Carbon Dioxide Reforming of Methane Using a Dielectric Barrier Discharge Reactor: Effect of Helium Dilution and Kinetic Model

The carbon dioxide reforming of methane to synthesis gas was investigated in a dielectric barrier discharge reactor at room temperature. The influence of dilution of reactants by helium was studied. We showed that, at a fixed contact time, the conversions of CH₄ and CO₂ increase when the amount of helium in the gas mixture increases. This result is attributed to the “penning ionization” phenomenon, which corresponds to an energy transfer from excited He to molecules in ground state (CH₄, CO₂). The selectivity to products is affected by the dilution factor. As soon as helium is present in a large amount the formation of products resulting from recombination of methyl radicals (such as C₂, C₃ and C₄) is less favourable due to the lowest probability of collisions to proceed. A kinetic model is proposed based on the assumption that the reactant molecules CH₄ or CO₂ are attacked by active species produced by the plasma discharges, and the production of this active species are function of the plasma power. This model which takes into account the dilution by helium fits particularly well the experimental data we obtained.     

Using Ferrocenes to Assist in Voltammetric Characterization of Carbon Fiber Microelectrodes after Electrochemical and Laser Activation

In this report the voltammetry of water‐soluble ferrocene derivatives is used to characterize the surface of carbon fiber microelectrodes before and after both electrochemical and laser activation procedures. Activation of carbon electrodes is necessary to produce a reproducible surface that will allow fast electron transfer. However, the activation method that is best suited for a given analysis can differ with analyte. In order to directly compare activation methods and characterize the resulting electrode performance, the voltammetry of a set of ferrocenes which have fast and well‐known electrochemistry has been used. As expected, electrochemical activation (0.000 to 2.000 V (vs. SSCE) at 500 V/s for 15 seconds) resulted in a hydrophilic surface with increased surface area. Laser pretreatment (20 Hz pulsed nitrogen laser irradiation for 15 seconds) appeared to remove surface oxides thereby producing a more hydrophobic surface that facilitates the adsorption of neutral analytes. In general, anionic ferrocene derivatives exhibited more quasi‐reversible voltammetry and were not as strongly adsorbed as the neutral analyte, particularly with electrochemically activated probes. In addition, neutral analytes show considerable adsorption, particularly at laser‐activated electrodes, while the cationic analyte shows significant adsorption at only the electrochemically‐pretreated electrodes, indicating surface‐specific interactions.     

A Model of Joint Absorption of Hydrogen Sulfide and Carbon Dioxide in a Moving Drop of Alkaline Solution

A mathematical model of hydrogen sulfide and carbon dioxide absorption by a moving drop of alkaline solution is proposed on the basis of a theoretical analysis of the process. The results obtained in solving numerically the equations of the model are presented and analyzed.     

Comparison of the In Vivo Photodynamic Threshold Dose for Photofrin, Mono- and Tetrasulfonated Aluminum Phthalocyanine Using a Rat Liver Model

The photodynamic threshold dose in normal rat liver was determined from the measured depth of necrosis following surface irradiation. The threshold was determined for the photosensitizing drugs Photofrin and monosulfo-nated aluminum chlorophthalocyanine, AIPcS₁, at 24 h postinjection and was found to be (3.4 ×/÷ 1.3) × 10¹⁸ (8.2 ×/÷ 1.5) × 10¹⁸photons cm^-3, respectively, compared with the previously reported value of (38 ± 2) × 10¹⁸photons cm^-3for the tri/tetrasulfonated phthalocyanine, AlPcS₄. These values were independent of drug concentration or total light fluence. For all three drugs the depth of tissue necrosis decreased as the time between drug and light administration increased from 10 min to 72 h. This decrease can be attributed both to the change in the tissue drug concentration as well as to changes in the efficiency of photodynamic therapy for producing tissue damage, related to the photodynamic necrosis threshold. 1'he threshold values for all three photosensitizers were lowest at 10 min post injection: (1.4 ×/÷ 1.4) × 10¹⁸, (1.6 ×/÷ 1.3) × 10¹⁸ (23 ×/÷ 1.3) × 10¹⁸photons cm^-3for Photofrin, AIPcS₁ and AlPcS₄, respectively. The changes in necrosis threshold with time may be due to an initial change from entirely vascular to a combination of vascular and cellular damage, with later redistribution of the photosensiti/.er to targets at the subcellular level.     

