Voltammetric Study and Detection of Methane on Nickel Hydroxide–Modified Nickel Electrode

Abstract

The nickel hydroxide–modified nickel (NMN) electrode was prepared by cyclic voltammetry. The modified electrode exhibited better catalytic effect toward electrochemical oxidation of methane in 1.0 mol · L^?1 NaOH solution. The catalytic activation of nickel hydroxide on the nickel electrode surface was investigated in different supporting electrolyte solutions by the cyclic voltammetry method in detail, and the related electrochemical oxidation of methane at the NMN electrode was first proposed by amperometric i‐t curve method under the experiment conditions. The results indicated that in the 1.0 mol · L^?1 NaOH solution, the anodic peak current increased with the increased concentration of methane.     

Extraction—Spectrophotometric determination of nickel with 2-hydroxy-1-naphthaldoxime

A method for the solvent extraction—spectrophotometric determination of nickel with 2-hydroxyl-1-naphthaldoxime (HNA) has been studied. The method is based upon the formation of a nickel—HNA complex which is extracted into chloroform from an aqueous solution of pH 5.8. The nickel—HNA complex in chloroform exhibits an absorption maximum at 410 nm with molar absorptivity of 8.1 × 10³ liters mol^?1 cm^?1. Beer's law is applicable in the range from 5 to 50 μg of nickel. The mole ratio of the complex and effect of interfering ions are described.     

Chiral Separation of 4-Iminoflavan Derivatives on Several Polysaccharide-Based Chiral Stationary Phases by HPLC

The HPLC enantiomeric separation of seven 4-iminoflavans was successfully accomplished in the normal phase mode using six polysaccharide-based chiral stationary phases namely, Chiralcel^®OD-H, Chiralcel^®OD, Chiralcel^®OJ, Chiralpak^®AD, Chiralpak^®IA and Chiralpak^®IB under normal and polar organic phase modes. The resolution depended on nature and concentration of alcoholic modifier. The results demonstrate clearly that the chromatographic system based on the coated and immobilized type Chiralpak^®IB and Chiralcel^®OD-H CSPs provide a powerful analytical tool for enantiomeric separation of all the 4-iminoflavans used in this study.

     

A Comparison Between a Micro and an Ultramicro Circle® Cell for on-Line Ft-Ir Detection in a Reverse Phase HPLC System

Abstract

Caffeine and theophylline peaks separated on a 300 × 7.8 mm C₁₈ column could be distinguished qualitatively by FT-IR detection using two types of cylindrical internal reflectance (CIRCLE^®) cells. Detection limits and limits of identification, on the order of 0.2%, are lower for the micro CIRCLE^® cell as compared to the ultramicro CIRCLE^® cell. Maximum sample capacity of the column used was 50uL of a 0.4% solution of caffeine (1.0 micromoles).     

Surface Behavior of Aminosulfonate Formaldehyde Condensates and Its Dispersion Effect on Cement Paste

The surface physicochemical properties of aminosulfonate formaldehyde condensates (ASP) and naphthalene sulfonate formaldehyde condensates (FDN) and the dispersion effect on cement paste were investigated. The results showed that these two superplastcizers could hardly reduce the surface tension of aqueous solution, and the surface activity and foam production was rather weak. The adsorption of ASP and FDN on the cement particles followed the Langmuir adsorption equation, characterized as monolayer adsorption. The maximum adsorptive amount of ASP on the cement particles was 3.83 mg/g at 20°C, and the adsorption rate constant was 1.00 s^?1, which were less than those of FDN, respectively. The ζ potential of cement particles containing ASP was larger than that containing FDN, and the loss of ζ potential was much less. Study on the XPS spectrograms presented that, the thickness of adsorption layer of ASP on the cement particles was 7.26 nm, while that of FDN was 1.50 nm. It could be concluded that the electrostatic repulsion effect and steric repulsion effect of ASP were stronger than those of FDN, hence ASP had better dispersion effect and fluidity‐retaining ability on the cement paste. When the dosage of superplasticizer was 0.5 wt% of the cement, the fluidity of cement paste with adding ASP was 270 mm, while that with adding FDN was only 150 mm at a mass ratio of water to cement of 0.28. The residual fluidity of cement paste with adding ASP was 167 mm with 2.5 h elapsed at an initial fluidity of 200 mm, while that with adding FDN was only 101 mm.     

