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1.
Bhagat PR Pandey AK Acharya R Natarajan V Rajurkar NS Reddy AV 《Analytical and bioanalytical chemistry》2008,391(3):1081-1089
A molecular iodine selective membrane has been used for preconcentration of I2 generated in situ by iodometric reaction of with excess I− in acidic medium (pH 1–2). This iodometric reaction amplifies the iodine content six times resulting in enhancement of analytical
response ranging from three times for molecular methods to six times for elemental methods. The chemical conditions of this
iodometric reaction were optimized for quantitative generation and subsequent sorption of I2 in the membrane samples (96 ± 3%). The homogeneous transparent membrane was prepared by immobilizing I2-complexing polyvinylpyrrolidone (PVP) in the plasticized cellulose triacetate matrix. Four different analytical methods were
examined for quantitative determination of in iodized salt samples by preconcentrating it as I2 in the membrane matrix. These methods were: (1) spectrophotometry of the PVP-I2 complex formed in the membrane matrix, (2) a radiotracer method using I− tagged with 131I radiotracer, (3) instrumental neutron activation analysis (INAA), and (4) energy-dispersive X-ray fluorescence (EDXRF) analysis.
The contents thus determined in the iodized salt samples by the membrane-based radiotracer method were compared with the total
iodine determined in salt samples by epithermal instrumental neutron activation analysis (EINAA). The membrane-based method
for iodate determination in salt samples has advantages over conventional analytical methods, for example preconcentration
and chemical amplification, and is free from interference from anions.
Figure A molecular iodine selective membrane was used for the quantitative preconcentration of I2 generated in situ by iodometric reaction of with excess Iaˆ’ in acidic medium, which amplifies iodine content six times 相似文献
2.
New far-visible absorbing anilino-cyanine dyes have been synthesised for future application as chromoionophores in integrated
waveguide absorbance optodes based on bulk optodes. The effect of the heterocycle, of the substitution of the heterocyclic
nitrogen and of the type of heptamethine central ring on the pK
a
values (4.3–8.2 in ethanol–water solutions and 9.5–11.0 in plasticised PVC membranes), on the spectroscopic characteristics
of the dye and on photostability is discussed. pH-selective bulk optodes have been formulated as a first approach to develop
ion-selective optodes, and sensitivity, repeatability, lifetime and response time have been determined. The dyes show good
analytical behaviour for use as chromoionophores for the development of ion-selective optodes. Reversible (80–87%), fast (tr90% = 0.94–2.28 min) and pH-sensitive membranes (slopes of 0.09–0.23 ΔAbs·pHdec–1, absorbance range 0.19–0.53) have been obtained. Moreover, they exhibit good spectroscopic features for employment with integrated
optochemical sensors: absorption maxima of the acidic species in plasticised PVC membranes matched those of 650–670-nm LEDs,
high molar absorption coefficients ( L mol–1 cm–1 and L mol−1 cm−1) and fluorescence.
Absorption spectra of the acidic and basic structures of one of the synthesised chromoionophores at different pKa values.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
3.
Richard D. Adams Burjor Captain Wei Fu Mark D. Smith Lei Zhu 《Journal of Cluster Science》2006,17(1):87-95
Two new compounds Pd2Os3(CO)12
, 13 and Pd3Os3(CO)12
, 14 have been obtained from the reaction of
with Os3(CO)12 at room temperature. The products were formed by the addition of two and three
groups to the Os–Os bonds of Os3(CO)12. Compounds 13 and 14 interconvert between themselves by intermolecular exchange of the
groups in solution. Compounds 13 and 14 have been characterized by single crystal X-ray diffraction analyses.Dedicated to Professor Brian F. G. Johnson on the occasion of his retirement – 2005. 相似文献
4.
François Quentel Valentin Mirčeski Maurice L’Her 《Journal of Solid State Electrochemistry》2008,12(1):31-39
Thermodynamics and kinetics of hydrophilic ion transfers across water|n-octanol (W|OCT) interface have been electrochemically studied by means of novel three-phase and thin-film electrodes. Three-phase
electrodes used for thermodynamics measurements comprise edge plane pyrolytic graphite, the surface of which was partly modified
with an ultrathin film of OCT, containing hydrophobic lutetium bis(tetra-tert-butylphthalocyaninato) (Lu[tBu4Pc]2) as a redox probe. The transfers of anions and cations from W to OCT were electrochemically driven by reversible redox transformations
of Lu[tBu4Pc]2 to chemically stable lipophilic monovalent cation and anion , respectively. Upon reduction of Lu[tBu4Pc]2, the transfers of alkali metal cations from W to OCT have been studied for the first time, enabling estimation of their Gibbs
transfer energies. For kinetic measurements, a thin-film electrode configuration has been used, consisting of the same electrode
covered completely with a thin layer of OCT that contained the redox probe and a suitable electrolyte. Combining the fast
and sensitive square-wave voltammetry with thin-film electrodes, the kinetics of , , and Cl− transfers have been estimated.
