A comprehensive exploration on distribution, risk assessment, and source quantification of heavy metals in the multi-media environment from Shaying River Basin, China.

Comprehensively understand the distribution of pollutants in the multi-media environment at basin scale is of major importance to the ecological risk assessment and pollution control. In this study, multi-media contamination characteristics of eight heavy metals in the water, soil, and sediment from the Shaying River Basin of China have been analyzed to probe their ecological risks and potential sources. Results revealed that heavy metal concentrations in pore water were higher than those in surface water. While the mean concentrations of most heavy metals increased follow the order of bankside soil (BS)

Homogeneous liquid-liquid extraction combined with high performance liquid chromatography-fluorescence detection for determination of polycyclic aromatic hydrocarbons in vegetables.

In this article, homogeneous liquid-liquid extraction (HOLLE), combined with HPLC-fluorescence detector (HPLC-FLD), has been developed for the extraction and determination of polycyclic aromatic hydrocarbons (PAHs) in vegetables. ACN was used as extraction solvent for the extraction of target analytes from vegetables. When the previous extraction process was over, the ACN extract was transferred to the water-immiscible organic phase, tetrachloroethane, used as extraction solvent in HOLLE procedures. Under the optimum conditions, repeatability was carried out by spiking PAHs at concentration level of 12.5 microg/kg, the RSDs varied between 1.1 and 8.5% (n = 3). The LODs, based on S/N of 3, ranged from 0.025 to 0.25 microg/kg. Relative recoveries of PAHs from cucumber and long crooked squash samples were in the range of 72.4-104.9% and 65.5-119.3%, respectively. Compared with the conventional extraction method, the proposed method has the advantage of being quick, easy to operate, and having low consumption of organic solvent.

Determination of four aromatic amines in water samples using dispersive liquid-liquid microextraction combined with HPLC.

A new method for the determination of four aromatic amines in water samples was developed by using dispersive liquid-liquid microextraction (DLLME) technique combined with HPLC-variable wavelength detection (HPLC-VWD). In this extraction method, 0.50 mL methanol (as dispersive solvent) containing 25.0 microL tetrachloroethane (as extraction solvent) was rapidly injected by a syringe into 5.00 mL water sample. Accordingly, a cloudy solution was formed. After centrifugation for 2 min at 4000 rpm, the fine droplets of the tetrachloroethane containing the analytes were sedimented in the bottom of the conical test tube (7+/-0.2 microL). Then, 5.0 microL of the settled phase was determined by HPLC-VWD. Parameters such as the kind and volume of extraction solvent and dispersive solvent, extraction time, and salt concentration were optimized. Under the optimum conditions, the enrichment factors ranged from 41.3 to 94.5. Linearity was observed in the range of 5-5000 ng/mL. The LODs based on S/N of 3 ranged from 0.8 to 1.8 ng/mL. The RSDs (for 400 ng/mL of p-toluidine and o-chloroaniline, 100 ng/mL of p-chloroaniline and p-bromoaniline) varied from 4.1 to 5.3% (n=6). The water samples collected from rivers and lakes were successfully analyzed by the proposed method and the relative recoveries were in the range of 85.4-111.7% and 90.2-101.3%, respectively.

Recent Advances in the Cancer Bioimaging with Graphene Quantum Dots.

Fluorescent graphene quantum dots (GQDs) have attracted increasing interest in cancer bioimaging due to their stable photoluminescence (PL), high stability, low cytotoxicity, and good biocompatibility. In this review, we present the synthesis and chemical modification of GQDs firstly, and then introduce their unique physical, chemical, and biological properties like the absorption, PL, and cytotoxicity of GQDs. Finally and most importantly, the recent applications of GQDs in cancer bioimaging are demonstrated in detail, in which we focus on the biofunctionalization of GQDs for specific cancer cell imaging and real-time molecular imaging in live cells. We expect this work would provide valuable guides on the synthesis and modification of GQDs with adjustable properties for various biomedical applications in the future.

Fabrication of Hierarchical Layer-by-Layer Assembled Diamond-based Core-Shell Nanocomposites as Highly Efficient Dye Absorbents for Wastewater Treatment.

