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1.
Chemosphere ; 244: 125577, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32050350

RESUMO

Persulfate based advanced oxidation process is a promising technology for refractory contaminants removal. Cobalt is considered as the most efficient metal in catalyzing peroxymonosulfate decomposition. Although different cobalt based nanomaterials have been developed, easy aggregation and metal ion leaching during catalytic reaction would result in its deficiency. To address the above issue, in this work, carbon supported Co/CoO core-shell nanocomposite was in-situ fabricated by using polyphenol-metal coordinate as precursor. Results indicated that cobalt nanoparticle with size of 10 nm was successfully prepared and well dispersed within the carbon matrix. By using as-prepared material as catalyst, 50 mg/L orange II was completely removed under the condition of 0.2 g/L peroxymonosulfate, 0.05 g/L catalyst, pH = 4.0-10.0. Both sulfate and hydroxyl radicals were formed during peroxymonosulfate decomposition, while sulfate radical dominated the pollutant removal. Mechanism study revealed that the cobalt was the key site for catalyzing peroxymonosulfate decomposition. This work might provide valuable information in designing and fabricating metal anchored carbon composite catalyst for efficiently and cost-effectively activate peroxymonosulfate.


Assuntos
Corantes/química , Nanocompostos/química , Peróxidos/química , Compostos Azo , Benzenossulfonatos , Carbono/química , Catálise , Cobalto/química , Modelos Químicos , Oxirredução , Sulfatos
2.
Environ Sci Technol ; 54(5): 2985-2993, 2020 03 03.
Artigo em Inglês | MEDLINE | ID: mdl-32072813

RESUMO

Lithium-ion battery demand, particularly for electric vehicles, is projected to increase by over 300% throughout the next decade. With these expected increases in demand, cobalt (Co)-dependent technologies face the risk of significant impact from supply concentration and mining limitations in the short term. Increased extraction and secondary recovery form the basis of modeling scenarios that examine implications on Co supply to 2030. Demand for Co is estimated to range from 235 to 430 ktonnes in 2030. This upper bound on Co demand in 2030 corresponds to 280% of world refinery capacity in 2016. Supply from scheduled and unscheduled production as well as secondary production is estimated to range from 320 to 460 ktonnes. Our analysis suggests the following: (1) Co price will remain relatively stable in the short term, given that this range suggests even a supply surplus, (2) future Co supply will become more diversified geographically and mined more as a byproduct of nickel (Ni) over this period, and (3) for this demand to be met, attention should be paid to sustained investments in refined supply of Co and secondary recovery.


Assuntos
Cobalto , Lítio , Fontes de Energia Elétrica , Mineração , Níquel
3.
Phys Rev Lett ; 124(5): 058101, 2020 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-32083903

RESUMO

We report that trivalent cobalt hexammine cations decrease the persistence length, stretching modulus, helical density, and size of plectonemes formed under torque of DNA but increase those of RNA. Divalent magnesium cations, however, decrease the persistence lengths, contour lengths, and sizes of plectonemes while increasing the helical densities of both DNA and RNA. The experimental results are explained by different binding modes of the cations on DNA and RNA in our all-atom molecular dynamics simulations. The significant variations of the helical densities and structures of DNA and RNA duplexes induced by high-valent cations may affect interactions of the duplexes with proteins.


Assuntos
DNA/química , RNA de Cadeia Dupla/química , Cátions/química , Cobalto/química , Elasticidade , Magnésio/química , Magnetismo/instrumentação , Magnetismo/métodos , Modelos Químicos , Modelos Moleculares , Simulação de Dinâmica Molecular , Pinças Ópticas , RNA/química
4.
Med Lav ; 111(1): 22-31, 2020 Feb 24.
Artigo em Inglês | MEDLINE | ID: mdl-32096770

RESUMO

BACKGROUND: Adverse health effects of occupational exposure to cobalt and its compounds are well-documented. OBJECTIVES: The aim of the study is to evaluate exposures to cobalt in Italian industrial settings. METHODS: Data on cobalt and its compounds were collected from an occupational exposure registry. Statistical analysis was carried out for some exposure-related variables (i.e., cobalt compound, activity sector, occupational group, firm size). The number of workers potentially exposed was estimated for selected industrial sectors. RESULTS: Overall 1,701 measurements were analyzed in the period 1996-2016. The geometric mean of cobalt airborne concentration was 0.33 µg/m3. Most exposures occurred in the manufacture of fabricated metal products (50%) and among metal finishing-, plating- and coating-machine operators (42%). A total of 30,401 workers potentially exposed to cobalt was estimated, over 72% were male. CONCLUSIONS: Identifying professional groups at high-risk of exposure can help to control the most dangerous situations for workers' health. Surveillance systems based on occupational exposure registries contribute to support systematic improvement of working conditions.