A thermodynamic study of nickel ion interaction with bovine carbonic anhydrase II molecule

A thermodynamic study on the interaction of bovine carbonic anhydrase II (CAII) with nickel ions was performed by using isothermal titration calorimetry (ITC) at 27 °C in Tris buffer solution at pH = 7.5. The enthalpies of Ni²⁺ + CAII interaction are reported and analysed in terms of the new solvation theory. It was indicated that there are three identical and non-cooperative sites for Ni²⁺. The binding of a nickle ion is exothermic with dissociation equilibrium constants of 81.306 and 99.126 μM at 27°C and 37°C, respectively. The binding of nickel ions can cause some changes in the stability of the enzyme at low and high Ni²⁺ concentrations.     

Preparation and characterization of an electronically conductive and chemically modified ultrafiltration type membrane

We have prepared, for the first time, an electronically conductive polyethersulfone ultrafiltration membrane, noted as PS, by depositing an ultrathin gold coating. This conductive membrane has been chemically modified by electrodepositing a polymer-based nickel tetrasulfonated phthalocyanine film (NiTSPc) covered by Nafion^®. Atomic force microscopy (AFM) and membrane potential measurement experiments were carried out to characterize the morphology and the transport properties of the new PS membrane. AFM measurements showed that the topology of the surface pores of the PS membrane was modified by the deposition of Au, NiTSPc and Nafion^® layers and that the chemical modifications of the membrane do not obstruct the access to the inner pores. Li⁺ transport number determination have corroborated AFM results and showed that the Li⁺ transport was facilitated by electrostatic effect induced by the negative charge densities of NiTSPc and NiTSPc/Nafion^® coatings.     

Sorption of nickel on chitosan

The sorption of nickel on chitosan was studied using batch method. As a tracer was used radioisotope ⁶³Ni. The effect of pH and contact time to reach sorption equilibrium was investigated. During the sorption of Ni²⁺ ions occur mostly to ion-exchange reactions on the surface of sorbent. The time to reach the sorption equilibrium of nickel on chitosan was 14 h. The percentage of sorption after 14 h achieved the value of 84 %. On the sorption of nickel used solutions with initial pH in the range from 3.9 to 8.1. In the monitored range of pH after 24 h of contact was the sorption of nickel on chitosan >97 %. The sorption of nickel was reduced by increasing concentrations of Ni²⁺ ions in the solution. The experimental data for sorption of nickel have been interpreted in the term of Langmuir isotherm and the value of maximum sorption capacity of nickel on chitosan was 2.71 × 10^?3 mol g^?1.     

Complexation of Nickel Ions by Boric Acid or (Poly)borates

An experiment based on electrochemical reactions and pH monitoring was performed in which nickel ions were gradually formed by oxidation of a nickel metal electrode in a solution of boric acid. Based on the experimental results and aqueous speciation modeling, the evolution of pH showed the existence of significant nickel–boron complexation. A triborate nickel complex was postulated at high boric acid concentrations when polyborates are present, and the equilibrium constants were determined at 25, 50 and 70 °C. The calculated enthalpy and entropy at 25 °C for the formation of the complex from boric acid and Ni²⁺ ions are respectively equal to (65.6 ± 3.1) kJ·mol^?1 and (0.5 ± 11.1) J·K^?1·mol^?1. The results of this study suggest that complexation of nickel ions by borates can significantly enhance the solubility of nickel metal and nickel oxide depending on the concentration of boric acid and pH. First principles calculations were investigated and tend to show that the complex is thermodynamically stable and the nickel cation in solution should interact more strongly with the \( {\text{B}}_{3} {\text{O}}_{3} \left( {\text{OH}} \right)_{4}^{ - } \) than with boric acid.     

