Home About us Contact
|
Home About us Contact | ||
|
|
||
NaOH
Kinds of NaOH Terms modified by NaOH Selected AbstractsInfluence of Metal Nanoparticles on the Electrocatalytic Oxidation of Glucose by Poly(NiIIteta) Modified ElectrodesELECTROANALYSIS, Issue 5 2010Pratap Azad Abstract Conductive polymeric [NiII(teta)]2+ (teta=C-meso-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetra-azacyclotetradecane) films (poly(Ni)) have been deposited on the surface of glassy carbon (GC), Nafion (Nf) modified GC (GC/Nf) and Nf stabilized Ag and Au nanoparticles (NPs) modified GC (GC/Ag-Nf and GC/Au-Nf) electrodes. The cyclic voltammogram of the resulting electrodes, show a well defined redox peak due to oxidation and reduction of poly(Ni) system in 0.1,M NaOH. They show electrocatalytic activity towards the oxidation of glucose. AFM studies reveal the formation of poly(Ni) film on the modified electrodes. Presence of metal NPs increases electron transfer rate and electrocatalytic oxidation current by improving the communication within the Nf and poly(Ni) films. In the presence of metal NPs, 4 fold increase in current for glucose oxidation was observed. [source] Catalytic Effect on Silver Electrodeposition of Gold Deposited on Carbon ElectrodesELECTROANALYSIS, Issue 19 2004Alfredo de, Escosura-Muñiz Abstract A new methodology, based on silver electrocatalytic deposition and designed to quantify gold deposited onto carbon paste electrode (CPE) and glassy carbon electrode (GCE), has been developed in this work. Silver (prepared in 1.0,M NH3) electrodeposition at ,0.13,V occurs only when gold is previously deposited at an adequate potential on the electrode surface for a fixed period of time. When a CPE is used as working electrode, an adequate oxidation of gold is necessary. This oxidation is carried out in both 0.1,M NaOH and 0.1,M H2SO4 at oxidation potentials. When a GCE is used as working electrode, the oxidation steps are not necessary. Moreover, a cleaning step in KCN, which removes gold from electrode surface, is included. To obtain reproducibility in the analytical signal, the surface of the electrodes must be suitably pretreated; this electrodic pretreatment depends on the kind of electrode used as working electrode. Low detection limits (5.0×10,10,M) for short gold deposition times (10,min for CPE and 5,min for GCE) were achieved with this novel methodology. Finally, sodium aurothiomalate can be quantified using silver electrocatalytic deposition and GCE as working electrode. Good linear relationship between silver anodic stripping peak and aurothiomalate concentration was found from 5.0×10,10,M to 1.0×10,8,M. [source] Electrochemical Overoxidation of Polyindole and Its Cation-Permselective BehaviorELECTROANALYSIS, Issue 12 2004Mihaela Ghita Abstract Polyindole films prepared by potentiostatic growth in dichloromethane solution were subjected to overoxidation studies in aqueous media. Overoxidation at potentials greater than 1.1,V (vs. SCE) in 0.1,M KNO3 or 0.1,M H2SO4 was possible. Overoxidation in 0.1,M NaOH resulted in mechanically unstable films which were not adherent to the electrode surface. The overoxidation process in 0.1,M KNO3 involved removal of one electron per four indole monomer moieties in the polymer film. Nucleophilic attack led to introduction of carboxylate functionality and to cation permselective behavior, as tested by cyclic voltammetry and hydrodynamic voltammetry of hexamminoruthenium(III) and hexacyanoferrate(III). Such films may be useful in various electrochemical sensor applications. [source] Multiple-point electrochemical detection for a dual-channel hybrid PDMS-glass microchip electrophoresis deviceELECTROPHORESIS, Issue 19 2009Mario Castaño-Álvarez Abstract A new PDMS-based dual-channel MCE with multiple-point amperometric detection has been evaluated. Electrophoresis has been optimised in a single-channel device. Pretreatment with 0.1,M NaOH is very important for increasing and stabilising the EOF. The precision is adequate for a day's work in terms of both peak current and migration time. The RSD of the peak current for five successive signals was 1.9, 2.4 and 3.1% for dopamine, p- aminophenol and hydroquinone. RSD for the migration time was always less than 1.3%, which demonstrates the stability of the EOF and the possibility of running multiple experiments in the same microchip. The adequate inter-microchip precision as well as the rapid and simple manufacturing procedure indicates the disposable nature of the PDMS microchips. A dual-channel device with very simple multiple-point amperometric detection is proposed here. Elasticity of the PDMS allows removing the polymer slightly and aligning gold wires working electrodes. Injection can be performed from each of the sample reservoirs or from both simultaneously. The distance between