Assuntos
Poluentes Ocupacionais do Ar , Cobalto , Exposição Ocupacional , Cobalto/toxicidade , Feminino , Humanos , Indústrias , Itália , Masculino , Exposição Ocupacional/estatística & dados numéricos , Ocupações
5.
Inorg Chem ; 59(3): 2051-2061, 2020 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-31967459

RESUMO

Dioxygen O-O bond activation is a process for oxygenases and oxidases to perform biological functions and synthetic biomimetic catalysts to carry out oxygenation reactions using molecular O2 as an oxidant. Inspired by the experimental development of a CoIII-peroxo complex (i.e., [CoIII(TBDAP)(O2)]+, TBDAP = N,N-ditert-butyl-2,11-diaza[3.3](2,6)-pyridinophane) that exhibits dioxygenase-like reactivity to activate nitriles, a density functional theory (DFT) mechanistic study has been carried out to understand how the peroxo ligand is broken to activate nitriles. The study unveils that the O-O bond cleavage takes place via conversion to a CoII-superoxo complex aided by nitrile coordination, followed by formation of a five-membered intermediate via superoxo O2 radical nucleophilic attack at the nitrile carbon. Finally, a [1,3]-sigmatropic rearrangement-like process breaks the dioxygen bond. The otherwise difficult [1,3]-sigmatropic rearrangement is enabled by the mediation of CoIII(TBDAP) which alters a concerted rearrangement to a sequential process of O-O bond cleavage and N-O bond formation. Expectedly, the unveiling of the O-O bond cleavage mechanism could offer a clue for the development of biomimetic metal oxygenation catalysts.


Assuntos
Quelantes/química , Cobalto/química , Complexos de Coordenação/química , Teoria da Densidade Funcional , Dioxigenases/química , Peróxidos/química , Quelantes/síntese química , Quelantes/metabolismo , Cobalto/metabolismo , Complexos de Coordenação/síntese química , Complexos de Coordenação/metabolismo , Dioxigenases/metabolismo , Modelos Moleculares , Estrutura Molecular , Oxigênio/química , Oxigênio/metabolismo , Peróxidos/metabolismo
6.
Monogr Oral Sci ; 28: 48-58, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31940626

RESUMO

Ultratrace element is a relatively new term, and is defined as those elements with an established, estimated, or suspected dietary requirement of minute amount, generally of the order of µg/day. This chapter focuses on fluorine (F), aluminium (Al), molybdenum (Mo), and cobalt (Co). Whilst diet is the principal source of Al, Mo, and Co found in the body, inadvertent ingestion of dental hygiene products accounts for a significant proportion of F intake. Apart from F, the influence of other ultratrace elements on oral health, and in particular dental caries, has not been fully established. The calcified tissues contain 99% of body F. During tooth development, ingested (systemic) F is incorporated into the apatite crystals of the developing tooth which helps in improving resistance to acid demineralisation. However, the presence of low but constant levels of topical F in the fluid phase at the tooth enamel surface are more important in controlling tooth decay in people of all ages. An adequate intake, from all dietary and non-dietary sources, is estimated as 0.05 mg/kg body weight/day for children older than 6 months and adults, based on estimated intakes that have been shown to reduce the incidence of dental caries while minimising adverse health effects such as dental fluorosis. An inverse relationship between incidence of dental caries and levels of Al in drinking water, food, and soils has been indicated by some epidemiological studies. Co and Mo, whilst occasionally showing potential beneficial oral health effects in laboratory experiments, do so at concentrations much higher than found in vivo.


