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571.
A microdetermination of iodide in waters and organic materials is based on oxidation with hydrogen peroxide to iodine which gives a blue colour with o-tolidine at pH 3.5-4.5. The sensitivity is 0.02 mug/ml. 相似文献
572.
Tiberiu?FrentiuEmail author Michaela?Ponta Sorin D.?Anghel Alpar?Simon Ioan?Marginean Emil A.?Cordos 《Mikrochimica acta》2003,143(4):245-254
This paper presents a statistical comparison of Cu, Mn and Zn determinations in biological samples by low power radiofrequency capacitively coupled Ar plasma (275W; 27.12MHz; 0.4Lmin–1 flow rate) atomic emission spectrometry and flame atomic absorption spectrometry using statistical analysis according to the Bland and Altman test and linear regression. For a content (µgg–1 dry mass) of 5-43 Cu, 10-15800 Mn and 8-1100 Zn in fish fillet and freshwater molluscs, there was no significant bias in r.f.CCP-AES for a 95% confidence level. Certified reference materials were analysed by r.f.CCP-AES, and a good agreement between analysis results and certified values was obtained. Matrix effects of Ca and Na and their influence on the detection limits of Cu, Mn and Zn are presented for both methods. As compared to FAAS, r.f.CCP-AES is more prone to interferences and, consequently, the detection limits for Cu, Mn and Zn in biological samples (2; 2 and 3µgg–1 dry mass) are higher than those in FAAS. In spite of these problems, r.f.CCP-AES is capable of accurate and precise analyses of biological samples. 相似文献
573.
Flameless atomic absorption sepctrometry (AAS) has been applied to the investigation of the electroreduction of mercury at the glassy carbon (GC) electrode in dilute mercury(II) solution. The atomic mercury which is produced by electrolysis is found both in the electrolyte solution and on the electrode. The evaporation experiment combined with the flameless AAS clearly shows that mercury(0) deposits on the GC electrode as metallic mercury and adatoms depending strongly on the concentration of mercury(II) in the solution. The monolayer formation and underpotential deposition cannot be observed in the mercury(II)/GC electrode system. 相似文献
574.
Anghel SD Frentiu T Darvasi E Rusu AM Simon A Cordos EA 《Analytical and bioanalytical chemistry》1996,355(3-4):250-251
The excitation temperatures of Ar and Fe, the ionization temperatures of Ar and Ca and the electron number densities have been determined for a radiofrequency capacitively coupled plasma in the tip-ring electrode geometry. The temperatures and the electron number densities possess their maximum value close to the electrodes. 相似文献
575.
Yoshihiro Kitatsuji Zenko Yoshida Hiroshi Kudo Sorin Kihara 《Journal of Electroanalytical Chemistry》2002,520(1-2)
A novel electrochemical method based on controlled-potential electrolysis has been developed for the elucidation of the ion transfer at the interface between two immiscible electrolyte solutions (ITIES). A relationship between the applied interfacial potential (Eapp) and the amount of the ion transferred (Atr) was investigated after an electrolytic equilibrium was attained by controlled-potential electrolysis. The Atr was determined chemically or radiometrically instead of by current measurement. It was found that (i) controlled-potential electrolysis was applicable to the study of the transfer of such hydrophilic ions as transition metal ions which gave no appreciable current within the potential window in voltammetry or polarography at ITIES, (ii) controlled-potential electrolysis in combination with a sensitive analytical method enabled a study of the transfer reaction of an ion of very dilute concentration, and (iii) even when the transfer reaction of an ion was irreversible or quasi-reversible, a standard ion transfer potential could be determined by controlled-potential electrolysis without using a kinetic parameter. The controlled-potential electrolysis method developed was applied to the transfer reactions of actinide ions such as UO2 2+ and Am3+ from aqueous solution to nitrobenzene solution in the absence or presence of an ionophore facilitating the transfer. The Gibbs energy for the transfer of actinide ion and a stability constant of the complex between an actinide ion and the ionophore in nitrobenzene solution were determined from log D versus Eapp plots (D the ratio of the concentration of the ion in nitrobenzene solution to that in aqueous solution). The feasibility of controlled-potential electrolysis as a method for electrolytic separation of actinide ions is discussed. 相似文献
576.
