共查询到20条相似文献,搜索用时 62 毫秒
1.
José ángel Rodríguez-Castrillón Mariella Moldovan J. Ignacio García Alonso 《Analytical and bioanalytical chemistry》2009,394(1):351-362
A method has been developed for the accurate determination of platinum by isotope dilution analysis, using enriched 194Pt, in environmental samples containing comparatively high levels of hafnium without any chemical separation. The method is
based on the computation of the contribution of hafnium oxide as an independent factor in the observed isotope pattern of
platinum in the spiked sample. Under these conditions, the ratio of molar fractions between natural abundance and isotopically
enriched platinum was independent of the amount of hafnium present in the sample. Additionally, mass bias was corrected by
an internal procedure in which the regression variance was minimised. This was possible as the mass bias factor for hafnium
oxide was very close to that of platinum. The final procedure required the measurement of three platinum isotope ratios (192/194,
195/194 and 196/194) to calculate the concentration of platinum in the sample. The methodology has been validated using the
reference material “BCR-723 road dust” and has been applied to different environmental matrices (road dust, air particles,
bulk wet deposition and epiphytic lichens) collected in the Aspe Valley (Pyrenees Mountains). A full uncertainty budget, using
Kragten’s spreadsheet method, showed that the total uncertainty was limited only by the uncertainty in the measured isotope
ratios and not by the uncertainties of the isotopic composition of platinum and hafnium.
Figure Simultaneous correction of hafnium oxide spectral interferences and mass bias in the determination of platinum in environmental
samples using isotope dilution analysis
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
Mariella MoldovanEmail: |
2.
Michael Thompson 《Accreditation and quality assurance》2008,13(8):479-482
The currently recommended design of collaborative trials (interlaboratory method performance studies) is examined in relation
to the usefulness of the resulting statistics. It is suggested that larger experiments, without duplicate analysis, would
be more informative.
相似文献
Michael ThompsonEmail: |
3.
René Dybkaer 《Accreditation and quality assurance》2007,12(12):661-663
Terminology within a small laboratory community can be informal without danger of misunderstanding, but communication with
a wider audience and not least in publications, needs unequivocal terms for defined concepts. As an example, the many meanings
of “concentration” are explored to present a systematic nomenclature, including a concept diagram.
相似文献
René Dybkaer |
4.
H. P. Zhang L. C. Yang L. J. Fu Q. Cao D. L. Sun Y. P. Wu R. Holze 《Journal of Solid State Electrochemistry》2009,13(10):1521-1527
Recent progress in studies of several types of core-shell structured electrode materials, including TiO2/C, Si/C, Si/SiO
x
, LiCoO2/C, and LiFePO4/C nanocomposites, including details of their preparation and their electrochemical performance is briefly reviewed. Results
clearly show that the coating shell can effectively prevent the aggregation of the nanosized cores, which are the electrochemically
active materials. In addition, the diffusion coefficients of lithium ions can be increased, and the reversibility of lithium
intercalation and deintercalation is improved. As a result, the cycling behavior is greatly improved. The reviewed results
suggest that core-shell nanocomposites are a good starting point for further development of new promising electrode materials.
相似文献
Y. P. WuEmail: |
R. Holze (Corresponding author)Email: |
5.
Hinne Hettema 《Foundations of Chemistry》2008,10(2):135-142
Michael Weisberg’s recent 2007 paper on the chemical bond makes the claim that the chemical notion of the covalent bond is
in trouble. This note casts doubts on that claim.
相似文献
Hinne HettemaEmail: |
6.
Vaporization enthalpies for the isomeric diazines were discussed within the context of recent measurements and estimation
techniques. It is suggested that pyridazine shows enigmatic behavior.
相似文献
Joel F. Liebman (Corresponding author)Email: |
7.