The effective chemical modification and self-assembly of diamond-based hierarchical composite materials are of key importance for a broad range of diamond applications. Herein, we report the preparation of novel core-shell diamond-based nanocomposites for dye adsorption toward wastewater treatment through a layer-by-layer (LbL) assembled strategy. The synthesis of the reported composites began with the carboxyl functionalization of microdiamond by the chemical modification of diamond@graphene oxide composite through the oxidation of diamond@graphite. The carboxyl-terminated microdiamond was then alternatively immersed in the aqueous solution of amine-containing polyethylenimine and carboxyl-containing poly acrylic acid, which led to the formation of adsorption layer on diamond surface. Alternating (self-limiting) immersions in the solutions of the amine-containing and carboxyl-containing polymers were continued until the desired number of shell layers were formed around the microdiamond. The obtained core-shell nanocomposites were successfully synthesized and characterized by morphological and spectral techniques, demonstrating higher surface areas and mesoporous structures for good dye adsorption capacities than nonporous solid diamond particles. The LbL-assembled core-shell nanocomposites thus obtained demonstrated great adsorption capacity by using two model dyes as pollutants for wastewater treatment. Therefore, the present work on LbL-assembled diamond-based composites provides new alternatives for developing diamond hybrids as well as nanomaterials towards wastewater treatment applications.

Application of dispersive liquid-liquid microextraction for the analysis of triazophos and carbaryl pesticides in water and fruit juice samples.

In this work, a simple, rapid and sensitive sample pretreatment technique, dispersive liquid-liquid microextraction (DLLME) coupled with high performance liquid chromatography-fluorescence detection (HPLC-FLD), has been developed to determine carbamate (carbaryl) and organophosphorus (triazophos) pesticide residues in water and fruit juice samples. Parameters, affecting the DLLME performance such as the kind and volume of extraction and dispersive solvents, extraction time and salt concentration, were studied and optimized. Under the optimum extraction conditions (extraction solvent: tetrachloroethane, 15.0 microL; dispersive solvent: acetonitrile, 1.0 mL; no addition of salt and extraction time below 5s), the performance of the proposed method was evaluated. The enrichment factors for the carbaryl and triazophos were 87.3 and 275.6, respectively. The linearity was obtained in the concentration range of 0.1-1000 ng mL(-1) with correlation coefficients from 0.9991 to 0.9999. The limits of detection (LODs), based on signal-to-noise ratio (S/N) of 3, ranged from 12.3 to 16.0 pg mL(-1). The relative standard deviations (RSDs, for 10 ng mL(-1) of carbaryl and 20 ng mL(-1) of triazophos) varied from 1.38% to 2.74% (n=6). The environmental water (at the fortified level of 1.0 ng mL(-1)) and fruit juice samples (at the fortified level of 1.0 and 5.0 ng mL(-1)) were successfully analyzed by the proposed method, and the relative recoveries of them were in the range of 80.4-114.2%, 89.8-117.9% and 86.3-105.3%, respectively.

Dispersive liquid-liquid microextraction combined with gas chromatography-electron capture detection for the determination of polychlorinated biphenyls in soils.

In this article, dispersive liquid-liquid microextraction (DLLME) and gas chromatography-electron capture detection (GC-ECD) were presented for the extraction and determination of five polychlorinated biphenyls (PCBs) in soil samples. Acetone was used as extraction solvent for the extraction of PCBs from soil samples. In DLLME, the target analytes in the extraction solvent were rapidly transferred from the acetone extract to chlorobenzene when the extraction process began. The main advantages of this method are quick speed, high enrichment factor, high recovery and good repeatability. Under the optimum conditions, the method yields a linear calibration curve in the concentration range from 2 to 2000 microg kg(-1)for PCB 52, and 0.4 to 400 microg kg(-1) for other target analytes. Coefficients of correlation (r(2)) ranged from 0.9993 to 0.9999. The repeatability was tested by spiking soil samples at a concentration level of 10 microg kg(-1) for PCBs. The relative standard deviations (RSDs, n=11) varied between 2.2% and 6.4%. The limits of detection (LODs), based on signal-to-noise (S/N) of 3, were between 0.20 and 0.50 microg kg(-1). The relative recoveries of the five PCBs from soil S1, S2 and S3 at spiking levels of 10, 20 and 50 microg kg(-1) were in the range of 88.70-103.8%, 82.50-106.3% and 82.30-113.6%, respectively. Therefore, DLLME combined with GC-ECD can be successfully applied for the determination of trace PCB residues in real soil samples.