Dedicated to Professor Dr. Yakov I. Tur’yan on the occasion of his 85th birthday. 相似文献
5.
Reinaldo F. Teófilo Helder J. Ceragioli Alfredo C. Peterlevitz Leonardo M. Da Silva Flavio S. Damos Márcia M. C. Ferreira Vitor Baranauskas Lauro T. Kubota 《Journal of Solid State Electrochemistry》2007,11(10):1449-1457
The electrochemical properties of boron-doped diamond (BDD) polycrystalline films grown on tungsten wire substrates using
ethanol as a precursor are described. The results obtained show that the use of ethanol improves the electrochemistry properties
of “as-grown” BDD, as it minimizes the graphitic phase upon the surface of BDD, during the growth process. The BDD electrodes
were characterized by Raman spectroscopy, scanning electronic microscopy, cyclic voltammetry (CV), and electrochemical impedance
spectroscopy (EIS). The boron-doping levels of the films were estimated to be ∼1020 B/cm3. The electrochemical behavior was evaluated using the and redox couples and dopamine. Apparent heterogeneous electro-transfer rate constants were determined for these redox systems using the CV and EIS techniques. values in the range of 0.01–0.1 cm s−1 were observed for the and redox couples, while in the special case of dopamine, a lower value of 10−5 cm s−1 was found. The obtained results showed that the use of CH3CH2OH (ethanol) as a carbon source constitutes a promising alternative for manufacturing BDD electrodes for electroanalytical
applications. 相似文献
6.
Kinetics and equilibria for the formation of a 1:1 complex between palladium(II) and chloroacetate were studied by spectrophotometric measurements in 1.00 mol HClO4 at 298.2 K. The equilibrium constant, K, of the reaction
was determined from multi-wavelength absorbance measurements of equilibrated solutions at variable temperatures as log 0.006 with and , and spectra of individual species were calculated. Variable-temperature kinetic measurements gave rate constants for the forward and backward reactions at 298.2 K and ionic strength 1.00 mol as and , with activation parameters and , respectively. From the kinetics of the forward and reverse processes, and were derived in good agreement with the results of the equilibrium measurements. Specific Ion Interaction Theory was employed for determination of thermodynamic equilibrium constants for the protonation of chloroacetate () and formation of the PdL+ complex (). Specific ion interaction coefficients were derived. 相似文献
7.
The aluminium alloy Al-12Si has been polarized by potentiodynamic method at 25 °C under magnetic stirring and in an aerated
solution. Its electrochemical behaviour was tested first by varying the concentration of NaI or NaCl (10−4, 10−3, 10−2) added respectively to NaCl or NaI (10−3 M), and the pH of NaCl 10−3 M (pH = 2.3, 7.3, 10) when adding HCl or NaOH (i.e. the composition of the solution), then by incorporating different ions
familiar to an industrial atmosphere (Cu2+, Zn2+, , , ) at 10−6 M to NaCl 10−3 M (i.e. the electrolyte nature). The use of the electrokinetic curves obtained allowed the access to the passivation (i
pass
, E
rup
and E
rep
) and to the electrokinetic parameters (i
corr
, R
p
and P). They prove the behaviour dependence of the above alloy on the composition and nature of the electrolyte. 相似文献
8.
The energy of a graph is defined as the sum of the absolute values of all the eigenvalues of the graph. Let
denote the set of trees on n vertices and diameter d,
. Yan and Ye [Appl. Math. Lett. 18 (2005) 1046–1052] have recently determined the unique tree in
with minimal energy. In this article, the trees in
with second-minimal energy are characterizedAMS Subject Classification: 05C50, 05C35 相似文献
9.
Reena Singh Atanu Banerjee Yee Gordon Kajal Krishna Rajak 《Transition Metal Chemistry》2009,34(6):689-694
Abstract The title complexes and have been synthesized in excellent yields by reacting Co(OAc)2·4H2O with H2L1 and H2L2, respectively, in acetonitrile solution. Here, [L1]2− and [L2]2− are the deprotonated forms of N,N-bis(2-hydroxybenzyl)-N′,N′-dimethylethylenediamine and N,N-bis(2-hydroxybenzyl)-2-picolylamine, respectively. The crystal structures of and were determined by x-ray crystallography. In , each cobalt atom has distorted trigonal bipyramid geometry, while in , each cobalt atom has distorted octahedral geometry. Variable temperature magnetic moment measurements show weak antiferromagnetic
interaction in . The magnetic characterization for is in agreement with the presence of Co(II) and Co(III) centers.
