Xiaoxing Ma

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.

Graphene grafted silica-coated Fe3O4 nanocomposite as absorbent for enrichment of carbamates from cucumbers and pears prior to HPLC.

In this paper, a novel graphene (G) grafted silica-coated Fe3O4 nanocomposite was fabricated by the chemical bonding of G onto the surface of silica-coated Fe3 O4 nanoparticles. Some carbamates (metolcarb, carbaryl, pirimicarb, and diethofencarb) in cucumber and pear samples were enriched by this nanocomposite prior to their determination by HPLC with UV detection. Experimental parameters that may affect the extraction efficiency were investigated. Under the optimum conditions, a linear response was achieved in the concentration range of 0.5-100.0 ng/g for metolcarb, carbaryl, and diethofencarb, and 1.0-100 ng/g for pirimicarb with the correlation coefficients (r) ranging from 0.9956 to 0.9984. The LOD (S/N = 3) of the method were found to be in the range from 0.08 to 0.2 ng/g. The RSDs were in the range from 2.4 to 5.8%. The results indicated that the G grafted silica-coated Fe3 O4 nanocomposite was stable and efficient for magnetic SPE and has a great application potential for the preconcentration of other organic pollutants from real samples.

Magnetic solid-phase extraction of neonicotinoid pesticides from pear and tomato samples using graphene grafted silica-coated Fe3O4 as the magnetic adsorbent

A novel graphene grafted silica-coated Fe3O4 (Fe3O4@SiO2-G) was synthesized and used as an efficient magnetic solid-phase extraction adsorbent for the simultaneous extraction of four neonicotinoid pesticides (thiamethoxam, imidacloprid, acetamiprid and thiacloprid) from pear and tomato samples followed by high performance liquid chromatography-diode array detection. After extraction, the adsorbent could be conveniently separated from the sample solution by an external magnetic field. The main experimental parameters affecting the extraction efficiency were investigated in detail. Under the optimum conditions, a rapid and effective determination of the neonicotinoid pesticides in pear and tomato samples was achieved. The limits of detection (S/N = 3) of the method for the neonicotinoids ranged from 0.08 to 0.15 ng g−1. Good linearity and reproducibility were obtained. The recoveries of the method were in the range from 93.1% to 107.4%.

Extraction of carbamate pesticides in fruit samples by graphene reinforced hollow fibre liquid microextraction followed by high performance liquid chromatographic detection

Graphene reinforced hollow fibre liquid phase microextraction combined with high performance liquid chromatography-diode array detection was developed for the determination of some carbamate pesticides (metolcarb, carbaryl, isoprocarb, and diethofencarb) in fruit samples. The main parameters that affect the extraction efficiency for the carbamates were investigated. Under the optimum conditions, a good linearity was observed in the range of 1.0-100.0 ng g(-1) for carbaryl and 3.0-100.0 ng g(-1) for the other three analytes, with the correlation coefficients (r) of 0.9965-0.9993. The limits of detection of the method ranged from 0.2 to 1.0 ng g(-1). The relative standard deviations were in the range from 6.2% to 7.8%. The results indicated that the developed method is sensitive and efficient for the determination of the carbamate pesticides in fruit samples.

Magnetic three-dimensional graphene solid-phase extraction coupled with high performance liquid chromatography for the determination of phthalate esters in fruit juice

In this paper, a three-dimensional graphene-based magnetic nanocomposite (3D-G-Fe3O4) was synthesized and used as an effective adsorbent for the extraction of four phthalate esters (dimethyl(o-)phthalate, diethyl(o-)phthalate, diallyo(o-)phthalate and bis(2-propylheptyl)phthalate) from fruit juice prior to high performance liquid chromatography analysis. The three-dimensional nanoporous structure of the 3D-G endows the new material with a high adsorption capacity. The properties and morphology of the 3D-G-Fe3O4 were characterized by transmission electron microscopy, scanning electron microscopy and infrared spectroscopy. Several experimental parameters affecting the extraction efficiencies, such as the amount of the 3D-G-Fe3O4, extraction time, sample pH, salt addition and desorption conditions were optimized. Under the optimum conditions, the limits of detection (S/N = 3) of the method for the analytes were between 0.04 and 0.13 ng mL−1. The recoveries of the method for the analytes were in the range from 87.0% to 97.8%. The result showed that the 3D-G-Fe3O4 has an excellent adsorption capacity for the analytes.

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.

Mesoporous carbon reinforced hollow fiber liquid- phase microextraction for the enrichment of phenylurea herbicides followed by their determination with high performance liquid chromatography

In this paper, a new sample preparation method based on mesoporous carbon reinforced hollow fiber liquid phase microextraction (MC-HF-LPME) was developed for the extraction of some phenylurea herbicides (chlortoluron, isoproturon, monolinuron and buturon) in river water and soil samples prior to high performance liquid chromatography-diode array detection. Mesoporous carbon was synthesized using MCM-41 as a template and sucrose as a carbon precursor. The as-prepared mesoporous carbon was characterized by SEM, TEM and nitrogen adsorption. Several important parameters that affect the extraction efficiencies, such as concentration of ordered porous carbon, fiber length, extraction time, sample solution pH, salt addition and stirring rate, were investigated and optimized. Under the optimum conditions, the linearity for buturon was in the range of 0.3–100.0 ng mL−1 and 5.0–300.0 ng g−1 for river water and soil samples, respectively. The linearity for the other three analytes was in the range of 0.2–100.0 ng mL−1 for the river water sample and 2.0–300.0 ng g−1 for the soil sample. The limits of detection (S/N = 3) of the method ranged from 0.05 to 0.1 ng mL−1 for the river water sample and 0.5 to 1.0 ng g−1 for the soil sample. The results indicated that the developed method is a simple, efficient and environmentally friendly method for the extraction and determination of phenylurea herbicides in river water and soil samples.