Potentials of Oxide Electrodes in Cells with a Zirconium Dioxide-Based Electrolyte in Mixtures of Nitrogen,Oxygen, Carbon Dioxide,and Carbon Monoxide Gases

Measurements of steady-state potentials of various electrodes made of oxide compositions are performed in cells containing electrolyte ZrO₂ + 10 mol % Y₂O₃ at a temperature of 773 K in nonequilibrium gas mixtures N₂ + O₂ + 20 vol % CO₂ + CO, with variable CO (0.1–5 vol %) and O₂ (0.5–10 vol %) contents. After adding CO into a gas phase, potentials of all electrodes shift, to one degree or another. The shift is substantially affected by the O₂ content. The electrochemical systems under study are of some interest for analyzing partial pressures of CO in gas mixtures. The discovered effect must be taken into account when employing such electrodes for the determination of partial concentrations of other components of a gas mixture, for example, oxygen.     

Formation of Polyhydroxyurethanes in the Reaction of Carbon Dioxide with Diepoxides and Diamines in the Presence of a Chromium Complex

Kinetics and Catalysis - Cyclic biscarbonates were synthesized from CO2 and diepoxides in the presence of a chromium(III) salen complex. The effect of the reaction conditions on the process...     

Reaction Kinetics of Carbon Dioxide (CO2) Absorption in Sodium Salts of Taurine and Proline Using a Stopped‐Flow Technique

The pseudo–first‐order reaction rate constants (k₀, s^?1) for the reaction of carbon dioxide in aqueous solutions of sodium taurate (NaTau) and sodium prolinate (NaPr) were measured using a stopped‐flow technique at a temperature range of 298–313 K. The solutions concentration varied from 5 to 50 mol m^?3 and from 4 to 12 mol m^?3 for NaTau and NaPr, respectively. Comparing the k₀ values, aqueous NaPr was found to react very fast with CO₂ as compared with the industrial standard aqueous monoethanolamine (MEA) and aqueous sodium taurate (NaTau) was found to react slower than aqueous MEA at the concentration range considered in this work. For the studied amino acid salts, the order of the reactions was found to be unity with respect to the amino acid salt concentration. Proposed reaction mechanisms such as termolecular and zwitterion reaction mechanisms for the reaction of CO₂ with aqueous solutions were used for calculating the second‐order reaction rate constants (k₂, m³ mol^?1 s^?1). The formation of zwitterion during the reaction with CO₂ was found to be the rate‐determining step, and the deprotonation of zwitterion was instantaneous compared to the reverse reaction of zwitterion to form an amino acid salt. The contribution of water was established to be significant for the deprotonation of zwitterion. Comparing the pseudo–first‐order reaction rate constants (k₀, s^?1) of various amino acid salts with CO₂, NaPr was found to be the faster reacting amino acid salt. The activation energy for NaTau was found to be 48.1 kJ mol^?1 and that of the NaPr was found to be 12 kJ mol^?1. The Arrhenius expressions for the reaction between CO₂ and the studied amino acid salts are      

低碳铺底二元助熔法测定钢铁中高碳

电弧燃烧碳硫自动分析仪，对一般的钢铁试样分析很合适，但对于高碳的生铁试样分析有很大困难。如按常规法，改变滴定液的浓度，碱性过强，一是严重腐蚀吸收杯，二是滴定误差太大；如果改变称样量，试样太少，又给引弧带来困难。针对这一问题，通过试验，选取了低碳铺底二元助熔法，解决     

In vitro and in vivo evaluation of a novel anti-EGFR antibody labeled with 89Zr and 177Lu

Journal of Radioanalytical and Nuclear Chemistry - There is an urgent need to develop more specific targeted therapies for lung cancer treatment due to the its low survival rate. EGFR is a...     

