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31.
The efficacy of fumed silica for removal of sorption interferences by organic surfactants in the anodic-stripping voltammetry of heavy metals is demonstrated. Appropriate addition of silica to the sample solution rapidly "purifies" it from interfering surfactants during the nitrogen purge step. Up to at least 6 ppm of gelatin, Triton X-100, albumin or Liqui-Nox then does not affect the stripping response of cadmium, lead and zinc at the hanging mercury drop electrode. A relative standard deviation of 5.5% is obtained for 20 successive measurements of 1 x 10(-7)M lead in the presence of 2 ppm Triton X-100. Analogous improvements are observed at the mercury film electrode (in the presence of up to 60 ppm of these surfactants). The use of silica thus possesses the advantages of speed, efficiency, simplicity and low cost compared to other schemes for dealing with surfactant interferences in anodic-stripping voltammetry. 相似文献
32.
The new iridium oxide film electrode, applied for the determination of lead(II), cadmium(II) and copper(II) traces using differential pulse anodic stripping voltammetry (DP ASV) is presented. The electrode display an interesting stripping voltammetric performance which compares with electrodes commonly used in voltammetry. The deposited film is known as anodically electrodeposited iridium oxide film (AEIROF). The AEIROF electrode is characterized by long‐term stability (more than 40 days) and very good reproducibility of the analytical signals in this time (≤12% for 0.5 μM of lead). The regeneration of iridium film is very simple in a time shorter than 60 seconds. The effects of various factors such as: thickness of AEIROF film, preconcentration potential and time, supporting electrolyte composition, potential interferences are optimized. The detection limit for AEIROF film electrode based on glassy carbon for an accumulation time of 30 s is as low as 7 nM for lead(II). The repeatability of the method at a concentration level of the lead(II) as low as 0.5 μM, expressed as RSD is 2.5% (n=10). The proposed method was successfully applied and validated by studying certified reference material CTA‐OTL‐1. Such an attractive use of ‘mercury–free’ ‐ environmentally friendly electrodes offers great promise to measure trace metals. 相似文献
33.
New, renewable copper (Hg(Cu)FE) and silver (Hg(Ag)FE) based amalgam film electrodes applied for the determination of elemental sulfur using differential pulse cathodic stripping voltammetry are presented. With surface areas adjustable from 1 to 12 mm2, both electrodes are characterized by very good surface reproducibility (≤2%) and long‐term stability (a few thousand measurement cycles). The mechanical refreshing of the amalgam film takes about 1–2 seconds. The effects of various factors such as instrumental parameters and the supporting electrolyte composition were optimized. Interferences from sulfides are easily removed by the addition of acid, and bubbling with argon, for Hg(Ag)FE. In the case of Hg(Cu)FE, sulfides did not interfere. The calibration graph is linear within the studied range from 16 ng L?1 to 4.8 μg L?1 for Hg(Cu)FE, and up to 6.4 μg L?1 for Hg(Ag)FE (tacc=15 s). The correlation coefficients for the two electrodes were at least 0.997. The detection limits for a low concentration of S(0) and tacc=60 s are as low as 14 ng L?1 for Hg(Cu)FE and 4 ng L?1 for Hg(Ag)FE. The proposed method was successfully applied and validated by studying the recovery of S(0) from spiked river water. 相似文献
34.
On the basis of join-continuous semigroups
, this paper demonstrates among other things that on every complete ortholattice there exists an L-valued topology such that
order convergence is L-topological (this is not always the case with respect to ordinary topologies). Further, the concept
of lower semicontinuous lattice-valued maps permits an extension of the omega-functor
to the general setting of L-valued topological spaces where the importance of
lies in the replacement of ordinary topologies by L-valued topologies. It is shown that
has a right adjoint functor iff the underlying lattice
is continuous. 相似文献
35.
36.
37.