the separation channels is critical for obtaining adequate signals as well as the introduction of a high-voltage electrode in the buffer reservoir. Simultaneous measurement of the same analytes in both channels is possible by applying the same potential. Moreover, since no cross-separation is produced, different analytes or samples can be simultaneously measured. [source] Direct chiral analysis of primary amine drugs in human urine by single drop microextraction in-line coupled to CEELECTROPHORESIS, Issue 16 2009Kihwan Choi Abstract Three-phase single drop microextraction (SDME) was in-line coupled to chiral CE of weakly basic amine compounds including amphetamine. SDME was used for the matrix isolation and sample preconcentration in order to directly analyze urine samples with the minimal pretreatment of adding NaOH. A small drop of an acidic aqueous acceptor phase covered with a thin layer of octanol was formed at the tip of a capillary by simple manipulation of the liquid handling functions of a commercial CE instrument. While the saline matrix of the urine sample was blocked by the octanol layer, the basic analytes in a basic aqueous donor phase were concentrated into the acidic acceptor drop through the octanol layer by the driving force of the pH difference between the two aqueous phases. The enantiomers of the enriched amines were resolved by using (+)-(18-crown-6)-tetracarboxylic acid as a chiral selector for the subsequent CE separation. From 10,min SDME with the agitation of the donor phase by a small stirrer retrofit to the CE instrument, enrichment factors were about a 1000-fold, yielding the LOD of 0.5,ng/mL for amphetamine. This low LOD value as well as the convenience of in-line coupled SDME make the proposed scheme well suited for the demanding chiral analysis of amphetamine-type stimulants. [source] CE with electrochemical detection for investigation of label-free recognition of amino acid amides by guanine-rich DNA aptamersELECTROPHORESIS, Issue 17 2007Tao Li Abstract In this work, we report a simple and effective investigation into adaptive interactions between guanine-rich DNA aptamers and amino acid amides by CE with electrochemical (EC) detection. Argininamide (Arm) and tyrosinamide (Tym) were chosen as model molecules. On a copper electrode, Arm generated a good EC signal in 60 mM NaOH at 0.7 V (vs Ag/AgCl), while Tym was detected well on a platinum electrode at 1.3 V in 20 mM phosphate of pH 7.0. Based on their EC properties, the ligands themselves were used as indicators for the adaptive interactions investigated by CE-EC, making any step of labeling and/or modification of aptamers with indicators exempted. Hydrophilic ionic liquid was used as an additive in running buffer of CE to improve the sensitivity of Arm detection, whereas the additive was not used for Tym detection due to its negative effect. Two guanine-rich DNA aptamers were used for molecular recognition of Arm and Tym. When the aptamers were incubated with ligands, they bound the model molecules with high affinity and specificity, reflected by obvious decreases in the signals of ligands but no changes in those of the control molecules. However, the ligands were hardly affected by the control ssDNAs after incubation. The results revealed the specific recognition of Arm and Tym by the aptamers. The mechanisms for binding model molecules by aptamers were discussed. Not as expected, these aptamers were not to form the G-quartets, which were generally responsible for binding the ligands when the guanine-rich aptamers were used. [source] Determination of xanthohumol in hops (Humulus lupulus L.) by nonaqueous CEELECTROPHORESIS, Issue 6 2007Javor Kac Dr. Abstract Xanthohumol (XN) is a prenylated chalcone with antimutagenic and anticancer activity from hops. A nonaqueous reverse polarity capillary electrophoretic method for the determination of XN in hop extract was developed and validated. The optimal parameters were a 64.5,cm long fused-silica capillary with 50,,m id at 25°C; 30,kV negative voltage (anode at detector side of the capillary); nonaqueous buffer with 75,mM NaOH and 50,mM boric acid in methanol; hydrodynamical injection with 10,mbar for 40,s; and detection at 440,nm. XN, isoxanthohumol (IX), colupulone, adlupulone, and n -lupulone were well resolved on the electropherogram. The LOD for XN was 0.05,mg/L and RSD for peak area was below 3%. The amount of XN in different samples of hop pellets varied from 0.14 to 0.42%. [source] Effect of alkali metal hydroxides on the enantioseparation of amines using di- O -isopropylidene-keto- L -gulonic acid as the selector in NACEELECTROPHORESIS, Issue 22 2006Ylva Hedeland Dr. Abstract The present work demonstrates the importance of the ionic composition in the BGE for enantioseparation. (,)-2,3:4,6-di- O -Isopropylidene-2-keto- L -gulonic