Capillary electrophoretic analysis of arsenic species with indirect laser induced fluorescence detection

The development of a method for determining arsenic species by capillary zone electrophoresis (CZE) with indirect laser-induced fluorescence (LIF) is described in this paper. The buffer pH, the concentration of fluorescein, the nature and the concentration of the background electrolytes (BGEs) were defined. When 2.0 mM NaHCO3 (pH 9.28) with 10(-7) M fluorescein was used as the buffer, arsenite (As(lll), dimethylarsonic acid (DMA), monomethylarsonic acid (MMA), and arsenate (As(V)) were all separated from one another. The limits of detection for the four arsenic species were p p in the range of 0.12-0.54 mg/L. This method was used in the analysis of spiked arsenic species in tap and mineral water to demonstrate its usefulness. The results showed that both the recovery and the reproducibility of the developed method were acceptable.

Determination of arsenic species by capillary zone electrophoresis with large-volume field-amplified stacking injection

Determination of arsenic species by large-volume field amplified stacking injection-capillary zone electrophoresis (LV-FASI-CZE) is reported in this paper. Whole column injection was employed. The optimum buffer pH for the separation of weak acids was discussed. It was found that the optimum buffer to analyze the stacked arsenate (As(V)), monomethylarsonate (MMA), and dimethylarsinate (DMA) was 25 mm phosphate at pH 6.5. However, the optimum buffer to analyze the concentrated arsenite (As(III)) was 20 mm phosphate - 10 mm borate at pH 9.28. The limits of detection of the method developed were 0.026 mg/L for As(III), 0.023 mg/L for As(V), 0.043 mg/L for MMA, and 0.018 mg/L for DMA. An enrichment factor of 34-100 for several arsenic species was obtained. In the end, this method was applied to determine the arsenic concentration in the environmental reference materials to show the usefulness of the method developed.

Effects of temperature, glucose and inorganic nitrogen inputs on carbon mineralization in a Tibetan alpine meadow soil

High levels of available nitrogen (N) and carbon (C) have the potential to increase soil N and C mineralization We hypothesized that with an external labile C or N supply alpine meadow soil will have a significantly higher C mineralization potential and that temperature sensitivity of C mineralization will increase To test the hypotheses an incubation experiment was conducted with two doses of N or C supply at temperature of 5 15 and 25 C Results showed external N supply had no significant effect on CO2 emission However external C supply increased CO2 emission Temperature coefficient (Q(10)) ranged from 113 to 1 29 Significantly higher values were measured with C than with N addition and control treatment Temperature dependence of C mineralization was well-represented by exponential functions Under the control CO2 efflux rate was 425 g CO2-Cm-2 year(-1) comparable to the in situ measurement of 422 g CO2-Cm-2 year(-1) We demonstrated if N is disregarded microbial decomposition is primarily limited by lack of labile C It is predicted that labile C supply would further increase CO2 efflux from the alpine meadow soil (C) 2010 Elsevier Masson SAS All rights reserved

Drivers of soil net nitrogen mineralization in the temperate grasslands in Inner Mongolia, China

Soil net nitrogen mineralization (NNM) of four grasslands across the elevation and precipitation gradients was studied in situ in the upper 0-10 cm soil layer using the resin-core technique in Xilin River basin, Inner Mongolia, China during the growing season of 2006. The primary objectives were to examine variations of NNM among grassland types and the main influencing factors. These grasslands included Stipa baicalensis (SB), Aneulolepidum Chinense (AC), Stipa grandis (SG), and Stipa krylovii (SK) grassland. The results showed that the seasonal variation patterns of NNM were similar among the four grasslands, the rates of NNM and nitrification were highest from June to August, and lowest in September and October during the growing season. The rates of NNM and nitrification were affected significantly by the incubation time, and they were positively correlated with soil organic carbon content, total soil nitrogen (TN) content, soil temperature, and soil water content, but the rates of NNM and nitrification were negatively correlated with available N, and weakly correlated with soil pH and C:N ratio. The sequences of the daily mean rates of NNM and nitrification in the four grasslands during the growing season were AC > SG > SB > SK, and TN content maybe the main affecting factors which can be attributed to the land use type.

