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71.
Keith B. Male John H. T. Luong Michael Trani 《Applied biochemistry and biotechnology》1994,44(1):91-100
Water-soluble 2-hydroxypropyl-β-cyclodextrin (Hp-β-CyD), a cyclic and nonreducing oligosaccharide was used to enclose a hydrophobic guest molecule 1,1′-dimethylferrocene (DMF) to form a water-soluble yellow complex. At high concentrations (300 mM), Hp-β-CyD enclosed up to 100 mM DMF. The yellow complex was electrochemically oxidized (platinum vs Ag/AgCl poised at +450 mV) to form a blue dye, 1,1′-dimethylferricinium (DMF+). This is a one-electron transfer process and the ferricinium cation formed exhibited an absorption peak at 650 nm. The concentrated DMF+ was stable for at least 4 mo at 4°C and insensitive to a wide pH variation (pH 2–11). Application of the novel DMF+ complex as a colorimetric dye for the determination of uric acid in urine was successfully demonstrated. The reaction between the dye and uric acid is almost instantaneous and decrease in absorbance caused by the reduction of 1,1′-dimethylferricinium to 1,1′-dimethylferrocene can be followed at 650 nm. The results obtained agreed well with those of the reference reversed-phase HPLC method. 相似文献
72.
Electrophoretic separation of aniline derivatives using fused silica capillaries coated with acid treated single-walled carbon nanotubes 总被引:1,自引:0,他引:1
This paper reports on a new strategy for coating fused silica capillaries based on the ionic adsorption of acid treated single-walled carbon nanotubes (SWCNTs) on a poly(diallydimethylammonium chloride)-modified fused silica surface. The coated capillaries were used to demonstrate their performance for baseline separation of a mixture of seven nitrogen-containing aromatic compounds compared to capillary zone electrophoresis. This combined layer formed a coating material that could be useful for improvement of the selectivity of the solutes in an electrical field. We reasoned that the interaction of the solutes and the modified capillary wall occurred mainly via ionic interactions with the charged moieties of CNTs. The single-walled CNT modified capillaries were very stable and could be used for over 200 repeated analyses without compromising its analytical performance. 相似文献
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The volumes of mixing for the systems cyclopentane + cyclohexane, cyclopentane + cycloheptane, cyclohexane + cycloheptane (at 20°C), and cyclopentane + cyclooctane, cyclohexane + cyclooctane, cycloheptane + cyclooctane (at 30 °C) have been measured with a dilatometer. All systems show volume contractions, except the first. The energies of mixing are also given. They vary from 7 to 55 J/mol for equimolar solutions. 相似文献
75.
Sylvestre JP Kabashin AV Sacher E Meunier M Luong JH 《Journal of the American Chemical Society》2004,126(23):7176-7177
Femtosecond laser radiation has been used to ablate a gold target in aqueous beta-cyclodextrin (CD) solutions to produce stable gold nanoparticle colloids with extremely small size (2 to 2.4 nm) and size dispersion (1 to 1.5 nm). On the basis of XPS and zeta-potential measurements, we propose a model involving chemical interactions between the gold and the CDs. The model includes both the hydrophobic interaction of the Au0 with the interior cavity of the CD and the hydrogen bonding of O- groups on the partially oxidized gold surface with -OH groups of the CDs. 相似文献
76.
Nguyen Canh Luong 《Advances in Applied Clifford Algebras》2001,11(2):171-180
The factorization of the Laplacian by means of first order systems and of second order operators was considered by several
authors (see, e.g [2],[3],[4]).
In the paper the definition of Cauchy-Riemann system (CR-system) of ordern is given by their symbols.
We prove that ifD
(n) is the symbol andD
(s, n) is the sign-matrix of CR-system, then
and
where Δ denotes teh Laplacian operator inR
n. We show that(CN)
n ≠ ϕ if and only ifn ∈ {2, 4, 8}.
This work was supported in part by N.B.R.P in N.S. Vietnam 相似文献
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