Search results for "Roche"
showing 10 items of 2666 documents
Simultaneous Determination of Adrenaline and Noradrenaline by First Derivative Spectrophotometry in a Fia Assembly
1996
Abstract This article deals with the design of an unsegmented-flow injection manifold for the simultaneous determination of adrenaline and noradrenaline two structurally related compounds with overlapping spectra. An FIA manifold is proposed for the simultaneous determination in which the sample solution is directly injected into a carrier-reagent stream of aqueous NaOH. The selected wavelengths (first derivative) were 394 and 342 nm, for noradrenaline and adrenaline, respectively with an integration time of 0.4 s. The calibration graphs are linear over the range 2.0–30 ppm for both drugs. The method is applied to different synthetic mixtures of both drugs.
On the Existence of Different Zeolite-Associated Topological Redox Isomers. Electrochemistry of the Y Zeolite-Associated Mn(Salen)N3 Complex
2002
The electrochemical properties of Y zeolite-associated MnIII(salen)N3 (salen = trans-(R,R)-1,2-bis(salicyldeneamino)cyclohexane) has been investigated using polymer film electrodes immersed into neutral aqueous solutions. Zeolite Y-associated Mn(III)−salen complexes are reduced in one-electron reversible process at −0.25 V versus SCE. The electrochemical response is discussed in terms of the existence of two topological redox isomers: a weakly boundary-associated Mn(salen) complex, whose electrochemical response corresponds to a reversible one-electron transfer controlled by diffusion of the positive ions of the supporting electrolyte through the zeolite surface windows and channels, and a…
Heat Capacity of Transfer of (Ethylene oxide)13-(propylene oxide)30-(ethylene oxide)13 from Water to the Aqueous Anionic Surfactant Solutions at 298 …
2004
Heat capacities of transfer (ACpt) of unimeric (ethylene oxide)(13)-(propylene oxide)(30)-(ethylene oxide)(13) from water to the aqueous surfactant solutions as functions of the surfactant concentrations (m(S)) were determined at 298 K. The surfactants investigated are sodium hexanoate, sodium heptanoate, sodium octanoate, sodium undecanoate, and sodium dodecanoate. For short alkyl chain surfactants, the profiles of the DeltaCp(t) versus ms curves show maxima and minima; for long alkyl chain surfactants, the maximum becomes sharper and moved to lower ms values whereas the minimum tends to disappear. These experimental trends are different from those of the enthalpy in agreement with the fac…
Aqueous nonionic copolymer-functionalized laponite clay. A thermodynamic and spectrophotometric study to characterize its behavior toward an organic …
2006
The affinity of functionalized Laponite clay toward an organic material in the aqueous phase was explored. Functionalization was performed by using triblock copolymers based on ethylene oxide (EO) and propylene oxide (PO) units that are EO(11)PO(16)EO(11) (L35) and PO(8)EO(23)PO(8) (10R5). Phenol (PhOH) was chosen as organic compound, which represents a contaminant prototype. To this purpose, densities and enthalpies of mixing as well as PhOH UV-absorption spectra were determined. The enthalpy and the spectrophotometry revealed PhOH-Laponite interactions whereas the volume did not. It emerged that the area occupied by PhOH on the Laponite surface is equal to that computed from the partial m…
Proton Transfer versus Hydrogen Bonding: The Reduction of Ubiquinone Q2Incorporated in a Self-Assembled Monolayer in Unbuffered Aqueous Solution
2014
The electrochemical reduction of ubiquinone Q2 (UQ2) in unbuffered aqueous media was investigated over a pH range of 2 to 11, and the results were compared to those obtained in our previous work in buffered solutions. The short isoprene chains of UQ2 were incorporated in a self-assembled monolayer. Analysis of the mechanism and a study in D2O solutions allowed us to demonstrate the important role of hydrogen bonding in the stabilization of the reduced species, also in water. If the concentration of H+ is low relative to that of the quinone, the electrochemical reaction does not proceed through proton-coupled electron transfer, as it does in buffered medium or at low pH values (pH<4.4). We p…