微渗析取样-羧基化多壁碳纳米管修饰电极色谱电化学用于活体检测的研究

研制了一种新型的羧基化多壁碳纳米管修饰电极作为液相色谱电化学检测器;并将该修饰电极与高效液相色谱联用有效地分离和检测了半胱氨酸(Cys)和谷胱甘肽(GSH)两种巯基化合物,其检出限分别为1.2×10-7mol／L和2.2×10-7mol／L;结合微渗析活体取样技术测定了大鼠脑内纹状体中Cys和GSH的浓度分别为(2.22±0.16)×10-6mol／L和(2.75±0.14)×10-6mol／L,标准加入回收率分别为96%和103%。     

Simultaneous Determination of Epinephrine and Dopamine by Using Candida tropicalis Yeast Cells Immobilized in a Carbon Paste Electrode Modified with Single Wall Carbon Nanotube

A new electrochemical microbial biosensor system based on Candida tropicalis was developed for the fast detecting of dopamine and epinephrine. Candida tropicalis was immobilized in a carbon paste electrode (CPE) with single wall carbon nanotube (SWCNT). Immobilized cells were used as a origin of the polyphenol oxidase (PPO) to develop voltammetric epinephrine and dopamine biosensor. Voltammetric determination of phenolic compounds such as epinephrine and dopamine a simple technique which is available. Direct oxidation of phenols can be used, but the oxidation potentials of this compounds are similar and they can not be detected distinctively. Another possibility is the use of biosensors based on the polyphenol oxidase (tyrosinase) enzyme that oxidizes the phenolic compounds into their related quinones. By this way, phenolic compounds are epinephrine and dopamine which were used in this study as well detected at different potentials. In this study differential pulse voltammetry and amperometry techniques were used for the determination of dopamine and epinephrine. The effect of varying the amounts of SWCNT and the response of microorganism to epinephrine was investigated to find the optimum composition of the sensor. The effects of pH and temperature were also examined. Increases in biosensor responses obtained by amperometric measurements were linearly related to dopamine concentrations between 0.025 and 0.25 mM and epinephrine concentrations between 0.01 and 0.1 mM. Limits of detection of the biosensor for dopamine and epinephrine were calculated to be 0.008 and 0.0023 mM, respectively. Finally, proposed system was applied to epinephrine and dopamine analysis in pharmaceutical drugs and synthetic serum and the results were compared with LC MS MS method.     

In vitro and in vivo antitumour studies of a new thiosemicarbazide derivative and its complexes with 3d-metal ions

A new ligand, 1-(2-furanthiocarbo)-3-thiosemicarbazide (H₂ftsc), prepared from thiosemicarbazide and carboxymethyl-2-furandithioate, forms complexes [Mn(ftsc)(H₂O)₂], [Pd(ftsc)] · 2H₂O, [M(Hftsc)(acac)₂] (M=Co^III or Cr^III), [M(Hftsc)₂(acac)] (M=Mn^III or Fe^III) and [Zn(Hftsc)₂] · 2H₂O, which were characterized by elemental analyses, magnetic susceptibility, i.r., electronic and n.m.r. spectral data. The Mössbauer spectra of [Fe(Hftsc)₂(acac)] at 298K and 80K suggest the presence of high-spin iron(III) with an S=5/2 state. In vivo and in vitro antitumour activity of the ligand and the complexes have been screened towards several tumour cell-lines.     

Electrochemical Detection of Nitrite in Meat and Water Samples Using a Mesoporous Carbon Ceramic SiO2/C Electrode Modified with In Situ Generated Manganese(II) Phthalocyanine

Mesoporous carbon ceramic SiO₂/50 wt % C (S_BET=170 m² g^?1), where C is graphite, were prepared by the sol‐gel method. The materials were characterized using N₂ sorption isotherms, scanning electron microscopy, and conductivity measurements. The matrix was used as support for the in situ immobilization of Mn(II) phthalocyanine (MnPc) on their surface. XPS was used to determine the Mn/Si atomic ratios of the MnPc‐modified materials. Pressed disk electrodes were prepared with the MnPc‐modified matrix, and tested as an electrochemical sensor for nitrite oxidation. The linear response range, sensitivity, detection limit and quantification limit were 0.79–15.74 µmol L^?1, 17.31 µA L µmol^?1, 0.02 µmol L^?1 and 0.79 µmol L^?1, respectively, obtained using cyclic voltammetry. The repeatability of the proposed sensor, evaluated in terms of relative standard deviation was 1.7 % for 10 measurements of a solution of 12.63 µmol L^?1 nitrite. The sensor employed to determine nitrite in sausage meat, river and lake water samples showed to be a promising tool for this purpose.     

