Electrocatalytic Determination of Histamine on a Nickel‐Film Glassy Carbon Electrode

The electrocatalysed oxidation of histamine on a thin film nickel electrode was investigated for the purpose of its chronopotentiometric determination. The oxidation mechanism implies complex and combined processes of histamine physical adsorption and consequent oxidation via joined oxidation potency of a constant current and electrochemically generated nickel‐oxihydroxide, which played a role of an electron transfer catalyst. Experimental parameters affecting the oxidation process, including type and concentration of supporting electrolyte, initial potential, oxidation current, temperature and concentration time, were optimised. Using a 240 s accumulation time, limit of detection and quantitation were 0.11 mg L^?1 and 0.29 mg L^?1 of histamine, respectively.     

Testing of the influenza virus purification by CIEF

In virological practice, the pre‐concentration, purification and subsequent determination of the purity and concentration of the viruses from the cultural medium and/or from the real sample are required. The conventional techniques used today are equipment demanding, time‐consuming and laborious. In this study, the CIEF of influenza viruses with UV detection has been developed and subsequently used to test the purification of the virus from the biological samples. The equine and swine influenza viruses present in infected allantoic fluid of specific pathogen free embryonated chicken eggs were precipitated by using PEG 6000 and sodium chloride. The precipitated viruses were centrifuged at 14 000×g, and the impurities of different densities were removed by using the sucrose gradients. The efficiency of the virus purification technique was examined by the CIEF and compared to the results of real‐time PCR. The pIs of both influenza viruses were determined. Simultaneously, the CIEF was found to be a suitable method for the rapid testing of the efficiency of the virus purification.     

Quantification of methane in humid air and exhaled breath using selected ion flow tube mass spectrometry

In selected ion flow tube mass spectrometry, SIFT‐MS, analyses of humid air and breath, it is essential to consider and account for the influence of water vapour in the media, which can be profound for the analysis of some compounds, including H₂CO, H₂S and notably CO₂. To date, the analysis of methane has not been considered, since it is known to be unreactive with H₃O⁺ and NO⁺, the most important precursor ions for SIFT‐MS analyses, and it reacts only slowly with the other available precursor ion, O. However, we have now experimentally investigated methane analysis and report that it can be quantified in both air and exhaled breath by exploiting the slow O/CH₄ reaction that produces CH₃O ions. We show that the ion chemistry is significantly influenced by the presence of water vapour in the sample, which must be quantified if accurate analyses are to be performed. Thus, we have carried out a study of the loss rate of the CH₃O analytical ion as a function of sample humidity and deduced an appropriate kinetics library entry that provides an accurate analysis of methane in air and breath by SIFT‐MS. However, the associated limit of detection is rather high, at 0.2 parts‐per‐million, ppm. We then measured the methane levels, together with acetone levels, in the exhaled breath of 75 volunteers, all within a period of 3 h, which shows the remarkable sample throughput rate possible with SIFT‐MS. The mean methane level in ambient air is seen to be 2 ppm with little spread and that in exhaled breath is 6 ppm, ranging from near‐ambient levels to 30 ppm, with no significant variation with age and gender. Methane can now be included in the wide ranging analyses of exhaled breath that are currently being carried out using SIFT‐MS. Copyright © 2010 John Wiley & Sons, Ltd.     

The preparation of tetracyanonickelates showing electrical conductivity

The tetracyanonickelates Ni(NH₃)₂Ni(CN)₄·1.9 H₂O (1), Ni(NH₃)_1.65(C₄H₈O₂)_0.2Ni(CN)₄·0.8 C₄H₈O₂·0.35 H₂O (2) and Ni(en)₃Ni(CN)₄·H₂O (3) exhibit, after contact with a solution of iodine (I₂/KI), appreciable weight gains. According to thermal analysis, IR spectra and chemical analysis the new products contain intercalated iodine and iodides with the highest iodine content found in the product formed from (3). The results of high frequency conductance measurements of this product showed the highest value of electrical conductivity (10^–6 S cm^–1). Other compounds show relatively low values of (10^–8–10^–11 S cm^–1).The iodine together with its iodide and polyiodide forms enters host (3) as an intercalated species. The iodide and polyiodide forms are formed during the initial redox reactions between the NH group of the ethylenediamine and the iodine.     

