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1.
J Am Chem Soc ; 141(44): 17703-17712, 2019 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-31603672

RESUMO

Physical adsorption of gas molecules in microporous materials is an exothermic process, with desorption entropy driving a decrease in uptake with temperature. Enhanced gas sorption with increasing temperature is rare in porous materials and is indicative of sorbate initiated structural change. Here, sorption of C2H6, C3H6, and C3H8 in a flexible microporous metal-organic framework (MOF) {Cu(FPBDC)]·DMF}n (NKU-FlexMOF-1) (H2FPBDC = 5-(5-fluoropyridin-3-yl)-1,3-benzenedicarboxylic acid) that increases with rising temperature over a practically useful temperature and pressure range is reported along with other small molecule and hydrocarbon sorption isotherms. Single X-ray diffraction studies, temperature-dependent gas sorption isotherms, in situ and variable temperature powder X-ray diffraction experiments, and electronic structure calculations were performed to characterize the conformation-dependent sorption behavior in NKU-FlexMOF-1. In total, the data supports that the atypical sorption behavior is a result of loading-dependent structural changes in the flexible framework of NKU-FlexMOF-1 induced by sorbate-specific guest-framework interactions. The sorbates cause subtle adaptations of the framework distinct to each sorbate providing an induced-fit separation mechanism to resolve chemically similar hydrocarbons through highly specific sorbate-sorbent interactions. The relevant intermolecular contacts are shown to be predominantly repulsion and dispersion interactions. NKU-FlexMOF-1 is also found to be stable in aqueous solutions including toleration of pH changes. These experiments demonstrate the potential of this flexible microporous MOF for cost and energy efficient industrial hydrocarbon separation and purification processes. The efficacy for the separation of C3H6/C3H8 mixtures is explicitly demonstrated using NKU-FlexMOF-1a (i.e., activated NKU-FlexMOF-1) for a particular useful temperature range.

2.
Biosens Bioelectron ; 146: 111751, 2019 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-31605988

RESUMO

Detection of nitrite is important for environmental safety and human health, and the development of high-performance sensors for accurate detection of nitrite is highly desirable. Herein, a highly sensitive graphene electrochemical transistor (GECT) nitrite sensor was designed and fabricated for the first time. A single layer of graphene was placed between the source and drain electrodes by the wetting transfer method to act as channel for the transistor. Au nanoparticles modified reduced graphene oxide nanocomposites (AuNPs/RGO) were electrodeposited at the transistor gate to improve its catalytic oxidation performance of nitrite with optimized electrodeposition conditions. The sensing principle was attributed to changes in effective gate voltage applied to GECT induced by electrooxidation of nitrite at gate electrodes. Due to the high carrier mobility of graphene in the channel and the excellent electrocatalytical activity of AuNPs/RGO on the gate, the obtained sensor device exhibited an exceedingly low detection limit (0.1 nM nitrite) and ultra-wide linear range from 0.1 nM to 7 µM and from 7 to 1000 µM, which are comparable or superior to the performance of large-scale instruments (e.g. chromatography, spectrophotometry, and spectrofluorimetry etc.). The GECT device also showed good anti-interference performance toward common interfering ions and stable performances. Nitrite in natural lake water has been proven to be monitored by our devices. Therefore, the present novel GECT sensor could act as a desirable practical platform for highly sensitive detection of nitrite in the food and environmental fields.

3.
Mikrochim Acta ; 186(11): 722, 2019 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-31655901

RESUMO

A nanocomposite was prepared from gold and graphene oxide via one-step electrodeposition and used to modify the surface of a gold electrode (Au-Gr/GE) that was then applied to non-enzymatic determination of glucose. The effects of deposition time and supporting substrate on the morphology, structure, and electrochemical properties of the nanocomposite were optimized. The morphologies and crystal structures were characterized by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The results indicate that gold nanoparticles grew on the surface of two-dimensional graphene oxide. The electrocatalytic activity of the modified electrode towards glucose oxidation was evaluated by cyclic voltammetry and amperometric methods at pH 7.4. The Au-Gr/GE, typically operated at a potential of 0.00 V (vs. Ag/AgCl), has a linear response in the 0.05-14 mM and 14-42 mM glucose concentration range, high sensitivity (604 and 267 µA cm-2 mM-1) and a low detection limit (12 µM). The modified GE was applied to quantify glucose in sweat where it exhibited excellent sensitivity and accuracy. Graphical abstract The gold electrode modified with a gold-graphene (Au-Gr/GE) is prepared via a direct electrodeposition. The Au-Gr/GE is used for glucose detection in the neutral solution and it can achieve the effect of non-intrusive detection.