Yoshiki Sohrin Kenji Isshiki Eiichiro Nakayama Sorin Kihara Masakazu Matsui 《Analytica chimica acta》1989
The simultaneous determination of tungsten and molybdenum in sea water is based on preconcentration by column extraction with 7-(1-vinyl-3,3,5,5-tetramethylhexyl)-8-quinolinol (Kelex- 100) resin, and measurement of the polarographic catalytic currents obtained in a solution of chlorate, benzilic acid and 2-methyl-8-quinolinol. When the concentration factor is 50, the detection limits are 2.4 pM for tungsten and 17 pM for molybdenum (for a signal-to-noise ratio of 3). The precision of the determination is ca. 10% for 67 pM tungsten and ca. 5% for 106 nM molybdenum in sea water (n=4). Results for sea water and other natural waters are presented. 相似文献
577.
Some inequalities for Fourier coefficients in inner product spaces and related results are given. These inequalities complement, in a sense, some of the results in a recent book due to Mitrinovi, Peari and Fink.This research was supported by a grant from La Trobe University 相似文献
578.
Brandon Lindley Eddie Lee Howell Breannan D. Smith Gregory J. Rubinstein M. Gregory Forest Sorin M. Mitran David B. Hill Richard Superfine 《ournal of non Newtonian Fluid Mechanics》2009,156(1-2):112-120
We revisit a classical topic: response functions of viscoelastic layers in large amplitude oscillatory shear. Motivated by questions concerning protective biological layers, we focus on boundary stresses in a parallel plate geometry with imposed oscillatory strain or stress. These features are gleaned from resolution and analysis of coupled standing waves of deformation and stress. We identify a robust non-monotone variation in boundary stress signals with respect to all experimental controls: viscoelastic moduli of the layer, layer thickness, and driving frequency. This structure of peaks and valleys in boundary values of shear and normal stress indicates redundant mechanisms for stress communication (by tuning to the peaks) and stress filtering (by tuning to the valleys). In this paper, we first restrict to a single-mode non-linear Maxwell model for the viscoelastic layer, where analysis renders a transparent explanation of the phenomena. We then consider a Giesekus constitutive model of the layer, where analysis is supplanted by numerical simulations of coupled non-linear partial differential equations. Parametric studies of wall stress values from standing waves confirm persistence of the Maxwell model phenomena. The analysis and simulations rely on and extend our recent studies of shear waves in a micro parallel plate rheometer [S.M. Mitran, M.G. Forest, L. Yao, B. Lindley, D. Hill, Extenstions of the Ferry shear wave model for active linear and nonlinear microrheology, J. Non-Newtonian Fluid Mech. 154 (2008) 120–135; D.B. Hill, B. Lindley, M.G. Forest, S.M. Mitran, R. Superfine, Experimental and modeling protocols from a micro-parallel plate rheometer, UNC Preprint, 2008]. 相似文献
579.
Sorin Ivanovici Michael Puchberger Helmut Fric Guido Kickelbick 《Monatshefte für Chemie / Chemical Monthly》2007,138(6):529-539
Summary. Metal-alkoxides containing polymerizable groups are regularly used as precursors for inorganic–organic hybrid materials applying
the combination of the sol–gel process and organic polymerizations. Here we report the synthesis of acetoacetoxy derivatives
that are linked to methacrylate groups via alkyl chains of different chain length. The coordination of the resulting molecules to titanium- and zirconium-alkoxides
(M(OR)4; M = Ti, Zr; R = ethyl, butyl, isopropyl) was investigated applying NMR and FT-IR measurements. The results were related to structural data
of the dinuclear complex [Ti(O
i
Pr)3(EAA)]2 (HEAA: ethyl acetoacetate) which was obtained by single crystal X-ray diffraction. The study revealed that the β-keto ester groups
acted as chelating ligands in all cases and thus polymerizable coordination compounds were formed. However, NMR analyses in
solution showed that transesterification of the methacrylic-type monomers occurred even at mild conditions as a side reaction
in a ratio which was found to be dependent on the type of metal alkoxide used. 相似文献
580.
We study the asymptotics of the Stokes problem in cylinders becoming unbounded in the direction of their axis. First we assume that the applied forces are independent of the axis coordinate, then we assume that they are periodic along the axis of the cylinder. Finally in Section 4, we make an asymptotic analysis under much more general assumptions on the applied forces. 相似文献