Assuntos
Cárie Dentária , Molibdênio , Adulto , Alumínio , Criança , Cobalto , Fluoretos , Humanos , Lactente
7.
Chem Commun (Camb) ; 56(13): 1968-1971, 2020 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-31957765

RESUMO

Highly water-soluble cyanocobalamin (also known as vitamin B12) is the most structurally macrocyclic complex comprising cobalt in the center of a corrin ring. Interestingly, it acts as a robust electrocatalyst in water oxidation at ∼0.58 V overpotential with a faradaic efficiency of 97.50% under neutral buffered conditions. The catalyst is impressively stable even after long-term bulk electrolysis, and homogeneous in nature, as established by a series of experiments and characterization techniques.


Assuntos
Vitamina B 12/química , Água/química , Catálise , Cobalto/química , Conformação Molecular , Oxirredução , Potenciometria
8.
Chemosphere ; 241: 125021, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31683448

RESUMO

The magnetic composite CoFe2O4/ZIF-8 based on metal organic framework (MOF) with high specific surface area and high activity was synthesized by solvothermal method. The prepared catalysts were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), vibration sample magnetometer (VSM) and N2 adsorption-desorption isotherms, respectively. After characterization, CoFe2O4/ZIF-8 was applied to heterogeneous activation of peroxymonosulfate (PMS) for degrading methylene blue (MB). The result showed that the 0.075-CoFe2O4/ZIF-8 sample had the excellent catalytic activity. After catalytic reaction for 60 min, the degradation efficiency of MB (20 mg/L) reached about 97.9% at room temperature of 20 °C. The quenching experiment and electron paramagnetic resonance (EPR) analysis indicated that SO4- and OH radicals were the main active species in MB degradation. Meanwhile, the possible MB degradation mechanism was proposed. After four catalytic cycles, the degradation efficiency of MB has not been greatly reduced, indicating the practical application potential of CoFe2O4/ZIF-8 in water pollution cleanup.


Assuntos
Cobalto/química , Corantes/química , Compostos Férricos/química , Estruturas Metalorgânicas/química , Peróxidos/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Adsorção , Catálise , Compostos Férricos/síntese química , Magnetismo , Azul de Metileno/química
9.
Environ Pollut ; 256: 113462, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31706772

RESUMO

Natural birnessite-like minerals are commonly enriched in various transitional metals (TMs), which greatly modify the mineral structure and properties. However few studies are yet conducted systematically on the effects of TM doping on birnessite reactivity towards Cr(III) oxidation. In the present study, the transformation behaviors of Cr(III) on Co-, Ni-, V-containing birnessites were investigated. Co and Ni doping generally decrease the mineral crystalline sizes and hydrodynamic sizes (DH) while V-doping greatly decreases the crystalline sizes but not the DH, owing to particle aggregation. Co and Ni firstly decrease and then increase the mineral zeta potentials (ζ) at pH4 while V decreases ζ. Electrochemical specific capacitances for Co-containing birnessites are gradually reduced, while those for Ni-doped birnessites are slightly reduced and for V-doped birnessites increased, which have a positively linear relationship with the amounts of Cr(III) oxidized by these samples. Cr(III) removal efficiencies from solution by these Co-, Ni- and V-containing birnessites are 26-51%, ∼62-72% and ∼96-100%, respectively, compared to ∼92% by pure birnessite. Cr(III) oxidation kinetics analysis demonstrates the gradual decrease of Mn(IV) and concurrent increase of Mn(III) and the adsorption of mainly Cr(III) on mineral surfaces. A negatively linear relationship exists between birnessite lateral sizes and the proportions of Mn(IV/III) consumed to oxidize Cr(III). Apparent initial Cr(III) oxidation rate (kobs) for Co-containing birnessites are greatly reduced, while those for Ni-doped samples moderately decreased and for V-doped samples first increased and then decreased. A positively or negatively linear relationship exists between kobs or the amount of Mn(II) released and the mineral Mn(IV) content respectively. Cr(III) oxidation probably initiates from layer edge sites of Ni-doped birnessites but the vacancies of Co- and V-containing birnessites. These results provide insights into the reaction mechanisms of Cr(III) with natural birnessite-like minerals.


