Selective Sorbent Enrichment of Nickel Ions from Aqueous Solutions using a Hierarchically Hybrid Organic-Inorganic Polymer Based on Double Imprinting Concept

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)This study involves the preparation of an ion imprinted organic-inorganic polymer (IIP) for selective sorbent enrichment of Ni(2+) from aqueous solutions with further determination by GF AAS. The hybrid polymeric network was prepared from a mixture of 2-aminoethyl-3-aminobutylmethyldimethoxysilane as functional monomer, and tetraethoxysilane as crosslinking agent, containing Ni(2+) and cetyltrimethylammonium bromide as templates. The polymers were characterized by IR, TG and SEM. The maximum adsorptive capacity of IIP towards Ni(2+) ions, determined by linear Langmuir model, was found to be 5.44 mg g(-1). When the selectivity coefficient of IIP was compared with the selectivity coefficient of NIP (non imprinted polymer) and IIP2 (ion imprinted polymer in the absence of surfactant), from the binary mixtures of Ni(2+)/Cu(2+), Ni(2+)/Co(2+), Ni(2+)/Cd(2+) and Ni(2+)/Zn(2+), values of relative selectivity coefficient (k') were 36.54 and 3.55, 1.22 and 2.03, 4.43 and 1.42, 28.60 and 1.74, respectively, demonstrating higher selectivity of IIP for Ni(2+) ions. The proposed method provided a limit of detection of 0.16 mu g L(-1) and was successfully applied for Ni(2+) determination in spiked water samples and in a phytoterapic product (Gingko Biloba) with satisfactory recovery values.213419430Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)INCT of Bioanalytical (Instituto Nacional de Ciencia e Tecnologia de Bioanalitica)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

EMPLOY OF SILICA GEL ORGANICALLY MODIFIED AND IONICALLY IMPRINTED FOR SELECTIVE ON-LINE PRECONCENTRATION OF COPPER IONS

EMPLOY OF SILICA GEL ORGANICALLY MODIFIED AND IONICALLY IMPRINTED FOR SELECTIVE ON-LINE PRECONCENTRATION OF COPPER IONS. The present work purposes the preparation of a silica gel sorbent organically modified with 2-aminoethyl-3-aminobutylmethyldimethoxysilane (AAMDMS) and imprinted with Cu(2+) ions by means surface imprinting technique and its use for selective on-line sorbent preconcentration of Cull ions with further UV-VIS spectrophotometric determination by flow injection analysis. The Cu(2+)-imprinted silica gel, when compared with non imprinted silica gel and silica gel, showed from the binary mixture Of Cu(2+)/Ni(2+) relative selectivity coefficient (k') of 6.84 and 5.43 and 6.64 and 19.83 for the mixture Cu(2+)/Pb(2+), thus demonstrating higher selectivity of Cu(2+)-imprinted silica gel towards Cull ions. Under optimized condition, the on-fine preconcentration method provided detection limit of 3.4 mu g L(-1) and linear range ranging from 30.0 up to 300.0 mu g L(-1) (r = 0.995). The accuracy of method was successfully assessed by analyzing different kind of spiked water samples with recovery values ranging from 92.2 up to 103.0%.33230130

Highly improved sensitivity of TS-FF-AAS for Cd(II) determination at ng L-1 levels using a simple flow injection minicolumn preconcentration system with multiwall carbon nanotubes