Conditional Stability Constant Determination of Metal-Fulvic Acid Complexes

Abstract

Conditional stability constants for metal complexes of a terrestrial fulvic acid were determined using an ion-exchange chromatography—atomic absorbance spectroscopy method. Employing the Scatchard model, conditional stability constants were determined for the metal (II) fulvic acid complexes of cadminum, copper, lead, nickel, manganese, and zinc. The order of metal binding by the fulvic acid was determined to be: Cu > Ni > Pb > Zn > Cd > Mn. Complexes of weakly bound metal ions were determined with an added metal ion concentration of 2 × 10^–5 M to 1 × 10^–4 M while complexes of strongly bound metal ions were determined with an added metal ion concentration of 1 × 10^–5 M to 8 × 10^–4 M. The fulvic acid concentration was kept constant at 4 × 10^–4 M. The effect of pH and ionic strength on the copper-fulvic acid complex also was investigated.     

Wetting properties of aqueous solutions of hydrophobically modified inulin polymeric surfactant

The contact angles of aqueous solutions of a polymeric surfactant namely hydrophobically modified inulin (INUTEC®SP1) were measured on hydrophilic and hydrophobised quartz glass surfaces using the sessile drop technique. These measurements showed a large difference (>10°) between the advancing contact angle θ ₁ (that is measured immediately after placing the drop on the surface) and the constant contact angle θ ₂ (that is measured 30 minutes after placing the drop). In all the results only the contact angle θ ₂ was subsequently measured. θ versus INUTEC®SP1 concentration C _s curves were obtained at various NaCl concentrations both on hydrophilic and hydrophobic glass surfaces. On hydrophilic glass surface the θ versus C _s curves showed a maximum at a concentration range of 10^–6 to 2?×?10^–5 mol dm^-3 INUTEC®SP1. These curves were shifted to lower values as the NaCl concentration was increased. On such hydrophilic surface the INUTEC®SP1 molecule adsorbs with the polyfructose loops and tails oriented towards the surface leaving the alkyl chains in solution. Saturation adsorption with this orientation occurs at 2?×?10^–5 mol dm^-3 INUTEC®SP1. However, the contact angles remain quite small (<18°) indicating the presence of several hydrophilic glass patches uncovered by surfactant molecules. At C _s?>?2?×?10^–5 mol dm^-3 θ decreases with further increase of the INUTEC®SP1 concentration reaching 5° at the Critical Association Concentration (CAC) of the polymer. This indicates the formation of a bilayer of INUTEC®SP1 molecules with the alkyl chains hydrophobically attached to those of the first layer. On a hydrophobic glass surface, adsorption of INUTEC®SP1 occurs by multi-point attachment with the alkyl chains on the surface leaving the hydrophilic polyfructose loops and tails dangling in solution. This results in a gradual decrease of the contact angle with increase in INUTEC®SP1 concentration, reaching a plateau value (>85°) between 2?×?10^–5 and 2?×?10^–4 mol dm^-3. The large contact angles obtained on adsorption of the polymeric surfactant on a hydrophobic surface indicate the presence of several uncovered hydrophobic patches. These results give a reasonable picture of the adsorption and orientation of the INUTEC®SP1 molecules on both hydrophilic and hydrophobic solid surfaces.     

Combined use of cyclodextrins and hydroxypropylmethylcellulose stearoxy ether (Sangelose®) for the preparation of orally disintegrating tablets of type-2 antidiabetes agent glimepiride