acid ((,)-DIKGA) has been used as the chiral selector in methanolic and ethanolic BGEs. The influence of added alkali metal hydroxides on the EOF and the chiral separation of amines (atenolol, isoprenaline, pindolol and propranolol) have been studied. The ion-pair formation constants in ethanol were determined by precision conductometry for the enantiomers of pindolol with (,)-DIKGA, for Li+, Na+ and Cs+ with (,)-DIKGA, and also for the corresponding alkali metal hydroxides. The effective mobilities and the enantiomeric mobility differences were affected by the type of alkali metal hydroxide (LiOH, NaOH, KOH, RbOH or CsOH) added to the BGE. The effective mobility and mobility difference were increased with decrease in solvated radius of the alkali metal cation. These differences could partly be correlated to the ion-pair formation constants of the alkali metal cations with the chiral selector, affecting the equilibrium concentration of the free selector. The electroosmosis was also affected by the alkali metal hydroxide added to the BGE. The cathodic electroosmosis decreased with decreasing solvated radius of the alkali metal cation added to the BGE. Interestingly, the cathodic EOF was even reversed, i.e. became anodic in the ethanolic BGEs containing KOH, RbOH or CsOH and the methanolic ones with RbOH and CsOH. [source] High-efficiency protein extraction from polyacrylamide gels for molecular mass measurement by matrix-assisted laser desorption/ionization-time of flight-mass spectrometryELECTROPHORESIS, Issue 6 2005Ya Jin Abstract A simple and fast method of protein extraction from Coomassie Brilliant Blue (CBB)-stained polyacrylamide gels suited for molecular mass measurement of proteins by matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS) is reported. Proteins in CBB-stained gel pieces were extracted by a 10-min soaking in 0.1,M NaOH at 25°C. The recovery of this one-step extraction method was 34,73% for proteins <67,kDa. CBB adduction to proteins during mass spectrometric analysis was avoided by a destaining step before the alkaline extraction. The molecular mass values of the extracted proteins coincided with those of purified proteins within ±0.01,0.10% deviation for all the proteins <36,kDa. Because of the high extraction recovery, mass measurement was possible for the proteins extracted from CBB-stained gels with loaded protein quantities as little as 34,ng for cytochrome,c, ,-lactalbumin, myoglobin, ,-lactoglobulin, trypsinogen, and carbonic anhydrase (12.4,29.0,kDa), 340,ng for glyceraldehyde-3-phosphate dehydrogenase (35.6,kDa) and albumin (66.3,kDa). This method provides a highly efficient approach to utilize CBB-stained one- or two-dimensional gels for whole protein analysis using MALDI-TOF-MS. [source] Absorption of H2S in NaOCl caustic aqueous solutionENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 3 2001Luke Chen Pilot plant experimental data were collected to study the feasibility of H2S removal from air streams utilizing aqueous solutions. Solutions of NaOCl/NaOH were tested in a packed bed scrubber and found to be effective. An efficiency of 99.2% H2S removal was achieved at a gas flow rate of 790 lb/f2 -hr and liquid-gas ratio of 5.06. Sodium hydroxide was found to be the active ingredient in the absorption process. A minimum alkalinity of pH 11 in the scrubbing solution was required for the H2S to be efficiently absorbed in the packed bed scrubber. For gas flow rates up to 2,100 lb/f2 hr, the height of a transfer unit (HTU) varied from 1.8 ft to 2 ft with different proportions of NaOCl and NaOH in the solution. [source] Slow desorption behavior of one highly resistant aromatic amine in Lake Macatawa, Michigan, USA, sedimentENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2005Shihua Chen Abstract The desorption behavior of benzidine from Lake Macatawa (Holland, MI, USA) sediment was investigated in this study using batch solvent extraction method. Seven solvents were tested as the extracting reagents: Deionized water (DI), calcium chloride in DI (CaCl2), sodium hydroxide in DI (NaOH), acetonitrile (ACN), a mixture of acetonitrile and ammonium acetate in DI (ACNNH4OAc), methanol (MeOH), and hydrochloric acid in DI (HCl). These solvents are proposed to react with sediment-associated benzidine by different mechanisms (e.g., cation exchange, hydrophobic partitioning, and covalent binding). Three sets of sorption isotherm experiments were conducted separately in these seven solvents with a 7-d, three-week, and two-month contact time. The results demonstrated nonlinear isotherms with Freundlich 1/n values varying from 0.25 to 0.52. The desorption behavior of benzidine in the solvents was evaluated after the sorption of benzidine onto the sediment with same contact times of 7 d, three weeks, and two months. A two-stage model