Sweeping and new on-line sample preconcentration techniques in capillary electrophoresis 总被引:1,自引:0,他引:1
Agnes T. Aranas Armando M. GuidoteJr. Joselito P. Quirino 《Analytical and bioanalytical chemistry》2009,394(1):175-185
Sweeping is a powerful on-line sample preconcentration technique that improves the concentration sensitivity of capillary
electrophoresis (CE). This approach is designed to focus the analyte into narrow bands within the capillary, thereby increasing
the sample volume that can be injected, without any loss of CE efficiency. It utilizes the interactions between an additive
[i.e., a pseudostationary phase (PS) or complexing agent] in the separation buffer and the sample in a matrix that is devoid
of the additive used. The accumulation occurs due to chromatographic partitioning, complexation or any interaction between
analytes and the additive through electrophoresis. The extent of the preconcentration is dependent on the strength of interaction
involved. Both charged and neutral analytes can be preconcentrated. Remarkable improvements—up to several thousandfold—in
detection sensitivity have been achieved. This suggests that sweeping is a superior and general approach to on-line sample
preconcentration in CE. The focusing mechanism of sweeping under different experimental conditions and its combination with
other on-line preconcentration techniques are discussed in this review. The recently introduced techniques of transient trapping
(tr-trapping) and analyte focusing by micelle collapse (AFMC) as well as other novel approaches to on-line sample preconcentration
are also described.
相似文献
Joselito P. QuirinoEmail: |
8.
Yan Gao Sabrina Reischmann Johannes Huber Tobias Hanke Rudolf Bratschitsch Alfred Leitenstorfer Stefan Mecking 《Colloid and polymer science》2008,286(11):1329-1334
Single semiconductor quantum dots were embedded into polymer particles with diameters below 0.1 μm by an emulsion polymerization
procedure or via a secondary dispersion approach. The photoluminescence properties of the nanocrystals are retained upon encapsulation,
as demonstrated by fluorescence confocal microscopy.
相似文献
Stefan MeckingEmail: |
9.
Guy Yardeni Israel Zilbermann Eric Maimon Haim Cohen Dan Meyerstein 《Research on Chemical Intermediates》2009,35(4):543-554
A new CeIII complex was synthesized by mixing the ligand “dioxocyclam” with CeIII ions at pH 8.0 and its redox properties were investigated.
相似文献
Dan Meyerstein (Corresponding author)Email: |
10.
11.
Micah Newman 《Foundations of Chemistry》2008,10(1):49-62
This paper surveys some ways in which the chemical realm can be described and outlined in terms of the concept of supervenience.
The particular contours of general chemical theory provide a ready basis for interpretation of determination, covariance,
and nonreduction—the characteristic metaphysical facets of the supervenience relation—in mutual terms. Building on this, the
extent to which chemically characterized properties and entities can be described in terms of a supervenience-scaffolded structure
represents a particularly vivid application that philosophers in general interested in supervenience would do well to attend
to. In addition, the model of chemical supervenience given here can be used as a rubric on which to decide on issues already
raised by philosophers of chemistry.
相似文献
Micah NewmanEmail: |
12.
Niki Baccile Anna Fischer Beatriz Julián-López David Grosso Clément Sanchez 《Journal of Sol-Gel Science and Technology》2008,47(2):119-123
Core-shell and homogeneous distributions of functionalized cerium oxide nanoparticles within spray-dried mesostructured silica
spheres are achieved by modification of synthesis parameters such as the templating agent and nanoparticle capping functions.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
Clément Sanchez (Corresponding author)Email: |
13.
A high voltage electric pulse can be applied to induce the uptake of DNA into cells and the release of protein from cells.
In transformation procedures, electroporation is widely used since the technique is simple, rapid, reproducible, and highly
efficient. In extraction of protein, on the other hand, electroextraction has many advantages over other conventional extractions.
We have developed a highly efficient method for the electroporation of fission yeast. In particular, application of a high
voltage electric pulse to fission yeast improves the cellular uptake and release of macromolecules controlled by both osmotic
conditions and electric field strength.
相似文献
Minoru SugaEmail: |
14.
Electrochemical studies of bi- and polymetallic complexes featuring acetylide based bridging ligands
Paul J. Low Rachel L. Roberts Richard L. Cordiner František Hartl 《Journal of Solid State Electrochemistry》2005,9(11):717-731
Acetylide-based bridging ligands have been widely used in the preparation of complexes that display a degree of electronic
interaction between metal-based redox groups located at the ligand termini. The electrochemical response of these systems
has been selectively reviewed, with a focus on the variation in properties that accompany changes in the structure of the
bridging ligand and the nature of the metal groups.
相似文献
Paul J. LowEmail: |
15.