Nitroxide‐Mediated Radical Dispersion Polymerization of Styrene in Supercritical Carbon Dioxide Using a Poly(dimethylsiloxane‐block‐styrene) Alkoxyamine as Initiator and Stabilizer

Summary: Nitroxide‐mediated dispersion polymerization of styrene in supercritical carbon dioxide has been performed successfully at 110 °C using a new polymeric so‐called inistab species, which fulfils the dual functions of an initiator and a colloidal stabilizer. The inistab species comprised a poly(dimethylsiloxane) block and a polystyrene block end‐capped with the nitroxide N‐tert‐N‐butyl‐N‐[1‐diethylphosphono‐(2,2‐dimethylpropyl)] nitroxide (SG1). The dispersion polymerization resulted in sub‐micron sized polymer particles and polymers of narrow polydispersity.

TEM micrograph of PS particles prepared in the dispersion polymerization of S in scCO₂ in the presence of PDMS(\overline M _{\rm n} = 6 500)‐b‐PS(\overline M _{\rm n} = 4 500)‐SG1 at 110 °C.     

In vivo pharmacokinetics of and tissue distribution study of physalin B after intravenous administration in rats by liquid chromatography with tandem mass spectrometry

A rapid and sensitive liquid chromatography tandem mass spectrometry quantitative analysis method was established for the pharmacokinetics and tissue distribution study of physalin B in rat. Physalin B and physalin H (internal standard, IS) were separated on an Agilent Eclips XDB C₈ column. MS detection was performed on a triple quadrupole tandem mass spectrometer in the multiple reaction monitoring mode with a positive eletrospray ionization source. The assay was validated in the concentration ranges of 22.6–22600 ng/mL for heart and lung and 4.52–4520 ng/mL for other tissues. The intra‐ and inter‐day precisions (RSD) were ≤9.23 and ≤12.51%, respectively, with accuracy (%) in the range of 88.07–113.2%. A pharmacokinetic study showed that physalin B has a long dwell time with a half‐life of 321.2 ± 29.5 min and clearance of 175.4 ± 25.7 mL/min/kg after intravenous administration. Additionally, physalin B showed a wide tissue distribution with a special higher penetration in lung. The data presented in this study could provide useful information for the further study of physalin B. Copyright © 2016 John Wiley & Sons, Ltd.     

Bioaccessibility and Oxidative Stability of Omega-3 Fatty Acids in Supplements,Sardines and Enriched Eggs Studied Using a Static In Vitro Gastrointestinal Model

Modern dietary habits have created the need for the design and production of functional foods enriched in bioactive compounds for a healthy lifestyle. However, the fate of many of these bioactive compounds in the human gastrointestinal (GI) tract has not been thoroughly investigated. Thus, in the present study, the bioaccessibility of omega-3 fatty acids was examined. To that end, different foods and supplements underwent simulated digestion following the INFOGEST protocol. The selected samples were foods rich in omega-3 fatty acids both in free and bound form—i.e., dietary fish oil supplements, heat-treated fish, and eggs enriched with omega-3 fatty acids. The oxidation of polyunsaturated fatty acids (PUFAs) was measured at each stage of the digestion process using peroxide value (PV) and TBARS and by quantifying individual omega-3 fatty acids using a gas chromatograph with flame ionization detector (GC-FID). The final bioaccessibility values of omega-3 fatty acids were determined. Changes in the quantity of mono-saturated fatty acids (MUFAs) and saturated fatty acids (SFAs) were recorded as well. The results indicated a profound oxidation of omega-3 fatty acids, giving rise to both primary and secondary oxidation products. Additionally, stomach conditions seemed to exert the most significant effect on the oxidation of PUFAs during digestion, significantly decreasing their bioaccessibility. The oxidation rate of each fatty acid was found to be strongly correlated with its initial concentration. Finally, the oxidation pattern was found to be different for each matrix and emulsified lipids seemed to be better protected than non-emulsified lipids. It is concluded that digestion has a profound negative effect on omega-3 bioaccessibility and therefore there is a need for improved protective mechanisms.     