4.
Anal Chim Acta ; 1072: 25-34, 2019 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-31146862

RESUMO

For the first time, a simple electrochemical co-deposition was utilized to synthesis the gold and zirconia nanocomposites modified graphene nanosheets on glassy carbon electrode (Au-ZrO2-GNs/GCE) for electrocatalytic analysis of methyl parathion (MP). According to Field-Emission Scanning Electron Microscopy (FE-SEM), Transmission Electronic Microscopy (TEM) and X-Ray Diffraction (XRD), the gold nanoparticles were uniformly distributed on the surface of graphene-based nanocomposite. The Au-ZrO2-GNs/GCE based sensor exhibited superior capacity for MP detection, ascribed to the strong affinity of zirconia towards the phosphoric group, as well as the high catalytic activity and good conductivity of Au-GNs. The best fabrication and work conditions were then obtained by systematically optimization of the electrodeposition process, pH value and enrichment time. Compared to the gold nanoparticles, zirconia or graphene modified electrodes, AuZrO2-GNs/GCE sensor displayed superior electro-catalytic response toward MP oxidation. The sensor response current of square wave voltammetry was highly linearly correlated with the MP concentrations range of 1-100 ng mL-1 and 100-2400 ng mL-1 with the detection limit of 1 ng mL-1. The Au-ZrO2-GNs/GCE nanocomposite sensor showed excellent accuracy and reproducibility for detection of MP in Chinese cabbage samples, providing a new method for efficient pesticide detection in practical applications.


Assuntos
Técnicas Eletroquímicas , Ouro/química , Grafite/química , Metil Paration/análise , Nanocompostos/química , Zircônio/química , Eletrodos , Tamanho da Partícula , Propriedades de Superfície
5.
Angew Chem Int Ed Engl ; 58(30): 10209-10214, 2019 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-31059186

RESUMO

Simultaneous removal of trace amounts of propyne and propadiene from propylene is an important but challenging industrial process. We report herein a class of microporous metal-organic frameworks (NKMOF-1-M) with exceptional water stability and remarkably high uptakes for both propyne and propadiene at low pressures. NKMOF-1-M separated a ternary propyne/propadiene/propylene (0.5 : 0.5 : 99.0) mixture with the highest reported selectivity for the production of polymer-grade propylene (99.996 %) at ambient temperature, as attributed to its strong binding affinity for propyne and propadiene over propylene. Moreover, we were able to visualize propyne and propadiene molecules in the single-crystal structure of NKMOF-1-M through a convenient approach under ambient conditions, which helped to precisely understand the binding sites and affinity for propyne and propadiene. These results provide important guidance on using ultramicroporous MOFs as physisorbent materials.

6.
Biomed Res Int ; 2019: 6317015, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31001558

RESUMO

Background: Living at a high plateau in a very hostile environment and low oxygen levels often leads to the development of high-altitude polycythemia (HAPC) and gastric mucosal lesions caused by high-level reactive oxygen species (ROS). Hypoxia-inducible factor-1A (HIF-1A) helps maintain oxygen homeostasis by promoting the transcription of various genes and can be affected by ROS levels. To evaluate the molecular mechanism by which HAPC causes the gastric mucosal lesions, the expression of HIF-1A was measured in Tibetans with HAPC and in healthy subjects. Ultrastructural, histopathological, and immunohistochemical analyses were performed in the gastric tissues of both groups, and the expression of HIF-1A in the gastric mucosa was detected using qPCR and Western Blot. Results: The microvessel density and average diameter of gastric mucosal vessels were significantly greater in the HAPC patients than in the healthy subjects (p < 0.05). The number of red blood cells in the gastric mucosa was also significantly higher in the HAPC group than in the healthy subjects (p < 0.05). In addition, the density of the mitochondrial vacuoles and endoplasmic reticulum and pathological apoptosis were significantly increased in the gastric cells from HAPC patients compared to those from the healthy subjects. The levels of ROS and HIF-1A in the gastric mucosa were increased in HAPC patients compared to those in controls (p < 0.05). Conclusions: An increased level of HIF-1A was associated with HAPC development in the stomach of Tibetans living at a high altitude. ROS upregulated the levels of HIF-1A. Thus, ROS-mediated HIF-1A signaling transduction may be the mechanism associated with HAPC-induced gastric lesions.