Electrochemically assisted anion insertion in Au(I)–Cu(I) heterotrimetallic clusters bearing ferrocenyl groups: Application to the fluoride/chloride …
2010
The heterotrimetallic Au(I)–Cu(I) aggregate [{Au3Cu2(C2C6H4Fc)6}Au3(PPh2C6H4PPh2)3](PF6)2 exhibits a well-defined solid state electrochemistry in contact with aqueous media, based on ferrocenyl-centred oxidation processes involving anion insertion. Upon attachment of microparticulate deposits of the cluster to graphite electrodes, distinctive electrochemical responses can be obtained for fluoride and chloride ions in aqueous media. Keywords: Heterometallic clusters, Gold, Copper, Fluoride/chloride discrimination, Electrochemical anion insertion
Study of Redox Processes in Zeolite Y-Associated 2,4,6-Triphenylthiopyrylium Ion by Square Wave Voltammetry
2003
The electrochemical responses of 2,4,6-triphenylthiopyrylium ion (TTP+) in solution and attached to zeolite Y (TTP@Y) are described using cyclic and square wave voltammetries upon immersion of zeolite-modified polymer film electrodes in MeCN (LiClO4, Et4NClO4, and BuN4PF6 electrolytes) and aqueous (LiNO3, NaNO3, and KNO3 electrolytes) media. The electrochemistry of TTP@Y in contact with Bu4NPF6/MeCN is identical to that of TTP(BF4) in solution, with reduction processes at −0.25, −0.74, and −1.36 V vs SCE, and oxidation steps at +0.85 and +1.11 V. This response differs from those obtained for TTP@Y in Et4NClO4/MeCN and LiClO4/MeCN electrolytes. In contact with aqueous electrolytes, TTP@Y dis…
Ionic partition diagram of tetraphenylporphyrin at the water|1,2-dichloroethane interface
2011
diagram of 5,10,15,20-tetraphenyl-21H,23H-porphine (H2TPP) at the water|1,2-dichloroethane interface using a simple Born solvation model. This zone diagram shows under which form this porphyrin is present, i.e. neutral, monoprotonated or diprotonated, and in which phase i.e. either in the aqueous or the organic phase as a function of the aqueous pH and the interface polarisation that can be controlled externally or by the distribution of supporting electrolytes. This diagram explains why the monoprotonated form has been difficult to observe when doing biphasic pH titrations
Electrochemistry of copper complexes with macrocyclic polyamines containing pyrazole units.
2006
The voltammetric behaviour of bi- and mono-nuclear complexes formed in solution by Cu(2+) with three polyazacyclophanes containing pyrazole units in aqueous solution is described. Cyclic and square wave voltammetric responses at glassy carbon electrodes indicate that the reduction of copper-macrocycle complexes in solution takes place in two successive one-electron per Cu transfer processes coupled with preorganization and protonation reactions that mimic the behaviour of superoxide dismutase. The electrochemistry of ternary Cu(2+)-receptor-dopamine complexes exhibits significant differences with respect to the protection of the neurotransmitter from post-electron transfer cyclization react…
GROWTH AND PHOTOELECTROCHEMICAL BEHAVIOUR OF ELECTRODEPOSITED ZnO THIN FILMS FOR SOLAR CELLS
2012
Thin zinc oxide films were deposited potentiostatically from zinc nitrate aqueous solutions on ITO substrates. The influence of experimental parameters (temperature, electrolyte concentration, deposition potential) on structure and morphology of films was investigated. Deposited films were generally polycrystalline in structure, even if growth according to preferential planes occurs in certain conditions. The effect of thermal treatments in air at 150 and 350 °C was also studied. In some cases, Cl species were incorporated into deposit by adding zinc chloride to the electrolyte. A photoelectrochemical investigation, performed in neutral solution before and after thermal treatment, gives mor…