Dispersive liquid-liquid microextraction followed by reversed phase-high performance liquid chromatography for the determination of polybrominated diphenyl ethers at trace levels in landfill leachate and environmental water samples.

A simple, rapid and efficient method, dispersive liquid-liquid microextraction (DLLME), has been developed for the extraction and preconcentration of polybrominated diphenyl ethers (PBDEs) in water samples. The factors influencing microextraction efficiencies, such as the kind and volume of extraction and dispersive solvent, the extraction time and the salt effect, were optimized. Under the optimum conditions (sample volume: 5 mL; extraction solvent: tetrachloroethane, 20.0 microL; dispersive solvent: acetonitrile, 1.00 mL; extraction time: below 5s and without salt addition), the enrichment factors and extraction recoveries were high and ranged from 268 to 305 and 87.0 to 119.1%, respectively. Linearity was observed in the range 0.05-50 ng mL(-1) for BDE-28 and BDE-99, and 0.1-100 ng mL(-1) for BDE-47 and BDE-209, respectively. Coefficients of correlation (r(2)) ranged from 0.9995 to 0.9999. The repeatability study was carried out by extracting the spiked water samples at concentration levels of 50 ng mL(-1) for BDE-28 and BDE-99, and 100 ng mL(-1) for BDE-47 and BDE-209, respectively. The relative standard deviations (R.S.D.s) varied between 3.8 and 6.3% (n=5). The limits of detection (LODs), based on signal-to-noise ratio (S/N) of 3, ranged from 12.4 to 55.6 pg mL(-1) (the wavelength of detector at 226 nm). The relative recoveries of PBDEs from tap, lake water and landfill leachate samples at spiking levels of 5, 10 and 50 ng mL(-1) were in the range of 89.7-107.6%, 114.3-119.1% and 87.0-90.9%, respectively. As a result, this method can be successfully applied for the determination of PBDEs in landfill leachate and environmental water samples.

Homogeneous liquid-liquid extraction combined with gas chromatography-electron capture detector for the determination of three pesticide residues in soils.

In this study, a new method was developed for analyzing malathion, cypermethrin and lambda-cyhalothrin from soil samples by using homogeneous liquid-liquid extraction (HLLE) and gas chromatography with electron capture detector (GC-ECD). Acetone was used as extraction solvent for the extraction of target pesticides from soil samples. When the extraction process was finished, the target analytes in the extraction solvent were rapidly transferred from the acetone extract to carbon tetrachloride, using HLLE. Under the optimum conditions, linearity was obtained in the range of 0.05-40 microg kg(-1) for malathion, 0.04-10 microg kg(-1) for lambda-cyhalothrin and 0.05-50 microg kg(-1) for cypermethrin, respectively. Coefficients of correlation (r(2)) ranged from 0.9993 to 0.9998. The repeatability was carried out by spiking soil samples at concentration levels of 2.5 microg kg(-1) for lambda-cyhalothrin, and 10 microg kg(-1) for malathion and cypermethrin, respectively. The relative standard deviations (RSDs) varied between 2.3 and 9.6% (n=3). The limits of detection (LODs), based on signal-to-noise ratio (S/N) of 3, varied between 0.01 and 0.04 microg kg(-1). The relative recoveries of three pesticides from soil A1, A2 and A3 at spiking levels of 2.5, 5 and 10 microg kg(-1) were in the range of 82.20-91.60%, 88.90-110.5% and 77.10-98.50%, respectively. In conclusion, the proposed method can be successfully applied for the determination of target pesticide residues in real soil samples.