Assuntos
Doença da Altitude/metabolismo , Mucosa Gástrica/metabolismo , Regulação da Expressão Gênica , Subunidade alfa do Fator 1 Induzível por Hipóxia/biossíntese , Policitemia/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Adulto , Doença da Altitude/patologia , Feminino , Mucosa Gástrica/patologia , Humanos , Masculino , Pessoa de Meia-Idade , Policitemia/patologia , Tibet
7.
Nat Mater ; 17(12): 1128-1133, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30397312

RESUMO

There are great challenges in developing efficient adsorbents to replace the currently used and energy-intensive cryogenic distillation processes for olefin/paraffin separation, owing to the similar physical properties of the two molecules. Here we report an ultramicroporous metal-organic framework [Ca(C4O4)(H2O)], synthesized from calcium nitrate and squaric acid, that possesses rigid one-dimensional channels. These apertures are of a similar size to ethylene molecules, but owing to the size, shape and rigidity of the pores, act as molecular sieves to prevent the transport of ethane. The efficiency of this molecular sieve for the separation of ethylene/ethane mixtures is validated by breakthrough experiments with high ethylene productivity under ambient conditions. This material can be easily synthesized at the kilogram scale using an environmentally friendly method and is water-stable, which is important for potential industrial implementation. The strategy of using highly rigid metal-organic frameworks with well defined and rigid pores could also be extended to other porous materials for chemical separation processes.

8.
Opt Lett ; 43(22): 5647-5650, 2018 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-30439916

RESUMO

We investigate the effects of photonic crystal structures on radiation imaging properties of a ZnO:Ga image converter. The results show that photonic crystal structures can regulate luminescence distribution and spatial resolving power, which is caused by the light extraction and the defect scattering of photonic crystal structures. The present investigation confirms that photonic crystals can improve the imaging properties of existing image converters and proposes a new coupling mode between the photonic crystal image converter and back-end optical devices, which is beneficial to the application of photonic crystals in the field of radiation imaging.

9.
Angew Chem Int Ed Engl ; 57(46): 15183-15188, 2018 Nov 12.
Artigo em Inglês | MEDLINE | ID: mdl-30240522

RESUMO

Separation of propyne/propylene (C3 H4 /C3 H6 ) is more difficult and challenging than that of acetylene/ethylene (C2 H2 /C2 H4 ) because of their closer molecular sizes. A comprehensive screening of a series of metal-organic frameworks with broad types of structures, pore sizes, and functionalities was carried out. UTSA-200 was identified as the best separating material for the removal of trace C3 H4 from C3 H4 /C3 H6 mixtures. Gas sorption isotherms reveal that UTSA-200 exhibits by far the highest C3 H4 adsorption capacity (95 cm3 cm-3 at 0.01 bar and 298 K) and record C3 H4 /C3 H6 selectivity, which was mainly attributed to the suitable dynamic pore size to efficiently block the larger C3 H6 molecule whilst the strong binding sites and pore flexibility capture smaller C3 H4 . This material thus provides record purification capacity for the removal of C3 H4 from a 1:99 (or 0.1:99.9, v/v) C3 H4 /C3 H6 mixture to produce 99.9999 % pure C3 H6 with a productivity of 62.0 (or 142.8) mmol g-1 .

10.
Sci Rep ; 8(1): 4178, 2018 Mar 08.
Artigo em Inglês | MEDLINE | ID: mdl-29520009

RESUMO

A ZnO:Ga single crystal with an applicable size of φ40 × 1 mm was prepared using the hydro-thermal method. The crystal exhibits good crystallinity and scintillation properties with a 63.94-arcsec full-width at half-maximum (FWHM) in the X-ray rocking curve (XRC) spectrum, 8% luminous non-uniformity, emission at 389 nm in the X-ray excited luminescence spectrum, fast response and 5.5% BGO luminous intensity. Furthermore, an X-ray pinhole imaging system of nanosecond temporal resolution with a ZnO:Ga single-crystal image converter was established to diagnose the cathode electron emission spatial distribution of an intense current diode. Results for shutter times of 4 µs and 5 ns were obtained, which directly represent the cathode electron spatial distribution throughout the entire pulse duration and during a certain moment of the pulse, respectively. The results demonstrate that the large ZnO:Ga single crystal can diagnose the spatial distribution of cathode electron emission in an intense current diode with high temporal resolution and provide new solutions for high-temporal-resolution diagnosis of a pulse radiation field.