On-Line Separation and Preconcentration of Trace Metals in Biological Samples Using a Microcolumn Loaded with PAN-Modified Nanometer-Sized Titanium Dioxide,and Their Determination by ICP-AES

A flow injection analysis system incorporating a microcolumn of nanometer-sized TiO₂ loaded with 1-(2-pyridylazo)-2-naphthol (PAN) has been used for the development of an on-line multi-element method for simultaneous separation and preconcentration and subsequent determination of Cu²⁺, Co²⁺, Cr³⁺, Y³⁺, Yb³⁺ and Bi³⁺ by ICP-AES. Effects of pH, sample flow rate and volume, elution conditions, adsorption capacity and interfering ions on analyte recovery were examined. The adsorption capacity of nanometer-sized TiO₂ loaded with PAN was 4.73, 18.57, 3.81, 6.14, 4.52 and 20.35mgg^–1 for Cu²⁺, Cr³⁺, Y³⁺, Yb³⁺, Co²⁺ and Bi³⁺, respectively. The method has been applied to the analysis of trace elements in standard reference biological samples, and the results are in good agreement with the certified values.     

In Vivo Determination of Tetrahydrobiop- terin and Monoamine Neurotransmitters in Rat Brain by Liquid Chromatography with a Nano Crystalline Mn-Doped Lead Dioxide Film Modified Electrode

The fabrication and application of a novel electrochemical detector (ED) with nano crystalline Mn-doped lead dioxide film chemically modified electrode (CME) for liquid chromatography (LC) were described. The Mn-doped PbO₂ film was characterized by scanning tunnel microscope. The electrochemical behaviors of tetrahydrobiopterin, monoamine neurotransmitters and their metabolites at the CME were investigated by cyclic voltammetry and differential pulse voltammetry. It was found that the CME exhibited efficiently electrocatalytic effect on the current response of the seven analytes and the linear ranges of them were over three orders of magnitude with the detection limits being 5.0 × 10^?10 mol L^?1 for tetrahydrobiopterin, 2.5 × 10^?10 mol L^?1 for dopamine, 2.0 × 10^?10 mol L^?1 for norepinephrine, 5.0 × 10^?10 mol L^?1 for serotonin, 4.0 × 10^?10 mol L^?1 for 3,4-dihydroxyphenylacetic acid, 2.0 × 10^?9 mol L^?1 for homovanillic acid, 1.0 × 10^?9 mol L^?1 for 5-hydroxyindoleacetic acid. For its stability, sensitivity, convenience in preparing and long-life of activity, the Mn-doped PbO₂ electrode is therefore suitable for determination of real samples. Coupled with microdialysis sampling, the application of this method for the analysis of tetrahydrobiopterin, monoamine neurotransmitters and their metablites in rat brain was satisfactory.     

Development of a New Voltammetric Methodology for the Determination of Ciprofloxacin in Beef Samples Using a Carbon Paste Electrode Modified with Nafion and Fullerenes

A sensitive, selective, and low cost electrochemical new methodology was developed for the quantification of ciprofloxacin (Cip) in beef samples by cyclic voltammetry and differential pulse voltammetry, using a CPE electrode modified with Nafion and Fullerenes (N−F/CPE). The optimum parameters for the composition of the N−F/CPE electrode are 0.19 g mineral oil, 0.01 g Nafion, 50 μL fullerene, and graphite powder 0.3 g. The electrochemical characterization was carried out by obtaining maximum anodic peak current associated with the oxidation of ciprofloxacin at 1.1 V, where the electrochemical process resulted to be irreversible and diffusion-controlled. The analytical characterization of the proposed methodology was carried out resulting in a LOD of 1.0 μmol L⁻¹, a LOQ of 3.0 μmol L⁻¹, a sensitivity of 0.37±0.006 μA/μmolL⁻¹, and repeatability of 5.38 %.     

Simple and Sensitive Determination of Sibutramine in Slimming Tea Beverages Using a Carbon Screen‐printed Electrode with Adsorptive Stripping Voltammetry

The stimulant sibutramine is an anorexic agent found as an adulterant in natural products and multivitamins supplements used for weight‐loss. In this work, a carbon graphite screen‐printed electrode (SPE‐Gr) with adsorptive stripping pulse differential voltammetry (AdSDPV) is presented for the sensitive and simple detection of sibutramine in slimming tea beverages. The proposed electrochemical method shows a linear working range from 2.0 to 120 μM with a low LOD (0.3 μM) for sibutramine determination in slimming tea samples. The analytical performance of the SPE‐Gr with AdSDPV for sibutramine detection suggests its possible application as an easy, fast and low‐cost method to analyse adulterated tea samples with this stimulant at low levels (<0.1 %).