subsequently was applied to simulate the experimental data. The rapidly desorbing rate constants were on the order of one to two per day for ACN, ACN-NH4OAc, and NaOH solvents, and the slowly desorbing rate constants were on the order of 10,5 to 10,4/d. Sequential desorption experiment demonstrated low total extraction efficiency of less than 40%. Both the observed sorption and desorption phenomena suggested that hysteresis and/or mass-transfer limited diffusion may result in the slow desorption behavior observed in this study. [source] Facile and Reproducible Synthesis of Nanostructured Colloidal ZnO Nanoparticles from Zinc Acetylacetonate: Effect of Experimental Parameters and Mechanistic InvestigationsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 33 2009Alessia Famengo Abstract A facile and reproducible route to nanostructured colloidal ZnO nanoparticles was developed by controlled hydrolysis and condensation of zinc acetylacetonate in alkaline conditions. By reaction of an ethanolic solution of Zn(acac)2 with NaOH in a 1:2 molar ratio, after reflux, ZnO spherical nanoparticles were obtained that displayed a homogeneous size distribution; particle diameters ranged from 6 to 10 nm, as evidenced by transmission electron microscopy (TEM) analysis. The same reaction was carried out also in water, glycerol and 1,2-propanediol, to investigate the effect of the solvent viscosity and dielectric constant on the final features of the obtained material. Irrespective of the nature of the solvent, X-ray diffraction (XRD) analysis shows the formation ofhexagonal ZnO, whereas the presence of residual unreacted Zn(acac)2 could be ruled out. Indeed, different particle sizes and very different morphologies were obtained. Also the reflux step was shown to be a key factor in avoiding the fast precipitation of a floc and achieving a pure compound, which was isolated and thoroughly characterised. The composition of the obtained ZnO was determined by elemental analysis, X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA), showing the formation of pure ZnO. IR spectroscopy evidenced the presence of adsorbed organic ligands on the colloid surfaces. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) revealed the presence of medium- to high-strength acidic sites on the ZnO surface. To gain a deeper insight into the formation mechanisms of these nanostructures, time-resolved UV/Vis and XAS studies were performed on the ethanol solution used for the synthesis of the oxide and also on the solid specimen, obtained after the refluxing step. No remarkable changes could be evidenced in the solution after the addition of an understoichiometric amount of NaOH, but the growth of the ZnO nanoparticles could be followed by UV/Vis spectra. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Fluoride-Free Hiyama and Copper- and Amine-Free Sonogashira Coupling in Air in a Mixed Aqueous Medium by a Series of PEPPSI-Themed Precatalysts,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2009Chandrakanta Dash Abstract A new series of robust, user-friendly, and highly active PEPPSI-themed (pyridine-enhanced precatalyst preparation, stabilization and initiation) (NHC)PdX2(pyridine)-type (X = Cl, Br) precatalysts of C4,C5 saturated imidazole- (1,4) and triazole-based (5 and 6) N-heterocyclic carbenes for the Hiyama and Sonogashira couplings under amenable conditions are reported. Specifically 1,6 efficiently catalyze the fluoride-free Hiyama coupling of aryl halides with PhSi(OMe)3 and CH2=CHSi(OMe)3 in air in the presence of NaOH as a base in a mixed aqueous medium (dioxane/H2O, 2:1 v/v). Along the same lines, these 1,6 precatalysts also promote the Cu-free and amine-free Sonogashira coupling of aryl bromides and iodides with phenylacetylene in air and in a mixed aqueous medium (DMF/H2O, 3/1 v/v). The complexes 1,6 were synthesized by the direct reaction of the respective imidazolinium and triazolium halide salts with PdCl2 in pyridine in the presence of K2CO3 as a base. DFT studies on the catalytically relevant palladium(0) (NHC)Pd(pyridine) precursors 1a,6a reveal significant donation from the N-heterocyclic carbene lone pair onto the unfilled ,* orbital of the trans Pd,pyridine bond. This weakens the Pd-bound "throwaway" pyridine ligand, and its dissociation marks the initiation of the catalytic cycle.