Graphical Abstract The title complexes and have been synthesized in excellent yields by reacting Co(OAc)2·4H2O with dianionic N2O2 coordinating ligands. In complex 1, each cobalt atom has distorted trigonal bipyramid geometry, while in complex 2, each
cobalt atom has distorted octahedral geometry. Variable temperature magnetic moment measurements show weak antiferromagnetic
interaction in complex 1. The magnetic characterization for complex 2 is in agreement with the presence of Co(II) and Co(III)
centers.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
10.
A chemiluminescent (CL) detection method has been developed for DNA hybridization. The assay relies on a sandwich-type DNA
hybridization in which gold nanoparticles modified with alkylthiol-capped oligonucleotide strands are used as probes to monitor
the presence of the specific target DNA. The , which is the dissolving product of the gold nanoparticles anchored on the DNA hybrids, serves as an analyte in the H2O2–luminol– CL reaction for the indirect measurement of the target DNA. The combination of the remarkable sensitivity of the CL analysis
with the large number of released from each DNA hybrid allows a detection limit at levels as low as 0.1 pM of the target DNA. Moreover, with a further
silver amplification step, the detection limit will be pushed down to the femtomolar domain.
相似文献
11.
Miyamoto A Nakamura K Kishikawa N Ohba Y Nakashima K Kuroda N 《Analytical and bioanalytical chemistry》2007,388(8):1809-1814
A method that combines sequential injection analysis (SIA), flow injection analysis and chemiluminescence (CL) detection was
developed for the quasi-simultaneous determination of antioxidative activities against superoxide anion and nitric oxide (NO). The antioxidative activity was expressed as the decrease in luminol CL intensity caused by the quenching
of or NO by an antioxidant. The SIA system consisted of two syringe pumps, two selection valves, two holding coils, an HPLC
pump to deliver luminol solution, and a CL detector. Operation of the syringe pumps and multiport valves was controlled automatically
using a personal computer with appropriate software. A hypoxanthine (HX)-xanthine oxidase (XOD) system was used for the generation
of , and (±)-(E)-4-methyl-2-[(E)-hydroxyimino]-5-nitro-6-methoxy-3-hexenamide (NOR1) was employed as NO donor agent. The repeatability of the method was
evaluated with 35.2 μg ml−1
L-ascorbic acid, and the relative standard deviations (RSD) of the antioxidative activities were less than 3.8%. The quasi-simultaneous
determination of the antioxidative activities in one sample was completed within 2.0 min. The antioxidative activities of
some antioxidants and commercially available supplements containing certain antioxidants were successfully determined using
this system. The proposed system is rapid and reproducible, and thus may be useful for the screening of functional foods,
supplements and pharmaceutical formulations that exhibit antioxidative activity.
Figure The system that utilizes a combination of SIA and FIA with CL for the quasi-simultaneous determination of antioxidative activity
against a NO and b
. SP1, 2: syringe pump, HC1, 2: holding coil, MV1, 2: multi-port valve, P: pump, D: chemiluminescence detector, I: integrator, M1, 2: mixing tee, NOR1: (±)-(E)-4-methyl-2-[(E)- hydroxyimino]-5-nitro-6-methoxy-3-hexenamide, HX: hypoxanthine, XOD: xanthine oxidase. 相似文献
12.
Anwar Ali Mohd Tariq Rajan Patel Firdoos Ahmad Ittoo 《Colloid and polymer science》2008,286(2):183-190
A number of thermodynamic parameters viz. apparent molar volumes, ϕ
v
, partial molar volumes, , transfer volumes, , Falkenhagen coefficients, A, Jones–Dole coefficients, B, free energies per mole of solute, , and per mole of solvent, , molar refraction, R
D
, and limiting molar conductivity, , have been calculated by using the experimentally measured densities, ρ, viscosities, η, refractive indices, n
D
, and specific conductivities, κ, data of glycine (0.02–0.10 m) in 0.01 m aqueous sodium dodecyl sulphate, cetyltrimethylammonium bromide, and triton X-100
(TX-100) solutions at 298.15, 303.15, 308.15, and 313.15 K. The above calculated parameters were found to be sensitive towards
the interactions prevailing in the studied amino acid–surfactant–water systems. Moreover, fluorescence study using pyrene
as a photophysical probe has also been carried out, the results of which support the conclusions obtained from other techniques. 相似文献
13.
The synthesis and structural characterisation of two novel clusters, 2, and 3, are presented. They are the first examples of osmium and ruthenium clusters containing a naked
atom. 相似文献
14.