Despite recent advances in the formulation of orally disintegrating tablets (ODTs), the efforts to enhance the swallowing of the drug after disintegration have been limited. In this study, the feasibility of the combined use of cyclodextrins (CyDs) and a functional drug carrier, hydroxypropylmethylcellulose stearoxy ether (Sangelose^®) was investigated to improve usability of ODTs. Glimepiride, a potent third generation hypoglycemic agent for type 2 diabetes was used as a model drug, because it is poorly water-soluble and elimination half life is fairly short. The direct compression method was employed for the preparation of glimepiride tablets, containing CyDs and Sangelose^®, and various characteristics of the tablets were examined. In the cases of α-CyD and β-CyD, a short disintegration time with an appropriate hardness was obtained, complying with ODT criteria. On the other hand, γ-CyD, HP-β-CyD and HB-β-CyD increased in the hardness and disintegration time of the tablets. The rheological evaluation revealed that CyDs, except γ-CyD, significantly reduced the viscosity of the fluids after disintegration of the tablets, suggesting an ease of swallowing. This was ascribable to the complexation of the hydrophobic stearoyl moiety of Sangelose^® with CyDs after dissolution, leading to the inhibition of the polymer–polymer interaction of Sangelose^® and to the decrease in viscosity of the solution. The interaction of glimepiride with α- and β-CyDs was studied by the solubility method, demonstrating that glimepiride formed water-soluble complexes with these CyDs. Results obtained here suggested that α-CyD and β-CyD can be particularly useful for the Sangelose^®-based ODT formulation, compared to γ-CyD, HP-β-CyD and HB-β-CyD, because of the short disintegration time of the tablets containing α-CyD and β-CyD, their shear-thinning effect on Sangelose^® solutions and their solubility enhancing effect on the drug.     

Synthesis of some 5,10,15,20-tetraalkylchlorin and tetraalkylporphyrin complexes of transition metals

Metal-assisted template syntheses of 5,10,15,20-tetraalkylchlorin and tetraalkylporphyrin complexes of transition metals are described. With Co only the porphyrins are obtained; with Cu only the chlorins; with Ni a mixture of chlorin and porphyrin is obtained depending on alkyl and added anhydride. As opposed to the higher alkyls, (5,10,15,20-tetramethylporphyrinato)nickel(II) dimerizes in solution, a dimerization constant of 3.9 ± 1.3 M^?1 being derived from ¹H nmr data.     

Optimizing the sensitivity and radiological properties of the PRESAGE® dosimeter using metal compounds

The aim of this study is to investigate the radiation-modifying effects of incorporating commercially available bismuth-, tin- and zinc-based compounds in the composition of the PRESAGE^® dosimeter, and the feasibility of employing such compounds for radiation dose enhancement. Furthermore, we demonstrate that metal compounds can be included in the formulation to yield water-equivalent PRESAGE^® dosimeters with enhanced dose response. Various concentrations of the metal compounds were added to a newly developed PRESAGE^® formulation and the resulting dosimeters were irradiated with 100 kV and 6 MV photon beams. A comparison between sensitivity and radiological properties of the PRESAGE^® dosimeters with and without the addition of metal compounds was carried out. Optical density changes of the dosimeters before and after irradiation were measured using a spectrophotometer. In general, when metal compounds were incorporated in the composition of the PRESAGE^® dosimeter, the sensitivity of the dosimeters to radiation dose increased depending on the type and concentration of the metal compound, with the bismuth compound showing the highest dose enhancement factor. In addition, these metal compounds were also shown to improve the retention of the post-response absorption value of the PRESAGE^® dosimeter over a period of 2 weeks. Thus, incorporating 1–3 mM (ca. 0.2 wt%) of any of the three investigated metal compounds in the composition of the PRESAGE^® dosimeter is found to be an efficient way to enhance the sensitivity of the dosimeter to radiation dose and stabilize its post-response for longer times. Furthermore, the addition of small amounts of the metal compounds also accelerates the polymerization of the PRESAGE^® dosimeter precursors, significantly reducing the fabrication time. Finally, a novel water-equivalent PRESAGE^® dosimeter formula optimized with metal compounds is proposed for clinical use in both kilovoltage and megavoltage radiotherapy dosimetry.     

Electrochemical Impedance Spectroscopy of 3 MeV Nickel Implanted into Steel

ABSTRACT

Impedance spectroscopy was used to study the corrosion of a nickel implanted steel sample. The dosaye was 5 × 10¹⁵ ions/cm² and the energy of the nickel ions was 3 MeV. The data from a Simple Randies circuit (R_p and C_dl) were used to explain the corrosion changes observed in a NACE National Association of Corrosion Engineers) Brine solution (used to emulate geothermal brine conditions) at pH 2.0 and 25°C in an air saturated solution. Iron concentrations measured by Induction Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) were used to calculate corrosion rates at various time intervals. Impedance spectroscopy^1,2 is an electrochemical technique which can be used to monitor corrosion and to our knowledge it has not been applied to implanted materials.     