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Controlled Synthesis of Cobalt Flowerlike Architectures by a Facile Hydrothermal RouteEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 17 2008Ya-jing Zhang Abstract Cobalt flowerlike architectures composed of hexagonal nanoplatelets have been synthesized by a simple hydrothermal reduction method. The architectures are fabricated by the reaction of CoCl2 with NaOH at 140,180 °C in the presence of sodium dodecyl benzenesulfonate (SDBS), with NaH2PO2·H2O as reducing agent. The diameters of the flowers range from 8 to 10 ,m, and the average thickness of the hexagonal sheets is about 100 nm. Higher reaction temperatures and the proper concentration of sodium hydroxide (NaOH) are key requirements for the fabrication of the flowerlike architectures. A growth mechanism for these architectures is proposed on the basis of the characterization by X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The magnetic hysteresis loops at 5 K and 295 K of the cobalt flowerlike architectures show ferromagnetic characteristics with coercivities of 371 Oe and 197 Oe, respectively. Our work may shed light on the designed fabrication of complex 3D architectures of other materials.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Microwave-Assisted Hydrothermal Synthesis of Structurally and Morphologically Controlled Sodium Niobates by Using Niobic Acid as a PrecursorEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2008Amauri J. Paula Abstract There are many advantages to using a microwave as a source of heat in hydrothermal reactions. Because it is a quick and homogeneous way to crystallize ceramic powders, it was used in this work for the production of antiferroelectric sodium niobate (NaNbO3) in a cubic-like form and its intermediary phase, disodium diniobate hydrate (Na2Nb2O6.H2O), with a fiber morphology. The syntheses were carried out by treating niobic acid (Nb2O5·nH2O) with NaOH. By changing the reaction time and the concentration of the reactants, particles with different structures and different morphologies could be obtained. The structural evolution of the products of this reaction was elucidated on the basis of the arrangement of the NbO6 octahedral units. Conclusive results were obtained with morphological and structural characterizations through XRD, TEM, MEV, and NMR and Raman spectroscopy. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Tetrahedral CoII Complexes with CoI2O2 and CoO2S2 Cores , Crystal Structures of [Co{HN(OPPh2)(SPPh2)- O}2I2] and [Co{N(OPPh2)(SPPh2)- O,S}2]EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 29 2007M. Carla Aragoni Abstract The compound [CoII{HN(OPPh2)(SPPh2)- O}2I2] (1) was synthesised by the reaction of cobalt in powder with the iodine adduct of tetraphenylthiooxoimidodiphosphinic acid, HN(OPPh2)(SPPh2), in Et2O; treatment of compound 1 with NaOH resulted in deprotonation of the ligands bound to the metal ion and a separation of [CoII{N(OPPh2)(SPPh2)- O,S}2] (2). Molecular structures of complexes 1 and 2 were elucidated by X-ray diffraction analysis, which revealed a CoI2O2 tetrahedral core for compound 1 in which two neutral ligands bind through the oxygen atoms the CoII ion, and a tetrahedral CoO2S2 core for compound 2 with the oxygen and sulfur atoms of each anionic ligand chelating a CoII centre. Variable-temperature magnetic susceptibility measurements are consistent with tetrahedral high-spin (S = 3/2) CoII that possesses a 4A2 ground state with best fit parameters g = 2.25, |D| = 12.0 cm,1 and g = 2.37, |D| = 11.9 cm,1 for complexes 1 and 2, respectively. The compounds were further characterised by UV/Vis and IR spectroscopy. DFT calculations were performed on model complexes [CoII{N(OPH2)(SPH2)- O,S}2] (3) and [CoII{N(SPH2)2 - S,S,}2] (4) to compare the electronic properties of the CoO2S2 and CoS4 cores. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Synthesis, Crystal Structure, and Magnetic Properties of Mn2(OH)2SO4: A Novel Layered HydroxideEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2004Mohsen Ben Salah Abstract Mn2(OH)2SO4, obtained as pink prismatic crystals by the hydrothermal reaction of MnSO4·H2O and NaOH at 240 °C for 24 h, consists of layers of Mn hydroxide connected to each other through µ6 -sulfate ions. Each layer exhibits vacancies, and each vacant space is capped at the top and bottom by the sulfate groups. The compound is paramagnetic above 50 K (C = 4.36 emu K mol,1, µeff = 5.91 µB, , = ,100 K). Below 45 K, the magnetization increases slightly, indicating canted-antiferromagnetic (TNéel = 42±1 K) behavior consistent with the linear dependence of the magnetization as a function of the field at 2 K, which reaches only 0.4 µB at 50 kOe, and the lack of any imaginary component of the ac-susceptibilities (ac = alternating current). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Alkaline neutralization of crude soybean oil by various adsorbentsEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 3 2008Sukran Kuleasan Abstract The effect of sodium hydroxide in neutralization was increased by using various adsorbents. NaOH in various concentrations was attached to the particles of Kieselguhr, Celite and Bentonite. The neutralization reaction was performed at ambient temperature, and different reaction times were applied. The soap formed after reaction was removed by centrifugation; thus, washing and drying steps were omitted. The amount of remaining soap, the acidity and color of oils were determined after each treatment. According to the results, free fatty acid neutralization in crude oil was achieved by Kieselguhr application. In this process, 9.5% NaOH was applied for 60,min of reaction time. The free fatty acid content of crude oil was decreased from 0.56 to 0.14%, and the remaining soap was found at 34,mg/kg after centrifugation. The use of adsorbents increased the efficiency of NaOH in the neutralization reaction and in the removal of soap from the neutralized oil. Neutralization with support material is a new and promising approach. The application is energy saving, more practical and in accordance with the strict environmental legislation about waste disposal. [source] Apatite Deposition on NaOH-Treated PEEK and UHMWPE Films for Sclera Materials in Artificial Cornea Implants,ADVANCED ENGINEERING MATERIALS, Issue 7 2010Monica Pino Abstract Cornea implants consist of a clear optic portion with a surrounding ring known as the skirt, which needs to integrate with the sclera. However, currently used skirt materials lead to poor tissue integration. Improvements in this respect may be achieved by using a bioactive skirt material that adapts to the metabolic activity of the cornea. Polyether etherketone (PEEK) and ultra-high molecular weight polyethylene (UHMWPE) might provide interesting alternatives, if they can be rendered bioactive. We, therefore, investigated the potential of surface-modifying PEEK and UHMWPE films through the use of a two-step treatment. This process involved a suitable chemical surface modification (via immersion in NaOH), with subsequent formation of apatite layers on the polymers' surfaces through exposure to supersaturated simulated body fluid (1.5 SBF). In the present work the effect of 5 and 10,M NaOH on formation of the apatite layer has been investigated with regard to wettability and topography features. In addition, the chemical stability of the apatite layer formed has been analyzed. Our data demonstrate that with an increase in NaOH concentration the wettability of the polymer increased, whilst some changes to the polymer film topography (increase/decrease in roughness) were observed. Most beneficially, the apatite layer that subsequently was grown on pre-treated PEEK and UHMWPE films through immersion in 1.5 SBF contained phosphate and carbonate ions, in similar ratios to those found in the apatite in dentine, thus, promising good in vivo bioactivity of these polymer films,a necessity if they are to be integrated into artificial cornea. [source] Medium Effect on the Reaction of N -Butyl-2,4,6-trinitroaniline with NaOH,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 13 2007María Laura Salum Abstract The kinetics of the reaction of N -butyl-2,4,6-trinitroaniline (3) with NaOH have been studied in 10 and 60,% 1,4-dioxane/H2O at 25 °C. In both cases, several processes were observed. In 10,% 1,4-dioxane/H2O the only product formed was 2,4,6-trinitrophenol (4), whereas in 60,% 1,4-dioxane/H2O a mixture of 4 and 5,7-dinitro-2-propyl-1H -benzimidazole 3-oxide (5) was observed in ratios that depend on the HO, concentration. A mechanism involving the formation of , complexes through the addition of one or two HO, anions to unsubstituted ring positions is proposed for 2,4,6-trinitrophenol formation. The presence of these complexes was confirmed by NMR studies in 60,% [D8]1,4-dioxane/D2O. The mechanism suggested for the formation of the N -oxide includes the cyclization of an N -alkylidene-2-nitrosoaniline-type intermediate as the rate-determining step. The decrease in solvent polarity produces a decrease in the observed rate constant for the formation of 4 of about one order of magnitude making the cyclization reaction a competitive pathway. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Asymmetric Synthesis of ,-Fluorinated ,-Amino Acid DerivativesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 4 2005Deepak M. Shendage Abstract Asymmetric alkylation of (S)-Boc-BMI (1a, BMI = 2- tert -butyl-3-methylimidazolidin-4-one) and its ,-methyl derivative 1b with 2-fluoroallyl tosylate, subsequent mild acidic deprotection of the products 2a and 2b, and basic hydrolysis of the thus formed N -methylamides 4a and 4b gave (S)-2-amino-4-fluoropent-4-enoic acid (5a) and (S)-2-amino-4-fluoro-2-methylpent-4-enoic acid (5b). Basic hydrolysis of compound 4a was accompanied by partial racemization, which was overcome by applying a new stereoconservative deamidation procedure. The alkylated cis -configured product 2a formed under kinetic control epimerized on refluxing with 2 n NaOH to give the thermodynamically more stable trans isomer 9. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Deprotonation of Indole Derivatives in Aqueous Cationic SurfactantsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 5 2004Nicoletta Spreti Abstract Deprotonations of 5-nitroindole, 1a, and its 2-carboxylate ion, 2a, have been monitored in 0.01, 0.1, and 0.5 M NaOH in micellar solutions of cetyl trialkylammonium bromide, alkyl = Me, Et, nPr, nBu, CTABr, CTEABr, CTPABr, CTBABr. Extents of deprotonation (% f) have been fitted using the pseudophase model of micellar effects with interionic competition described by ion exchange or by independent association constants. Both treatments indicate that base dissociation constants in dilute OH, are lower than in water by factors of ca. 3,11, and decrease with increasing bulk of the head groups, and that these factors increase modestly as the OH, concentration increases to 0.5 M. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Antioxidants in soil organic matter and in associated plant materialsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2009D. L. Rimmer Summary The presence of antioxidants in soil could have a significant effect on the dynamics of soil organic matter. In this paper we report some preliminary experiments, which demonstrate that antioxidants can be extracted from soils and that the quantities vary from soil to soil. Extraction with 1.0 m NaOH was effective, and this was then used on a range of mineral and organic soils, and the antioxidant capacity of the resulting extracts was measured. The antioxidant capacities obtained were positively correlated with soil carbon contents and with the dissolved organic carbon contents of the extracts. Expressing the data per mass of soil carbon showed that the antioxidants generally decreased with depth in the soil profile, suggesting that they were subject to degradation during humification. In a follow-up study, soil, litter and fresh plant samples were collected from 15 sites with a wide variety of vegetation types and analysed for their antioxidant capacities. The aim was to show that the antioxidant capacities in the soils were related to the antioxidant capacities of the fresh plant material and/or litter above. The antioxidant capacities of the soil samples were less than those in either fresh material or litter. While there was a significant positive relationship between the antioxidant capacities of fresh material and litter, no relationship existed between the antioxidant capacities of the soils and those of either fresh material or litter. [source] Ammonium fluoride extraction for determining inorganic sulphur in acid forest soilsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2000J. Prietzel Summary Current methods for determining inorganic sulphur (S) in aerated mineral soil horizons often result in underestimates. To overcome this defect we developed a new method combining a batch extraction with 0.5 m NH4F solution at a soil:solution ratio of 1:5 with a subsequent analysis of the mobilized SO42, by ion chromatography. The ammonium fluoride extraction enables us to characterize inorganic sulphate in non-calcareous forest soils. It is more efficient than conventional procedures in which inorganic S is extracted with phosphate or bicarbonate solution. In contrast to the extraction with strongly alkaline reagents (NaOH, KOH, LiOH), the NH4+,NH3 buffer system in NH4F prevents the pH of the suspension from exceeding 9.0 and thus the undesired conversion of organic S into SO42, by auto-oxidation and hydrolysis of ester sulphate. In a comparison we demonstrated that the inorganic S in six German forest soils is underestimated by up to 50% or 200 kg S ha,1 in the uppermost 60 cm, if it is assessed by extraction with 0.016 m KH2PO4 or 0.5 m NaHCO3 instead of 0.5 m NH4F. Conversely, the pool of ester sulphate is overestimated almost threefold. [source] Electrochemical Reduction of Oxygen on Carbon Supported Pt and Pt/Ru Fuel Cell Electrodes in Alkaline SolutionsFUEL CELLS, Issue 4 2003E.H. Yu Abstract A study of O2 reduction in 1 M NaOH solution at gas diffusion electrodes made from carbon supported Pt and Pt/Ru catalysts is reported. Two Tafel regions were observed for both the Pt and Pt/Ru electrodes. Although the same mechanism was suggested for oxygen reduction on both Pt and Pt/Ru catalysts, the O2 reduction activity was lower on Ru. Electrochemical Impedance Spectroscopy (EIS) analysis was carried out at different potentials and showed the significant contribution of diffusion on the reaction process and kinetics. The effect of methanol on O2 reduction was investigated in solutions containing various concentrations of methanol. The electrode performance deteriorated with increasing methanol concentration because of a mixed cathode potential. The methanol tolerance, i. e., the methanol concentration which