11.
Appl Radiat Isot ; 131: 67-70, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29173810

RESUMO

This paper presents a Monte Carlo method to obtain the full energy peak efficiency (FEPE) curve for a High Purity Germanium (HPGe) detector, as it is difficult and time-consuming to measure the FEPE curve experimentally. The Geant4 simulation toolkit was adopted to establish a detector model since detector specifications provided by the nominal manufacturer are usually insufficient to calculate the accurate efficiency of a detector. Several detector parameters were optimized. FEPE curves for a given HPGe detectors over the energy range of 59.50-1836keV were obtained and showed good agreements with those measured experimentally. FEPE dependences on detector parameters and source-detector distances were investigated. A best agreement with experimental result was achieved for a certain detector geometry and source-detector distance.

12.
Exp Ther Med ; 14(4): 3780-3787, 2017 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-29042979

RESUMO

The Tibetan high plateau is a low-oxygen environment, which may cause the pathogenesis of high-altitude polycythemia (HAPC). Gastric mucosal lesions (GML) are a common complication of HAPC. The molecular mechanisms involved in HAPC-induced GML have remained to be fully elucidated and were therefore investigated in the present study. Gastric tissues of patients with heavy, HAPC-induced GML and healthy controls were assessed by ultrastructural and histopathological analysis. In addition, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis were used to detect cell apoptosis in the gastric mucosa tissues. Moreover, the expression of genes associated with the phosphoinositide-3 kinase (PI3K) pathway was assessed by RT-qPCR to investigate the mechanism of cell apoptosis in HAPC-induced GML. The results revealed a significant increase in the number of red blood cells, gastric vessels and the diameter of gastric mucosal vessels in HAPC-induced GML patients compared with those in healthy controls. In addition, more red blood cells were distributed in gastric tissue not only at the vascular level but also in the tissue space. The number of vacuoles was increased in the gastric mucosal cells. Furthermore, a significant increase in apoptosis of the gastric mucosal cells was identified. The expression of phosphatase and tensin homolog was significantly higher in gastric mucosa from patients with HAPC-induced GML compared with that in the healthy controls. All of the pathologic changes suggested that significant cell apoptosis occurred in the HAPC-induced GML tissues, which may be associated with the PI3K pathway. These findings may provide novel insight for the treatment of gastric lesions caused by HAPC in the future.

13.
Sci Rep ; 7(1): 2841, 2017 06 06.
Artigo em Inglês | MEDLINE | ID: mdl-28588191

RESUMO

Constipation, mainly manifesting as abdominal discomfort and painful defecation, is considered as a chronic disorder. Due to a lack of effective therapy, it imposes a significant economic burden and greatly impacts patients' quality of life which prompt searches for new, original approaches. Based on the research of vibrating capsule (VC) carried out by Ron et al., we investigated the safety and efficacy of an innovative, multi-mode VC in terms of its effect on defecation in animal studies. The parameters associated with different operation modes of VCs can be detected and adjusted by smartphone controlled external configuration device (ECD). The results of blood tests, physiological parameters, CT scan and pathological examination showed no significant abnormality, which undoubtedly confirmed the safety of VCs. For efficacy studies, defecation frequency of beagles increased after administration of these capsules without influence on stool characters. Meanwhile, the mean time of capsule evacuation tended to be reduced while showing no significant difference between different modes. In summary, this study elucidates the safety and effectiveness of VC in prompting the passage of gastrointestinal walls thus greatly increasing the defecation frequency. This study innovatively displays the promising application of VC in the treatment of constipation.

14.
Phys Chem Chem Phys ; 18(19): 13255-66, 2016 05 21.
Artigo em Inglês | MEDLINE | ID: mdl-27118421

RESUMO

The interfacial interaction of uranium mononitride (UN) with water from the environment unavoidably leads to corrosion of nuclear fuels, which affects a lot of processes in the nuclear fuel cycle. In this work, the microscopic adsorption behaviors of water on the UN(001) surface as well as water dissociation and accompanying H2 formation mechanisms have been investigated on the basis of DFT+U calculations and ab initio atomistic thermodynamics. For adsorption of one H2O monomer, the predicted adsorption energies are -0.88, -2.07, and -2.07 eV for the most stable molecular, partially dissociative, and completely dissociative adsorption, respectively. According to our calculations, a water molecule dissociates into OH and H species via three pathways with small energy barriers of 0.78, 0.72, and 0.85 eV, respectively. With the aid of the neighboring H atom, H2 formation through the reaction of H* + OH* can easily occur via two pathways with energy barriers of 0.61 and 0.36 eV, respectively. The molecular adsorption of water shows a slight coverage dependence on the surface while this dependence becomes obvious for partially dissociative adsorption as the water coverage increases from 1/4 to 1 ML. In addition, based on the "ab initio atomistic thermodynamic" simulations, increasing H2O partial pressure will enhance the stability of the adsorbed system and water coverage, while increasing temperature will decrease the H2O coverage. We found that the UN(001) surface reacts easily with H2O at room temperature, leading to dissolution and corrosion of the UN fuel materials.