Assuntos
Óxidos/química , Adsorção , Cromo/química , Cobalto/química , Troca Iônica , Cinética , Minerais , Níquel/química , Oxirredução , Vanádio/química
10.
Waste Manag ; 102: 122-130, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31671359

RESUMO

Some inevitable issues of the acid leaching method used to recycle spent lithium-ion batteries (LIBs), such as toxic gas emission, excessive acid-base consumption, inferior metal selectivity and equipment corrosion, have gradually emerged and restricted the promotion and development of this method. It is therefore essential to develop a sustainable closed-loop recycling technology (reduction-ammoniacal method) for spent LIBs. In this study, the effects of various species of ammonia, ammonium salts and reductants on the leaching of Li, Co, Ni, Mn and Al from spent LIBs were investigated with a hydrothermal method. An increase of the electrode potential of the reductant greatly accelerated the selective leaching of Li, Co and Ni, which agreed with the thermodynamic analysis results. The standard electrode potentials of the LiNixCoyMn1-x-yO2 (NCM) materials were also determined by using approximate calculations. When using (NH4)2SO3 as a reductant in a one-step leaching process, 100% Co, 98.3% Ni and 90.3% Li were extracted into the ammonia-ammonium chloride solutions. From the kinetics analysis, the surface chemical reaction shrinking core model was found to control the leaching behavior of Li, Co, and Ni in the reduction-ammoniacal leaching process. A shell-core structure was composed of a product layer, a diffusion layer of the solid core and an unreacted core. Species in the product layer reduced the leaching efficiencies of Li, Co, and Ni. The results obtained for this hydrothermal reduction-ammoniacal method applied to recycle spent LIBs provide insights for the design of a high-speed, exceptionally selective, closed-loop recycling technique.


Assuntos
Lítio , Níquel , Cobalto , Fontes de Energia Elétrica , Reciclagem , Substâncias Redutoras , Sais
11.
Waste Manag ; 102: 131-138, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31677520

RESUMO

A novel and efficient approach for stepwise recycling of valuable metals from Ni-rich cathode material is developed. First, the spent cathode materials are leached by H2SO4 + H2O2 solution. The leaching efficiencies of lithium, nickel, manganese and cobalt reach almost 100%, 100%, 94% and 100%, respectively, under the conditions of 2 M sulfuric acid, 0.97 M hydrogen peroxide, 10 ml·g-1 liquid-solid ratio, 30 min and 80 °C. Then, manganese and cobalt are co-extracted from the leaching liquor with PC88A, while almost 99% nickel and 100% lithium remain in the raffinate followed by being separated from each other by solvent extraction with neodecanoic acid (Versatic 10). The results show that 98% manganese and over 90% cobalt are co-extracted at pH = 5, 30 vol% PC88A and volume ratio of oil to water (O:A) = 2:1, while 100% nickel is separated from lithium under the optimum extraction conditions of initial pH = 4, O:A = 1:3 and 30 vol% Versatic 10. Finally, cobalt and manganese in the strip liquor of co-extraction are separated by selective precipitation method. Over 90% manganese is separated from cobalt under the conditions of pH = 0.5, 0.076 M KMnO4, 80 °C and 60 min.


Assuntos
Peróxido de Hidrogênio , Lítio , Cobalto , Fontes de Energia Elétrica , Eletrodos , Metais , Reciclagem
12.
Bioresour Technol ; 297: 122385, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31761625

RESUMO

This work mainly studied B. braunii adapted to different CO2 concentrations with cobalt enrichment, and developed a process for CO2 capture, hydrocarbon production and cobalt removal. The results showed that B. braunii favored rapid growth at 5.0% (v/v) CO2, and the highest biomass was 1.89 g.L-1 with 4.5 mg.L-1 of cobalt. Hydrocarbon productivity in high concentration CO2 (5.0% and 10.0%) with cobalt enrichment was higher than that in Chu 13 medium. The change in cobalt removal efficiency mainly corresponded to the growth of B. braunii. The LCE of B. braunii in cobalt-rich with high CO2 concentration (5.0% and 10.0%) was 15.7%, and 14.9%, respectively, which was higher than that in normal medium. CO2 fixation rates were also higher in cobalt enrichment coupled with high CO2 concentration. This study not only provides ideas for the removal of toxic metal cobalt, but also has great potential for CO2 biofixation.