Influence of Intra-articular Neutrophils on the Effects of Photodynamic Therapy for Murine MRSA Arthritis

Although there have been some reports about the cytotoxic effects of photodynamic therapy (PDT) on multidrug-resistant bacteria, there have been few reports in which favorable results of PDT on a local infection site are described. This study aimed to verify the hypothesis that the low efficacy of PDT on a local infection site is due to the cytotoxic effect of PDT on leukocytes. PDT using Photofrin^® exerted significant cytotoxicity for cultured methicillin-resistant Staphylococcus aureus (MRSA). Nevertheless, this therapeutic modality was not effective for a murine MRSA arthritis model. Approximately 30% of intra-articular leukocytes, mainly neutrophils, died immediately after PDT, and a further decrease in the number of intra-articular leukocytes and atrophy of the synovial tissue were seen 24 h after PDT. Isolated peripheral neutrophils showed significant affinity for Photofrin^® and showed significant morphological damage, resulting in cell death, when they were subject to PDT using Photofrin^®. These results indicate that intra-articular neutrophils have an influence on the effects of PDT for MRSA arthritis.     

Hydration of Portland cement in the presence of high activity aluminum hydroxides

The effect of highly dispersed amorphous aluminum hydroxides on the hydration of Portland cement was studied by the solid-state ²⁷Al and ²⁹Si NMR spectroscopy. It was established that in the presence of aluminum hydroxides the decrease in the setting time of a cement paste is due to rapid formation of ettringite phase, with contribution of admixture material the main and contribution of aluminum-containing phases at this stage insignificant.     

A LabVIEW®-based software for the control of the AUTORAD platform: a fully automated multisequential flow injection analysis Lab-on-Valve (MSFIA-LOV) system for radiochemical analysis

A LabVIEW^®-based software for the control of the fully automated multi-sequential flow injection analysis Lab-on-Valve (MSFIA-LOV) platform AutoRAD performing radiochemical analysis is described. The analytical platform interfaces an Arduino^®-based device triggering multiple detectors providing a flexible and fit for purpose choice of detection systems. The different analytical devices are interfaced to the PC running LabVIEW^®VI software using USB and RS232 interfaces, both for sending commands and receiving confirmation or error responses. The AUTORAD platform has been successfully applied for the chemical separation and determination of Sr, an important fission product pertinent to nuclear waste.

     

Amperometrische Bestimmung von Pflanzenschutzmitteln in technischen Wirkstoffen und Formulierungen

A process was developed which made possible the determination of smallest quantities of nickel(II) using the above method and an electrolyte consisting of 0.1 M KNO₃ and 0.02 M KSCN. In the concentration range of 5×l0^?6 to 5×10^?8 M nickel(II) an excellent linear relationship between the anodic dissolution currents of nickel enriched on the mercury drop and the nickel(II) concentration in the solution was established, under the condition, however, that the nickel concentration in the mercury is not too high; otherwise the method is no longer reproducible.     

Factors Affecting Selenium Atomization Efficiency in Graphite Furnace Atomic Absorption

Abstract

The effect of graphite furnace surface treatment, and the addition of “matrix modifiers” such as nickel or lanthanum on the observed selenium atomization siqnal in electrotherval atomic absorption analysis has been investiqated. The results indicate that the removal of signal depression caused by the addition of metal solution to analyte solution is not simply a devolatilization of the selenium. The effect appears to be a modification of the graphite surface which leads to more efficient atom formation. The role of the surface was investigated monitoring the atomic absorption signal generated from graphite furnaces which were untreated, pyrolytic graphite-coated, zirconium-or tantalum-coated, and metal-coated followed by pyrolytic graphite coating. The dependence of the analyte signal on the concentration of added metal was investigated for these surfaces. The optimum results obtained were the metal-coated/pyrolytic graphite-coated cuvettes. These cuvettes showed reduced effect of “matrix modifier,” suggesting that the surface treatment can replace the “matrix modifer,” Surface chemistry consistent with the atomic absorption observations and surface analysis data is presented.