A new method for cadmium determination at ng L-1 levels is described. The method is based on the on-line coupling of a flow preconcentration system using multiwall carbon nanotubes (MWCNT) as sorbent with TS-FF-AAS determination. Cadmium preconcentration was at pH 4.9 onto an MWCNT minicolumn (30 mg) for 2 min at a 5.0 mL min(-1) flow rate. The elution step is performed by using 0.5 mol L-1 HNO3 and the cadmium desorbed is directly pumped to a TS-FF-AAS. All experimental parameters that play important roles in system performance were evaluated and optimized by means of fractional factorial designs and response surface methodology. The excellent characteristics of MWCNT as sorbent, mainly owing to its high surface area, make it possible to obtain a preconcentration factor of 51-fold, thus improving the detection and quanti. cation limits in TS-FF-AAS, 11.4 and 38.1 ng L-1, respectively. When the flow preconcentration system, FI-TS-FF-AAS, was compared with FAAS alone, an increase in the sensitivity of 640-fold was obtained. The calibration graph was linear with a correlation coefficent higher than 0.999 from 38.1 to 1250 ng L-1. Repeatability of the measurements (n = 10), assessed as relative standard deviation (RSD), was found to be 6.5 and 2.1% for cadmium concentrations of 100 and 1000 ng L-1, respectively. Important parameters to characterize the flow preconcentration system were also evaluated, the consumption index being 0.196 mL, the concentration efficiency 25.5 min(-1) and the sample throughput 20 samples per hour. In order to demonstrate the accuracy of the system, addition and recovery studies in water samples (mineral water, tap water and river water) and cigarette samples were carried out. Moreover, for the same purpose, cadmium was determined in certified biological materials (Bovine Liver and Rye Grass), giving an average result in close agreement with the certified value.21111305131

A New and Fast Technique to Generate Offspring after Germ Cells Transplantation in Adult Fish: The Nile Tilapia (Oreochromis niloticus) Model

Background: Germ cell transplantation results in fertile recipients and is the only available approach to functionally investigate the spermatogonial stem cell biology in mammals and probably in other vertebrates. In the current study, we describe a novel non-surgical methodology for efficient spermatogonial transplantation into the testes of adult tilapia (O. niloticus), in which endogenous spermatogenesis had been depleted with the cytostatic drug busulfan. Methodology/Principal Findings: Using two different tilapia strains, the production of fertile spermatozoa with donor characteristics was demonstrated in adult recipient, which also sired progeny with the donor genotype. Also, after cryopreservation tilapia spermatogonial cells were able to differentiate to spermatozoa in the testes of recipient fishes. These findings indicate that injecting germ cells directly into adult testis facilitates and enable fast generation of donor spermatogenesis and offspring compared to previously described methods. Conclusion: Therefore, a new suitable methodology for biotechnological investigations in aquaculture was established, with a high potential to improve the production of commercially valuable fish, generate transgenic animals and preserv

Synthesis and structural characterization of carbon-rich SiCxOy derived from a Ni-containing hybrid polymer

Carbon-rich silicon oxycarbide ceramics were obtained by controlled pyrolysis at 950, 1300 and 1500 degrees C from hybrid polymeric precursors based on poly(methylsiloxane) and divinylbenzene with different molar ratios, in the presence or absence of nickel acetate. By increasing the pyrolysis temperature changes in the local molecular structure were observed by Si-29 NMR, with the segregation of thermodynamically stable SiO2 and SiC phases, in addition to formation of graphitic carbon nanoclusters. Ceramics without Ni were amorphous at 950 degrees C, while those obtained at 1300 degrees C showed the presence of a beta-SiC phase. The presence of Ni in the polymeric precursor induced the formation of beta-SiC, cristobalite silica, graphitic carbon, metallic Ni, NiO and Ni2Si, and also reflected in denser materials. In general, the resulting ceramics without Ni did not present measurable porosity, whereas Ni-containing ceramics at 1500 degrees C showed behavior typical of mesoporous materials. (C) 2008 Elsevier Ltd. All rights reserved.28112247225

Synthesis and adsorption studies of novel hybrid mesoporous copolymer functionalized with protoporphyrin for batch and on-line solid-phase extraction of Cd2+ ions