Assuntos
Dióxido de Carbono , Clorófitas , Biomassa , Cobalto , Hidrocarbonetos
13.
Chem Commun (Camb) ; 56(4): 659-662, 2020 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-31840150

RESUMO

Co-based metal organic frameworks (ZIF-67), working as an oxidase-mimicking nanozyme, can simultaneously catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) and Amplex red, exhibiting a high catalytic activity. For Amplex red, two consecutive redox reactions are reported, which is specifically applied for fluorescence "turn-on" detection of biothiols.


Assuntos
Cobalto/química , Fluorescência , Estruturas Metalorgânicas/química , Nanopartículas/química , Oxirredutases/química , Compostos de Sulfidrila/análise , Catálise , Cobalto/metabolismo , Estruturas Metalorgânicas/metabolismo , Estrutura Molecular , Nanopartículas/metabolismo , Oxirredução , Oxirredutases/metabolismo , Tamanho da Partícula , Compostos de Sulfidrila/metabolismo , Propriedades de Superfície
14.
Phys Chem Chem Phys ; 22(3): 985-996, 2020 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-31829369

RESUMO

Owing to their high saturation magnetisation, cobalt nanoparticles hold significant potential for the hyperthermia treatment of tumours. Covalent binding of carboxylic acids to the nanoparticles can induce biocompatibility, whilst also preventing the formation of surface oxides which reduce the magnetic properties of cobalt. Understanding the origin of the acid-metal interaction is key, yet probably the most experimentally challenging step, for the rational design of such entities. In this density functional theory study, we use static calculations to establish that a 57-atom Co cluster is the smallest model able to reproduce the adsorption behaviour of carboxylic acids, and ab initio metadynamics to obtain the structure and the free energy landscape for its interaction with valeric acid. Our simulations show that a bridging bidentate binding mode has a stronger affinity compared to monodentate binding, with energetically high transition barriers between the two. A chelate interaction mode of two carboxyl oxygen atoms can be formed as an intermediate. These results clarify the organic-inorganic interactions in the cobalt-acid system, providing a basis for the rational design of biocompatible metallic nanoparticles.


Assuntos
Ácidos Carboxílicos/química , Ácidos Carboxílicos/metabolismo , Cobalto/química , Nanopartículas Metálicas/química , Adsorção , Materiais Biocompatíveis/química , Simulação por Computador
15.
J Photochem Photobiol B ; 202: 111729, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31835161

RESUMO

Bacterial pathogenicity is becoming a major cause of morbidity and mortality around the globe. Researchers are tirelessly finding solutions to cure or prevent infections caused by bacterial pathogens. Nanotechnology is a fast-growing area of research, effectively influencing and preventing bacterial growth. Nanoparticles (NPs) of silver, copper and gold are being used to kill bacterial pathogens in the past years but the toxicity of NPs at higher concentrations remains a major problem. Therefore, in the present study, Co3O4@ZrO2 (CoZ) core/shell NPs were synthesized using a simple sol-gel method. The synthesized NPs were characterized using different analytical techniques revealing the absorption bands at 456 and 277 nm with crystalline size of ~600 nm core/shell. The functional groups and oxidation states were characterized using FTIR analysis. Further bactericidal properties of core/shell of Co3O4@ZrO2 NPs were tested against Gram negative (Escherichia coli, Pseudomonas aeruginosa) and Gram positive (Staphylococcus aureus, Bacillus subitilis) pathogens. The core/shell CoZ NPs showed maximum growth inhibitions against S. aureus and P. aeruginosa. At the highest concentration of 200 µg/mL, the maximum zone of inhibition was observed. The synthesized CoZ NPs was also subjected to photocatalytic degradation of rhodamine B in 180 min under visible light irradiation. The present study could be an innovative and efficient research for both biomedical and wastewater treatment applications.