High-temperature oxidation of FeCrAl alloy with alumina–silica–ceria coatings deposited by sol–gel method

One-layer protective coatings made up of SiO₂–Al₂O₃ or SiO₂–Al₂O₃–CeO₂ oxides were synthesized on a FeCrAl alloy substrate by the sol–gel method from sols containing tetraethyl orthosilicate, aluminum tri-sec-butoxide and cerium(III) 2,4-pentanedionate as the precursors. Coating solutions with the Si:Al:Ce molar ratio of 3:1:0, 3:1:0.1; 3:1:0.01, and 3:1:0.001 were used. The composition and morphology of the obtained gels were examined by TG/DSC, XRD, and SEM techniques. It was found that a small addition of cerium affected the morphology of the forming coatings and improved the FeCrAl alloy resistance to high-temperature oxidation (in air at T = 900 °C for t = 100 h). The oxidation of all the investigated samples conformed to the parabolic rate. The protection effectiveness of the one-layer coatings after 100 h of high-temperature oxidation was as high as 70 %.     

Functionalised Microgels for Acrylic Coatings

Summary: Aqueous acrylic dispersions of hydroxy-functionalised copolymer microgel particles crosslinked with allyl methacrylate were synthesized by emulsion polymerization. The microgels were investigated as reactive polymer fillers in mixtures with a water-borne film-forming dispersion. Properties of coatings cast from mixtures of aqueous dispersion of hard microgel particles and film-forming water-borne dispersion were investigated. The swelling behaviour of microgels in selected solvents (aliphatic ketones) as a function of microgel composition is discussed as well. It was found that the swelling ability of microgels decreased with growing degree of crosslinking. Microgels comprising copolymerised butyl methacrylate swelled less in aliphatic ketones than microgels without this comonomer. This work was focused mainly on the influence of microgels incorporated in the commercial solvent-borne acrylic binders on the properties of coatings. It was shown that the application of microgels that were redispersed in acetone did not affect the surface appearance and transparency of coatings. Moreover, the presence of microgel network precursors accelerated film curing at ambient temperature and improved the final hardness of coatings.     

Voltammetric Determination of 4‐Nitrophenol Using a Novel Type of Silver Amalgam Paste Electrode

A differential pulse voltammetric (DPV) method was developed for the determination of 4‐nitrophenol (4‐NP) at a newly developed silver amalgam paste electrode (AgA‐PE) in Britton–Robinson buffer pH 3.0. The electrode is based on a disposable plastic pipette tip filled with paste amalgam based on a mixture of mercury and fine silver powder (9 : 1, w/w). The experimental parameters, such as pH of Britton–Robinson buffer and activation and regeneration potential of the electrode surface were optimized. The reduction peak current dependences were linear for the concentration of 4‐NP from 0.2 to 100 μM. The method showed reproducible results with RSD (n=45) of 1.7%. The limit of determination (LOD) was 0.3 μM. The method was successfully applied for the direct determination of 4‐NP in drinking water.     

Molecular and crystal structure of 5-phenyl, 5-m-nitrophenyl,and 5-spirocyclopentane derivatives of 3-amino-2,4,4-tricyanobicyclo [4,4,0] deca-2,10-diene

To examine the ability of 3-amino-2,4,4-tricyanobicyclo[4,4,0]deca-2,10-dienes (I) to form dimeric associates, we have investigated molecular and crystal structure of three derivatives of (I): 5-phenyl (II), 5-m-nitrophenyl (III), and 5-spirocyclopentano (IV). Hydrogen bonding via the aminonitrile fragment leads to formation of centrosymmetric dimeric associates in compounds (II, III) and a chain structure in (IV). Crystal data for (II): space group P2₁/c, a=8.726(3), b=15.879(5), c=15.597(5) Å, α=γ=90, β=105.13(2)⁰, V=2086.2 ų, Z=4, R=0.093; for (III): space group C2/c, a=24.725(8), b=9.004(5), c=24.391(8) Å, α=γ=90, β=125.36(2)⁰, V=4428.2ų, Z=8, R=0.080; for (IV): space group C2/c, a=24.443(8), b=10.240(5), c=16.645(6) Å, α=γ=90, β=108.89(2)⁰, V=3941.8 ų, Z=8, R=0.089.