In vivo mineralization and osteogenesis of nanocomposite scaffold of poly (lactide-co-glycolide) and hydroxyapatite surface-grafted with poly(L-lactide)

Nanocomposite of hydroxyapatite (HAP) surface-grafted with poly(L-lactide) (PLLA) (g-HAP) shows a wide application for bone fixation materials due to its improved interface compatibility, mechanical property and biocompatibility in our previous study. In this paper, a 3-D porous scaffold of g-HAP/poly (lactide-co-glycolide) (PLGA) was fabricated using the solvent casting/particulate leaching method to investigate its applications in bone replacement and tissue engineering. The composite of un-grafted HAP/PLGA and neat PLGA were used as controls. Their in vivo mineralization and osteogenesis were investigated by intramuscular implantation and replacement for repairing radius defects of rabbits. After surface modification, more uniform distribution of g-HAP particles but a lower calcium exposure on the surface of g-HAP/PLGA was observed. Intramuscular implantation study showed that the scaffold of g-HAP/PLGA was more stable than that of PLGA, and exhibited similar mineralization and biodegradability to HAP/PLGA at the 12-20 weeks post-surgery.

A novel 2D arsenic vanadate network grafted with a transition metal complex: [Cu(phen)][(VV4As2O19)-V-IV-As-V]center dot 0.5H(2)O

A novel organic-inorganic hybrid compound [Cu(phen)](2)[(VV4As2O19)-V-IV-As-V-O-V].0.5H(2)O 1 has been hydrothermally synthesized. Its structure, determined by single crystal X-ray diffraction, exhibits an unusual two-dimensional arsenic vanadate layered network grafted with the [Cu(phen)](2+) complex. The chelating phen ligands project perpendicularly beyond the inorganic layer. Variable temperature magnetic susceptibility studies indicate that both ferro- and antiferro-magnetic interactions exist in 1.

Determination of Total Arsenic and Arsenic Metabolites in Human Liver Hepatocytes

The effects of direct sampling and three digestion methods were investigated on the determination of arsenic in Chang liver hepatocytes after ultrasonic disintegration were investigated. The results showed that the efficiency of microwave digestion and obturator digestion was better than cold digestion and direct sampling. The day precision (present as RSD) of microwave digestion and obturator digestion were 2.1% and 1.2% the inter-day precision were 1.2% and 2.0%, respectively. The spike recovery for the total As in the sample is 95.7% - 108.1%. The As detection limits with these four sample treatment methods (including direct sampling) were 0.74 - 0.93 mu g/L. In addition, arsenic speciation in Chang liver hepatocytes was also analyzed using the hyphenated technique of high performance liquid chromatography coupled with inductively coupled plasma-mass spectrometry. The experimental results indicated that dimethylarsinic acid (DMA) and an intermediate metabolite of DMA were found lit Chang liver hepatocytes besides inorganic arsenic (As(III) and As(V)).

The behaviors and sources of dissolved arsenic and antimony in Bohai Bay

In this paper, we determined the concentrations of antimony species (antimonite (Sb(III)), antimonate (Sb(V)) and dissolved inorganic antimony (DISb)) and arsenic, in Bohai Bay seawaters, as well as the relationships of the analytes with environmental factors such as seawater characteristics (e.g., suspended particulate material (SPM), salinity and total organic carbon (TOC)), heavy metals, nutrients and phytoplankton species, and evaluated the sources of arsenic and antimony. Dissolved arsenic and antimony concentrations in the surface waters were ranging spatially from 1.03 to 1.26 ng/ml and 0.386 to 1.075 ng/ml, with mean values of 1.18 and 0.562 ng/ml, respectively. Sb(V) as the prominent chemical species constituted about 89%. Regarding arsenic concentrations in the surface waters, there was a tendency for a small variation. However, antimony species concentrations were much variable than arsenic. The highest arsenic and antimony concentrations were found near the Haihe Estuary. These distribution patterns were controlled mainly by environmental factors, biological activities and sources. In this region, DISb and Sb(V) negatively correlated with salinity. Besides, arsenic and antimony correlated well with the nutrients, chlorophyll a and phytoplankton, implying that arsenic and antimony had been involved in biological cycling. In addition, according to our estimate, about 333.5 x 10(8) mg/year of arsenic and 454.2 x 10(8) mg/year of antimony reached Bohai Bay via rivers. (C) 2010 Elsevier Ltd. All rights reserved.

Determination of trace arsenic and selenium in jellyfish by microwave digestion-hydride generation-atomic fluorescence spectrometry

A method of hydride generation-atomic fluorescence spectrometry was proposed in the present paper for the determination of trace arsenic and selenium in jellyfish. The samples were treated by the combination of microwave digestion and lyophilization. The optimal conditions for treating and analyzing samples were established. The problem of the effect of the superfluous acid in the digesting solution on the results was solved, and the influence of coexisting foreign ions on the determination of arsenic and selenium was investigated. The accuracy of the method was confirmed by the method of standard additions. This method proved to be simple, rapid and repeatable, and is suitable for the analysis of biologic samples containing water.