Assuntos
Nanopartículas Metálicas/química , Rodaminas/química , Catálise , Cobalto/química , Testes de Sensibilidade a Antimicrobianos por Disco-Difusão , Bactérias Gram-Negativas/efeitos dos fármacos , Bactérias Gram-Positivas/efeitos dos fármacos , Luz , Nanopartículas Metálicas/toxicidade , Óxidos/química , Tamanho da Partícula , Fotólise/efeitos da radiação , Zircônio/química
16.
J Prosthet Dent ; 123(1): 42-44, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31153612

RESUMO

A digital process for designing and manufacturing a cobalt-chromium (Co-Cr) surgical template for static computer-aided implant surgery (s-CAIS) is described. The use of Co-Cr provides the advantage of a material with improved mechanical properties to reduce the possibility of surgical template fracture during s-CAIS. The stronger material also allows for a thinner surgical template, which in turn allows better access when the interarch operative space is limited or a longer implant is inserted. Limitations of the technique include the need for computer-aided manufacturing technology and, with the use of Co-Cr, a higher overall cost.


Assuntos
Cobalto , Implantes Dentários , Cromo , Ligas de Cromo , Projeto Auxiliado por Computador , Planejamento de Prótese Dentária
17.
Chemosphere ; 239: 124743, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31514007

RESUMO

Ethylenediaminetetraacetic acid (EDTA) could form stable complexes with toxic metals such as nickel due to its strong chelation. In this study, with the same doping level of Co and N, MoO2 and ZIF-67 were used as precursors to prepare MoO2@Co/N and FeC@Co/N electrocatalysts for the modified graphite felt cathodes in heterogeneous-electro-Fenton-like reaction (HEFL) system. The X-ray diffraction and X-ray photoelectron spectroscopy results indicated that both of the catalysts are dominated with pyridinic N (2.42% and 2.82%) upon co-doping Co/N, and FeC@Co/N exhibited an obviously higher additional sp-hybridized nitrogen (sp-N) peak. The co-doping of Co/N induced the lattice modifications to produce more lattice defects, where pyridinic N and sp-N, related with the active sites (C-N, Co-Nx), were formed at near-ring defects along sheet edges through the nitrogen replacement of CC groups. FeC@Co/N demonstrated superior oxygen reduction reaction catalytic activity in terms of Cyclic Voltammetry and Rotating Ring-disk Electrode, and exhibited the remarkably higher current density (30 mA) and lower onset potential (-0.208 V) in Linear Sweep Voltammetry analysis. In the FeC@Co/N/CF modified HEFL system, despite the generated H2O2 concentrations (62.5 mg L-1) is not very high, the reducing reaction of ≡Fe(III)/Co(III)-OH could get the electron directly from the cathode, which would greatly reduce the consumption of H2O2, high utilization efficiency of H2O2 (η: 87.63%) could greatly improve the EDTA-Ni removal (97.5%) and TOC (92.6%). This work demonstrates the feasibility of utilizing FeC@Co/N/CF as a cathode for breaking metal-complex in HEFL process.


Assuntos
Cobalto/química , Ácido Edético/química , Técnicas Eletroquímicas/métodos , Nanopartículas Metálicas/química , Níquel/química , Catálise , Descontaminação , Técnicas Eletroquímicas/instrumentação , Eletrodos , Grafite/química , Peróxido de Hidrogênio/química , Ferro/química , Nitrogênio/química , Oxirredução , Piridinas/química , Eliminação de Resíduos Líquidos/instrumentação , Eliminação de Resíduos Líquidos/métodos
18.
Talanta ; 207: 120284, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31594616

RESUMO

Magnetic carbon nanotubes (CNTs) with encapsulated Co nanoparticles (Co@CNTs), was synthesized by exploiting the one-step pyrolysis strategy using ZIF-67 as template. The as-synthesized Co@CNTs is provided with the nanopores, a large specific surface area, and strong magnetic response. The obtained Co@CNTs was used as magnetic solid-phase extraction adsorbents to extract two profens including flurbiprofen and ketoprofen. The parameters of extraction efficiency, involving extraction time, sample solution volume, ionic strength, pH and the conditions of desorption efficiency, were optimized in detail. After determined by high-performance liquid chromatography-ultraviolet (HPLC-UV), the results evinced that Co@CNTs showed a high extraction efficiency with high enrichment factors of 832 and 672. The good linear range of both flurbiprofen and ketoprofen were all 5.0-1000 ng L-1, with the limit of detection were 0.60 ng L-1 and 0.70 ng L-1, respectively. Furthermore, a valid method for the extraction of flurbiprofen and ketoprofen from human serum was established. The spiking recoveries of two profens were between 86.74% and 97.22%, and the relative standard deviation was less than 6.55%. Co@CNTs can be repeatedly used at least 10 times, indicating its excellent regeneration and reusability. The results demonstrated that the Co@CNTs materials exhibits high enrichment ability and extraction efficiency, playing great promise in MSPE.