S. Vatsadze M. Al-Anber W. R. Thiel H. Lang R. Holze 《Journal of Solid State Electrochemistry》2005,9(11):764-777
Reduction potentials for the first electron transfer to a broad selection of nitrogen containing bi- and polydentate molecules
considered as potential ligands have been determined. Results are compared with data obtained with semiempirical and UV-Vis
spectroscopic data. Close correlations for the investigated molecules are observed. Systematic differences in properties of
molecules with and without the keto moiety can be explained by invoking molecular orbital and surface interaction arguments.
Similar structural arguments can be used to explain the behaviour of 2,4,6-tripyridin-2–yl[1,3,5]triazine. UV-Vis data match
closely those derived from HOMO-LUMO calculations for these molecules.
相似文献
R. HolzeEmail: |
16.
The advent of chemical tools for cellular imaging—from organic dyes to green fluorescent proteins—has revolutionized the fields
of molecular biology and biochemistry. Lanthanide-based probes are a new player in this area, as the last decade has seen
the emergence of the first responsive luminescent lanthanide probes specifically intended for imaging cellular processes.
The potential of these probes is still undervalued by the scientific community. Indeed, this class of probes offers several
advantages over organic dyes and fluorescent proteins. Their very long luminescence lifetimes enable quantitative spatial
determination of the intracellular concentration of an analyte through time-gating measurements. Their emission bands are
very narrow and do not overlap, enabling the simultaneous use of multiple lanthanide probes to quantitatively detect several
analytes without cross-interference. Herein we describe the principles behind the development of this class of probes. Sensors
for a desired analyte can be designed by rationally manipulating the parameters that influence the luminescence of lanthanide
complexes. We will discuss sensors based on varying the number of inner-sphere water molecules, the distance separating the
antenna from the lanthanide ion, the energies of excited states of the antenna, and PeT switches.
相似文献
Valérie C. PierreEmail: |
17.
Saad Alshehri John Burgess Colin D. Hubbard Christopher J. Jones Amit K. Das 《Transition Metal Chemistry》2008,33(4):417-420
The kinetics of substitution by alcohols and by aniline at [tris(3,5-dimethylpyrazolyl)hydroborato]molybdenum nitrosyl dihalides in toluene solution at 298.2 K and at atmospheric pressure
are reported and interpreted in terms of an associative mechanism.
相似文献
Colin D. HubbardEmail: |
18.
Christian Schramm Beate Rinderer Wolfgang H. Binder Richard Tessadri Heinz Duelli 《Journal of Sol-Gel Science and Technology》2008,45(1):83-88
(3-Triethoxysilylpropyl)succinic anhydride (TESP-SA) is an organo-functional silicon compound that can be converted into a
polysilsesquioxane when it is hydrolyzed and subsequently subjected to a condensation reaction at elevated temperatures (>160 °C).
If this process is performed without sodium hypophosphite (SHP), a hard solid material is obtained. In contrast, the condensation
reaction of TESP-SA in conjunction with SHP results in the formation of a foamed, brittle material with closed macro cells.
The foam was characterized by means of various analytical methods (FT-IR, 29Si MAS NMR, XRD, TG-MS, SEM).
相似文献
Christian SchrammEmail: |
19.
Xavier Fuentes-Arderiu 《Accreditation and quality assurance》2006,11(12):640-643
Protometrology is a new term recently proposed to designate the science of observation. As any field of knowledge needs a
terminological system, in this article a system of terms and definitions on protometrology, with examples belonging to clinical
laboratory sciences, is presented. This terminological system starts with the definitions of the two primitive concepts “object”
and “property”.
相似文献
Xavier Fuentes-ArderiuEmail: |
20.
Michael Noyong Buelent Ceyhan Christof M. Niemeyer Ulrich Simon 《Colloid and polymer science》2006,284(11):1265-1273
The formation and the optical features of two-dimensional aggregates formed by DNA-directed immobilization and cross-linking of bifunctional DNA–gold nanoparticles at flat gold substrates are analyzed. The samples are structurally characterized by atomic force microscopy to evaluate the particle size, the particle densities, and the degree of aggregation. The optical characteristics determined by UV/visible measurements are correlated with the structural features observed.
相似文献
Ulrich SimonEmail: |