Within the Hartree-Fock framework, the spinless two-electron density function Γ (r
1, r
2) consists of direct Γdi (r
1, r
2) and exchange Γex (r
1, r
2) parts. Accordingly, the inner and outer radii in many-electron systems are rigorously separated into the direct and exchange contributions, i.e., and . It is generally shown that and , where is the usual average radius of an electron. Numerical examinations of the direct and exchange contributions for the 102 atoms
from He to Lr in their ground states find that the electron exchange works to decrease and increase . However, the exchange parts are very small and the direct parts essentially govern the inner and outer radii. 相似文献
15.
Let G be an unicycle graph and d
v
the degree of the vertex v. In this paper, we investigate the following topological indices for an unicycle graph ,
, where m ≥ 2 is an integer. All unicycle graphs with the largest values of the three topological indices are characterized.
This research is supported by the National Natural Science Foundation of China(10471037)and the Education Committee of Hunan
Province(02C210)(04B047). 相似文献
16.
Determination of norfloxacin in human urine by capillary electrophoresis with electrochemiluminescence detection 总被引:3,自引:0,他引:3
A fast and sensitive approach that can be used to detect norfloxacin in human urine using capillary electrophoresis with end-column
electrochemiluminescence (ECL) detection of is described. The separation column was a 75-μm i.d. capillary. The running buffer was 15 mmol L−1 sodium phosphate (pH 8.2). The solution in the detection cell was 50 mmol L−1 sodium phosphate (pH 8.0) and 5 mmol L−1
The ECL intensity varied linearly with norfloxacin concentration from 0.05 to 10 μmol L−1. The detection limit (S/N=3) was 0.0048 μmol L−1, and the relative standard deviations of the ECL intensity and the migration time for eleven consecutive injections of 1.0 μmol L−1 norfloxacin (n=11) were 2.6% and 0.8%, respectively. The method was successfully applied to the determination of norfloxacin spiked in human
urine without sample pretreatment. The recoveries were 92.7–97.9%.
相似文献
17.
Radosław Szmytkowski 《Journal of mathematical chemistry》2009,46(1):231-260
The derivative of the associated Legendre function of the first kind of integer degree with respect to its order, , is studied. After deriving and investigating general formulas for μ arbitrary complex, a detailed discussion of , where m is a non-negative integer, is carried out. The results are applied to obtain several explicit expressions for the associated
Legendre function of the second kind of integer degree and order, . In particular, we arrive at formulas which generalize to the case of (0 ≤ m ≤ n) the well-known Christoffel’s representation of the Legendre function of the second kind, Q
n
(z). The derivatives and , all with m > n, are also evaluated. 相似文献
18.
A concise graphical depiction, the “onion” chart, is described for presenting uncertainty budgets for any measurand, y, having a set of component variances, . The onion chart consists of a concentric series of rings. Each ring is constructed from the set of fractional contributions, . The outer ring includes all and depicts the combined standard uncertainty, u
c
(y), where u
c
2(y) ≡ ∑u
i
2(y). Moving inward, each successive ring deletes the largest remaining . A “reduced” is calculated for that ring from the remaining set of , with the fractional contributions calculated using the “reduced” . This format facilitates rapid visual comparison of the importance of each component, with minor components becoming visible as the larger components are successively deleted. An example is presented using data from pH metrology, including the physical interpretation of the resulting diagram. 相似文献
19.
Let λ1 (G) and Δ (G), respectively, denote the largest eigenvalue and the maximum degree of a graph G. Let
be the set of trees with perfect matchings on 2m vertices, and
. Among the trees in
, we characterize the tree which alone minimizes the largest eigenvalue, as well as the tree which alone maximizes the largest
eigenvalue when
. Furthermore, it is proved that, for two trees T
1 and T
2 in
(m≥ 4), if
and Δ (T
1) > Δ (T
2), then λ1 (T
1) > λ1 (T
2). 相似文献
20.
Maxim N. Sokolov Artyom L. Gushchin Dmitrii Yu. Naumov Olga A. Gerasko Vladimir P. Fedin 《Journal of Cluster Science》2005,16(3):309-318
Mechanochemical reaction of cluster coordination polymers
(Q=S, Se) with solid
leads to the cluster core excision with the formation of anionic complexes
. Extraction of the reaction mixture with water followed by crystallization gives crystalline
(main product) and
(1) (minor product). In the case of the Se cluster, the
complex could not be isolated, and the treatment of the aqueous extract with PPh3 gave
(2) in a low yield. Alternatively, it was obtained from
and
in high yield. Both 1 and 2 were characterized by X-ray structure analysis.
Dedicated to Academician I. I. Moiseev on the occasion of his 75th birthday and in recognition of his outstanding contribution
to cluster chemistry. 相似文献