Assuntos
Flurbiprofeno/isolamento & purificação , Cetoprofeno/isolamento & purificação , Imãs/química , Nanotubos de Carbono/química , Compostos Organometálicos/química , Extração em Fase Sólida/métodos , Adsorção , Cobalto/química , Flurbiprofeno/sangue , Flurbiprofeno/química , Humanos , Imidazóis/química , Cetoprofeno/sangue , Cetoprofeno/química , Nanopartículas Metálicas/química
19.
Biochim Biophys Acta Bioenerg ; 1861(1): 148118, 2020 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-31734195

RESUMO

CO dehydrogenase (CODH) from the Gram-negative bacterium Oligotropha carboxidovorans is a complex metalloenzyme from the xanthine oxidase family of molybdenum-containing enzymes, bearing a unique binuclear Mo-S-Cu active site in addition to two [2Fe-2S] clusters (FeSI and FeSII) and one equivalent of FAD. CODH catalyzes the oxidation of CO to CO2 with the concomitant introduction of reducing equivalents into the quinone pool, thus enabling the organism to utilize CO as sole source of both carbon and energy. Using a variety of EPR monitored redox titrations and spectroelectrochemistry, we report the redox potentials of CO dehydrogenase at pH 7.2 namely MoVI/V, MoV/IV, FeSI2+/+, FeSII2+/+, FAD/FADH and FADH/FADH-. These potentials are systematically higher than the corresponding potentials seen for other members of the xanthine oxidase family of Mo enzymes, and are in line with CODH utilising the higher potential quinone pool as an electron acceptor instead of pyridine nucleotides. CODH is also active when immobilised on a modified Au working electrode as demonstrated by cyclic voltammetry in the presence of CO.


Assuntos
Aldeído Oxirredutases/química , Bradyrhizobiaceae/enzimologia , Metaloproteínas/química , Complexos Multienzimáticos/química , Aldeído Oxirredutases/metabolismo , Catálise , Domínio Catalítico , Cobalto/química , Cobalto/metabolismo , Espectroscopia de Ressonância de Spin Eletrônica , Flavina-Adenina Dinucleotídeo/química , Flavina-Adenina Dinucleotídeo/metabolismo , Metaloproteínas/metabolismo , Molibdênio/química , Molibdênio/metabolismo , Complexos Multienzimáticos/metabolismo
20.
Food Chem ; 302: 125336, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31419772

RESUMO

This study reports a stepwise optimization of switchable liquid-liquid microextraction (SLLME) for cobalt determination by flame atomic absorption spectrometry (FAAS) coupled with a slotted quartz tube (SQT). The main purpose of this study was to develop an accurate and sensitive analytical method for cobalt. Extraction method was used to separate and preconcentrate cobalt from sage tea and vitamin B12 samples after complexing with a Schiff base ligand. 107.7 folds enhancement in detection power under the optimum conditions was recorded with respect to direct FAAS. This enhancement correlated to 3.1 µg/L limit of detection and 10 µg/L limit of quantification. The SLLME-SQT-FAAS method was linear over a broad concentration range and low %RSD values established high precision for the method. Appreciable percent recovery results (94-108%) obtained from spiked sage sample and from cobalamin also validated the accuracy of the method.


Assuntos
Cobalto/análise , Microextração em Fase Líquida/métodos , Espectrofotometria Atômica/métodos , Chás de Ervas/análise , Vitamina B 12/análise , Limite de Detecção , Quartzo , Reprodutibilidade dos Testes , Salvia officinalis/química , Bases de Schiff/química , Espectrofotometria Atômica/instrumentação , Vitamina B 12/química
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