polarises the O2 reduction reaction for O2 reduction, at the Pt/C electrode with a Pt loading of 1.2 mg cm,2 is 0.2 M methanol in 1 M NaOH. [source] Cover Picture: Tailored Mesoporosity Development in Zeolite Crystals by Partial Detemplation and Desilication (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 1 2009Mater. On page 164, Pérez-Ramírez et al. demonstrate that partial detemplation followed by desilication in alkaline media is a powerful and elegant approach for the design of hierarchical zeolites with a tailored degree of mesoporosity. This achievement, illustrated for large beta crystals, is based on the distinct capability of NaOH to extract silicon in template-containing or template-free regions of the zeolite. The introduced mesoporosity enhances the effectiveness of the materials in catalysis due to shorter diffusion lengths. [source] An Efficient Synthesis of 3,-Amino-3,-deoxyguanosine from GuanosineHELVETICA CHIMICA ACTA, Issue 3 2003Lei Zhang 3,-Amino-3,-deoxyguanosine was synthesized from guanosine in eight steps and 58% overall yield. The 2,,3,-diol of 5,- O -[(tert -butyl)diphenylsilyl]-2- N -[(dimethylamino)methylidene]guanosine was reacted with , -acetoxyisobutyryl bromide and treated with 0.5n NH3 in MeOH to yield 9-{2,- O -acetyl-3,-bromo-5,- O -[(tert -butyl)diphenylsilyl]-3,-deoxy- , - D -xylofuranosyl]-2- N -[(dimethylamino)methylidene]guanine, which was reacted with benzyl isocyanate, NaH, and then 3.0n NaOH, and finally with Pd/C (10%) and HCO2NH4 in EtOH/AcOH to afford 3,-amino-3,-deoxyguanosine. [source] Phosphono-substituted isoindolines and indoles from 2,3- and 2,4-benzoxazin-1-onesHETEROATOM CHEMISTRY, Issue 1 2004Wafaa M. Abdou Reactions of 2,3-benzoxazinone 1 and 2,4-benzoxazinone 2, with trialkyl phosphites 3a,c provide access to new phosphono-substituted isoindolines 6a,f and indoles 19a,e, respectively. Phosphono-substituted 2,3-benzoxazines 5a,c were also obtained in the first reaction. Bisisoindolinylidene (7) was, however, isolated in low yields when 1 was heated with triethyl or triisopropyl phosphite at 100deg;C whereas at 170deg;C 7 was obtained as the major product (,53%). On the other hand, the reaction of 1 or 2 with dialkyl phosphonates 4a,c proceeded in the presence of aqueous solution of NaOH (5%) to give the respective alkylated product 14a,c or 20a,c. © 2003 Wiley Periodicals, Inc. 15:77,84, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/.10216 [source] Kinetics and mechanism of alkaline hydrolysis of 4-nitrophthalimide in the absence and presence of cationic micellesINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 7 2001M. Niyaz Khan Pseudo-first-order rate constants (kobs) for alkaline hydrolysis of 4-nitrophthalimide (NPTH) decreased by nearly 8- and 6-fold with the increase in the total concentration of cetyltrimethyl-ammonium bromide ([CTABr]T) from 0 to 0.02 M at 0.01 and 0.05 M NaOH, respectively. These observations are explained in terms of the pseudophase model and pseudophase ion-exchange model of micelle. The increase in the contents of CH3CN from 1 to 70% v/v and CH3OH from 0 to 80% v/v in mixed aqueous solvents decreases kobs by nearly 12- and 11-fold, respectively. The values of kobs increase by nearly 27% with the increase in the ionic strength from 0.03 to 3.0 M. The mechanism of alkaline hydrolysis of NPTH involves the reactions between HO, and nonionized NPTH as well as between HO, and ionized NPTH. The micellar inhibition of the rate of alkaline hydrolysis of NPTH is attributed to medium polarity effect. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 407,414, 2001 [source] An empirical approach to study the occurrence of ion exchange in the ionic micellar-mediated semi-ionic reactions: Kinetics of the rate of reaction of piperidine with ionized phenyl salicylate in the presence of cationic micellesINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 5 2001M. Niyaz Khan Pseudo-first-order rate constants (kobs),obtained for the cleavage of ionized phenyl salicylate (PS,) at constant [NaOH], [MeCN], [CTAZ]T (total concentration of cetyltrimethylammonium chloride and bromide), [Pip]T (total concentration of piperidine), and varying concentrations of sodium cinnamate, acetate, and butanoate ([NaX]),follow the relationship: kobs = (k0 + , K[NaX])/(1 + K[NaX]), where , and K are empirical parameters. The values of , are almost independent of [CTAZ]T, while K values decrease with the increase in [CTAZ]T within its range 0.006,0.020 M. The values of , and K are explained in terms of pseudophase model of micelle coupled with an empirical relationship: KS = KS0/(1 + ,X/S [NaX]), where KS is the CTAZ micellar binding constant of PS, in the presence of NaX. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 288,294, 2001 [source] | ||||||||||||||||||||||||||||||||||||||||||||||