adsorbent for the extraction of trizine herbicides from environment water and white gourd samples.

A Co-doped hierarchically porous carbon (Co/HPC) was synthesized through a facile carbonization process by using Co/ZIF-8 as the precursor. The textures of the Co/HPC were investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, vibration sample magnetometry and nitrogen adsorption-desorption isotherms. The results showed that the Co/HPC is in good polyhedral shape with uniform size, sufficient magnetism, high surface area as well as hierarchical pores (micro-, meso- and macropores). To evaluate the extraction performance of the Co/HPC, it was applied as a magnetic adsorbent for the enrichment of triazine herbicides from environment water and white gourd samples prior to high performance liquid chromatographic analysis. The main parameters that affected the extraction efficiency were investigated. Under the optimum conditions, a good linearity for the four triazine herbicides was achieved with the correlation coefficients (r) higher than 0.9970. The limits of detection, based on S/N=3, were 0.02 ng/mL for water and 0.1-0.2 ng/g for white gourd samples, respectively. The recoveries of all the analytes for the method fell in the range from 80.3% to 120.6%.

Triphenylamine-based hypercrosslinked organic polymer as adsorbent for the extraction of phenylurea herbicides

A hypercrosslinked organic polymer material (named as PPTPA) was prepared by a simple one-step self-polycondensation of triphenylamine. A series of characterization experiments, including N2 adsorption, scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectra, and thermogravimetric analysis, were carried out to evaluate the morphology, structure and other intrinsic properties of the PPTPA. To investigate its adsorption performance, the PPTPA was used as the solid-phase extraction adsorbent for the extraction of phenylurea herbicides from water, milk and tomato juice samples followed by high-performance liquid chromatographic analysis. Under optimum conditions, good linearity for the analytes was observed in the range of 0.05-40.0ngmL-1, 0.1-40.0ngmL-1 and 0.5-40.0ngmL-1 for water, milk and tomato juice samples, respectively. The established method also showed low limits of detection (S/N=3) in the range of 0.008-0.01ngmL-1, 0.01-0.03ngmL-1 and 0.05-0.1ngmL-1 for water, milk and tomato juice samples, respectively. The possible adsorption mechanism of the PPTPA towards the analytes was investigated, and the results demonstrated that the hydrogen bonding was the main interaction force between the PPTPA and the analytes. It suggests that the PPTPA can serve as a promisingadsorbent for the efficient pre-enrichment of organic compounds with more hydrogen-bonding donor sites.

Determination of Carbamate Pesticides in Vegetables by Octadecyl Modified Graphene Reinforced Hollow Fiber Liquid Phase Microextraction Combined with High-Performance Liquid Chromatography

A novel adsorbent, octadecyl modified graphene, was prepared for hollow fiber liquid phase microextraction to increase the efficiency of the preconcentration process. The modified material was employed for the isolation of metolcarb, carbaryl, isoprocarb, and diethofencarb from vegetables prior to determination by high-performance liquid chromatography with diode array detection. Octadecyl modified graphene dispersed in 1-octanol served as the acceptor phase of the sorbent, resulting in enhanced efficiency. The optimization of several parameters was carried out to achieve the maximum efficiency. Under the optimized conditions, the calibration curve was linear from 0.5 to 100.0 nanograms per gram for carbaryl and 1.0 to 100.0 nanograms per gram for the other analytes with correlation coefficients (r) between 0.9952 and 0.9990. The limits of detection for the carbamates were from 0.2 to 0.6 nanogram per gram. The recoveries of the analytes ranged from 90.3 to 107.4 percent, indicating the excellent performance of the method for the determination of carbamates in vegetables.

Synthesis of Magnetic Fe3O4 Modified Graphene Nanocomposite and its Application on the Adsorption of some Dyes from Aqueous Solution

A novel magnetic Fe3O4 modified reduced graphene oxide nanocomposite (Fe3O4@SiO2-rGO) was prepared by a covalent bonding method. The morphology and properties of the Fe3O4@SiO2-rGO were characterized by transmission electron microscopy and X-ray diffraction. The prepared Fe3O4@SiO2-rGO was tested as an efficient adsorbent for the removal of some dyes from aqueous solution for the first time. The performance of Fe3O4@SiO2-rGO was evaluated using methylene blue and neutral red as model compounds. Experiments were carried out to investigate the adsorption kinetics and adsorption capacity of the adsorbent and the effect of the adsorbent dosage and sample solution pH on the removal of the dyes. Kinetic data were well fitted by pseudo second-order model. The Langmuir model and the Freundlich model were used to study the adsorption isotherms. The Fe3O4@SiO2-rGO nanocomposite showed to be a highly efficient adsorbent with the advantage of separation convenience. The thermodynamic parameters indicated that the adsorption of the dyes onto the Fe3O4@SiO2-rGO was a spontaneous process.

Application of a solid-phase microextraction fiber coated with a graphene oxide-poly(dimethylsiloxane) composite for the extraction of triazoles from water.

A solid-phase microextraction fiber was prepared by mixing graphene oxide and hydroxyl-terminated polydimethylsiloxane together and then coating the mixture on the surface of etched stainless-steel wire by sol-gel technology. After aging by heating, the graphene oxide-polydimethylsiloxane composite coated fiber was used for the direct solid phase microextraction of triazole fungicides from water samples. The properties of the graphene oxide-polydimethylsiloxane coating were characterized by transmission electron microscopy and thermogravimetric analysis. And the chemical stability of the coating was tested as well. Several important experimental parameters that could influence the extraction efficiency such as desorption temperature and time, extraction temperature and time, sample pH and stirring rate, were investigated and optimized. Under the optimized conditions, the limits of detection were in the range from 0.01 to 0.03 μg/L. The results indicated that the homemade fiber had the advantages of good thermal and chemical stability and high extraction efficiency, which was successfully applied to the analysis of triazoles in water samples.