15.
Materials (Basel) ; 9(2)2016 Feb 06.
Artigo em Inglês | MEDLINE | ID: mdl-28787902

RESUMO

Nanostructured (NS) materials may have different irradiation resistance from their coarse-grained (CG) counterparts. In this review, we focus on the effect of grain boundaries (GBs)/interfaces on irradiation induced microstructure evolution and the irradiation tolerance of NS materials under irradiation. The features of void denuded zones (VDZs) and the unusual behavior of void formation near GBs/interfaces in metals due to the interactions between GBs/interfaces and irradiation-produced point defects are systematically reviewed. Some experimental results and calculation results show that NS materials have enhanced irradiation resistance, due to their extremely small grain sizes and large volume fractions of GBs/interfaces, which could absorb and annihilate the mobile defects produced during irradiation. However, there is also literature reporting reduced irradiation resistance or even amorphization of NS materials at a lower irradiation dose compared with their bulk counterparts, since the GBs are also characterized by excess energy (compared to that of single crystal materials) which could provide a shift in the total free energy that will lead to the amorphization process. The competition of these two effects leads to the different irradiation tolerance of NS materials. The irradiation-induced grain growth is dominated by irradiation temperature, dose, ion flux, character of GBs/interface and nanoprecipitates, although the decrease of grain sizes under irradiation is also observed in some experiments.

16.
Xi Bao Yu Fen Zi Mian Yi Xue Za Zhi ; 31(6): 740-3, 748, 2015 Jun.
Artigo em Chinês | MEDLINE | ID: mdl-26062413

RESUMO

OBJECTIVE: To observe the dynamic expression and significance of Toll-like receptor 3 (TLR3) in subarachnoid hemorrhage (SAH) model. METHODS: SAH model was established using blood injection into the prechiasmatic cistern. Sixty SD rats were randomly divided into sham group and SAH groups (including SAH 1-, 3-, 7-day groups), each with 15 rats. The operation steps were the same in groups except the sham group that was injected with normal saline instead. At different time points after modeling, the basilar arteries and brain were obtained. The mRNA and protein expression of TLR3 was detected using reverse transcription PCR, Western blotting and immunohistochemistry, respectively. Meanwhile, the distribution of TLR3 was analyzed using the immunofluorescence double labeling technique. RESULTS: The mRNA and protein expression of TLR3 was weak in sham group and highly expressed in SAH groups, and the highest expression were found in SAH 3-day group. Immunohistochemistry showed that TLR3 was highly expressed in vascular endothelial and hippocampal neurons. The sham group showed a weak TLR3 expression in the cytoplasm, while the SHA group showed the strongly expressed TLR3 mainly in the nucleus and cytoplasm. The result of immunofluorescence double labeling also suggested TLR3 was co-localization with CD34 in the endothelial cells. CONCLUSION: The TLR3 expression was enhanced in the basilar arteries and hippocampus when the rats suffered from SAH, which suggested TLR3 might play a certain role in the pathogenesis of SAH.


Assuntos
Artéria Basilar/metabolismo , Regulação da Expressão Gênica , Hipocampo/metabolismo , Hemorragia Subaracnóidea/genética , Hemorragia Subaracnóidea/metabolismo , Receptor 3 Toll-Like/genética , Receptor 3 Toll-Like/metabolismo , Animais , Antígenos CD34/metabolismo , Comportamento Animal , Masculino , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos , Ratos Sprague-Dawley , Transdução de Sinais , Hemorragia Subaracnóidea/patologia
17.
Appl Radiat Isot ; 94: 35-39, 2014 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-25084129

RESUMO

The rate of activation of the isotope (16)O to (16)N in a typical HPLWR one pass concept was calculated using MCNP code. A mathematical model was used to track the inventory of the radioisotope (16)N in a unit mass of coolant traversing the system. The water leaving the moderator channels has the highest activity in the circuit, but due to interaction with fresh coolant at the lower plenum, the activity is downscaled. The calculated core exit activity is higher than values reported in literature for commercial boiling water reactors.