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)A hybrid copolymer [poly(ethylene glycol dimethacrylate-co-protoporphyrin)-silica], synthesized by free radical copolymerization and sol-gel process was evaluated as novel adsorbent for solid-phase extraction of Cd2+ ions. Characterization of hybrid polymer was performed by FUR, SEM and surface area analyzes. Adsorption isotherms built at pH 8.9 were very well adjusted (R-2 = 0.9982) to hybrid non-linear Langmuir-Freundlich model for two sites, indicating the existence of different affinity constants for binding sites, which was confirmed by Scatchard plot. The estimated maximum adsorption capacity was found to be 8.28 mg g(-1). The adsorption kinetics data also corroborated to the isotherm, where the Cd2+ ions adsorption followed the pseudo-second-order kinetic (R-2 = 0.998). The on-line preconcentration procedure, optimized by means of factorial designs, was based on sample preconcentration (16 mL) at pH 8.9 through 50.0 mg of hybrid copolymer packed in mini-column at 8.0 mL min flow rate. The on-line desorption of Cd2+ ions towards the FAAS detector was carried out in countercurrent at 5.0 mL min(-1) flow rate using 0.8 mol L-1 HNO3. Using the on-line preconcentration procedure, the maximum adsorption capacity determined from breakthrough curve was found to be 2.25 mg g(-1). Analytical curve ranged from 0.0 up to 50.0 mu g L-1 (r = 0.997), limit of detection of 0.27 mu g L-1, preconcentration factor of 38.4, sample throughput of 30 h(-1) and consumptive index of 0.41 mL, were achieved. The preconcentration method, very tolerable to several foreign ions, was successfully applied to the Cd2+ ions determination in water samples and cigarette sample. The accuracy was checked from analysis of certified reference materials. (C) 2013 Elsevier Ltd. All rights reserved.736838846Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Instituto Nacional de Ciencia e Tecnologia de Bioanalitica (INCT) [573672/2008-3]Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)CNPq [471655/2011-2, 308580/2010-9, 471912/2011-5]Instituto Nacional de Ciencia e Tecnologia de Bioanalitica (INCT) [573672/2008-3

Natural silica fiber as reinforcing filler of nylon 6

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Short silica fiber (SF) content on the mechanical and morphological proper-ties of composites based on nylon 6 and rubber-toughened nylon 6 matrices was examined Binary nylon 6/SF and ternary I nylon 6/EPDM-g-MA (ethylene-propylene-diene grafted with maleic anhydride)/SF] composites containing 0-20 wt% SF were formulated. The flexural modulus increased with the SF content at all fiber compositions investigated: however, the value of this property gradually diminished when 20 wt% rubber was added to the polymer. Notched Izod impact strength of 80120 nylon 6/EPDM-g-MA blend was reduced up to 50% with the addition of 5 wt% SF. However. these composites still retained good stiffness and toughness and presented a good interfacial adhesion between the phases. The results suggest that silica fibers can be employed as an alternative reinforcement of nylon 6 matrices, resulting in materials with useful properties (C) 2009 Elsevier Ltd. All rights reserved41198105Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Amperometric determination of chloroguaiacol at submicromolar levels after on-line preconcentration with molecularly imprinted polymers

In this study, a sorbent flow preconcentration system coupled to amperometric detector for the chloroguaiacol (4-chloro-2-methoxyphenol) determination at submicromolar levels is described. The satisfactory selectivity of the proposed method was attained by means of the use of a chloroguaiacol-imprinted polymer, whose the synthesis was carried out by bulk polymerization. Flow and chemical parameters associated to the preconcentration system, such as sample pH, preconcentration and elution flow rates, concentration of the carrier solution (KCl) and eluent volume were investigated through multivariate analysis. The flow preconcentration of chloroguaiacol was not affect by equimolar presence of structurally similar phenolic compounds including catechol, 4-chloro-3-methylphenol, 4-aminophenol and 2-cresol, thus showing the good performance of the imprinted polymer. Under the best experimental conditions, it was obtained a preconcentration factor of 110-fold and low detection and quantification limits of 27 and 78 nmol L-1, respectively. The analytical curve covered a wide linear range from 0.05 up to 5.0 mu mol L-1 (r > 0.999) and satisfactory precision (n = 8) evaluated by relative standard deviation (R.S.D.) were respectively, 5.5 and 4.2%, for solutions of 1.0 and 5.0 mu mol L-1 chloroguaiacol. Other parameters related to the performance of the flow system were also evaluated including concentration efficiency of 27.5 min(-1) and consumptive index of 0.09 mL. Recoveries varying from 93 up to 112% for water samples (tap water and river water) spiked with chloroguaiacol concentration were achieved, thus assuring the accuracy of the proposed flow preconcentration system. (c) 2005 Elsevier B.V. All rights reserved.69125926