18.
Water Sci Technol ; 67(7): 1642-9, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23552256

RESUMO

Kaolinite/iron oxide magnetic composites (kaolinite/MCs) were used as adsorbent for the removal of Cd(II) from aqueous solutions. The influences of pH, ionic strength, solid/liquid ratio and temperature on Cd(II) sorption on kaolinite/MCs were evaluated. The results showed that the removal of Cd(II) on kaolinite/MCs was strongly dependent on pH and ionic strength. An optimal kaolinite/MCs concentration mass per volume for removal of Cd(II) from aqueous solutions was 1.4 g L(-1). The Langmuir and Freundlich models were used to simulate sorption isotherms of Cd(II) at three different temperatures of 293, 313 and 333 K. The sorption of Cd(II) on kaolinite/MCs increased with increasing temperature, and thermodynamic parameters (standard entropy change, enthalpy change and Gibbs free energy change) illustrated that this sorption process was spontaneous and endothermic. The sorption behaviors of Cd(II) were mainly dependent on surface properties of kaolinite/MCs and solution chemistry conditions. The sorption capacity of Cd(II) on kaolinite/MCs was lower than that on kaolinite, because iron oxide particles decreased surface charge of kaolinite leading to less sorption capacity. Due to high magnetism, kaolinite/MCs could be easily separated with an external magnetic field. Kaolinite/MCs could therefore be used as potential adsorbent for preconcentration and immobilization of Cd(II) ions from large volumes of aqueous solutions.


Assuntos
Cádmio/isolamento & purificação , Compostos Férricos/química , Caulim/química , Eliminação de Resíduos Líquidos , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Concentração de Íons de Hidrogênio , Concentração Osmolar , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura Ambiente , Termodinâmica
19.
Anal Chem ; 85(7): 3715-22, 2013 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-23472747

RESUMO

A rapid and simple method was developed for speciation analysis of (129)I in seawater by selective coprecipitation of carrier-free iodide and accelerator mass spectrometry (AMS) measurement of (129)I. Iodide was separated from seawater and other species of iodine by coprecipitation of AgI with Ag2SO3, AgCl, and AgBr by addition of only 100 mg/L Ag(+) and 0.3 mmol/L NaHSO3 at pH 4.2-5.5. The separation efficiency of iodide was more than 95%, and crossover between (129)IO3(-) and (129)I(-) fractions is less than 3%. Iodate and total inorganic iodine were converted to iodide by use of NaHSO3 at pH 1-2 and then separated by the same method as for iodide. Ag2SO3 in the coprecipitate was removed by washing with 3 mol/L HNO3 and the excess AgCl and AgBr was removed by use of diluted NH3, and finally a 1-3 mg precipitate was obtained for AMS measurement of (129)I. The recovery of iodine species in the entire procedure is higher than 70%. Six seawater samples collected from the Norwegian Sea were analyzed by this method as well as a conventional anion-exchange chromatographic method; the results from the two methods show no significant difference (p = 0.05). Because only one separation step and fewer chemicals are involved in the procedure, this method is suitable for operation on board sampling vessels, as it avoids the transport of samples to the laboratory and storage for a longer time before analysis, therefore significantly improving the analytical capacity and reliability of speciation analysis of (129)I. This improvement can stimulate oceanographic tracer studies of (129)I.

20.
J Environ Radioact ; 118: 30-9, 2013 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-23246587

RESUMO

A method has been developed for speciation analysis of ultra low level (129)I in soil using sequential extraction combined with coprecipitation for separation of carrier free iodine and AMS measurement of (129)I. Two loess profiles collected from northwest China were analyzed for species of (129)I and (127)I. Similar partitioning of (129)I and (127)I was observed in the loess profiles, the distribution of iodine isotopes followed an order of organic > leachable > reducible > residue. The (129)I concentrations and (129)I/(127)I ratios decreased exponentially with the depth, and 2 orders of magnitude lower in the deepest layer (60 and 90 cm) compared with the top layer, indicating a significant contribution of anthropogenic input in the upper layer, and high retention of (129)I in soil. The mobility of (129)I in different fractions decreased in an order of leachable > organic > oxides > residue. The results suggest that migration of iodine downwards in the soil profile is a slow process; the oxides and residue are the less mobile fractions of iodine.


Assuntos
Monitoramento Ambiental/métodos , Radioisótopos do Iodo/análise , Poluentes do Solo/química
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