T Fröschl U Hörmann P Kubiak G Kučerová M Pfanzelt CK Weiss RJ Behm N Hüsing U Kaiser K Landfester M Wohlfahrt-Mehrens 《Chemical Society reviews》2012,41(15):5313-5360
Titanium dioxide is one of the most intensely studied oxides due to its interesting electrochemical and photocatalytic properties and it is widely applied, for example in photocatalysis, electrochemical energy storage, in white pigments, as support in catalysis, etc. Common synthesis methods of titanium dioxide typically require a high temperature step to crystallize the amorphous material into one of the polymorphs of titania, e.g. anatase, brookite and rutile, thus resulting in larger particles and mostly non-porous materials. Only recently, low temperature solution-based protocols gave access to crystalline titania with higher degree of control over the formed polymorph and its intra- or interparticle porosity. The present work critically reviews the formation of crystalline nanoscale titania particles via solution-based approaches without thermal treatment, with special focus on the resulting polymorphs, crystal morphology, surface area, and particle dimensions. Special emphasis is given to sol-gel processes via glycolated precursor molecules as well as the miniemulsion technique. The functional properties of these materials and the differences to chemically identical, non-porous materials are illustrated using heterogeneous catalysis and electrochemical energy storage (battery materials) as example. 相似文献
38.
Nanoparticle self-assembly at fluid-fluid interfaces has been traditionally exploited in emulsification, encapsulation and oil recovery, and more recently in emerging applications including functional nanomaterials and biphasic catalysis. We provide a review of the literature focusing on the open challenges that still hamper the broader applicability of this potentially transformative technology, and we outline strategies to achieve improved control over interfacial self-assembly of nanoparticles. First, we discuss means to promote spontaneous adsorption by tuning the interfacial energies of the nanoparticles with the fluids using capping ligands, and the occurrence of energy barriers. We then examine the interactions between interfacial nanoparticles and how they affect the formation of equilibrium interfacial suspensions versus non-equilibrium two-dimensional phases, such as weakly attractive glasses and gels. Important differences with colloidal interactions in a bulk suspension arise due to the discontinuity in solvent properties at the interface. For instance, ligand brushes rearrange in asymmetric configurations, and thus play a significant role in determining interparticle interactions. Finally, we briefly discuss the link between interfacial microstructure and the dynamic response of particle-laden interfaces, including interfacial rheology and the fate of nanoparticle monolayers upon out-of-plane deformation. 相似文献
39.
Jan Janczak Ryszard Kubiak 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(1):55-57
The title antimony(III) complex, [Sb(C32H16N8)]Cl or [SbPc]Cl (where Pc = C32H16N82−), has been obtained from the reaction of pure powdered antimony with 1,2-dicyanobenzene under a stream of ICl vapour. The asymmetric unit of this complex consists of an [SbPc]+ cation and a Cl− anion. The phthalocyaninate residue [SbPc]+ is not planar. The Sb atom lies 1.057 (3) Å from the plane defined by the four isoindole N atoms. A combination of ionic and donor–acceptor interactions links the [SbPc]Cl molecules to form centrosymmetric [(SbPc)Cl]2 pseudo-dimers in the crystal. The Sb—Cl distances in the pseudo-dimer are not equivalent [3.043 (2) and 3.201 (2) Å]. The pseudo-dimers are weakly linked through Cl⃛H—Cbenzo interactions to form a three-dimensional network. As a result of these interactions, the four Sn—Nisoindole bond lengths in the [SbPc]+ residue are not equivalent and the symmetry of the Sb—N core is only close to Cs. 相似文献
40.
R. Kubiak T. Muller T. Maurer K. W. Eichhorn 《International journal of environmental analytical chemistry》2013,93(1-4):349-358
Abstract Comparative volatilization experiments were carried out using isoproturon and parathion-methyl sprayed on French beans in field experiments and on plant stands (0.5 m2) in the volatilization chamber developed by the SLFA Neustadt using both compounds 14C-labelled. The experimental conditions in the field experiments concerning wind speed, temperature and humidity fluctuations were simulated in the volatilization chamber. The laboratory experiment reflected the actual outdoor situation, showing only a negligible amount of volatile isoproturon directly measured in air samples, and providing no reduction of the A.I. residues in plants compared with the initial value in the corresponding field experiment. 77.2% of the parathion-methyl applied to the plants were volatilized and measured directly in air samples in the volatilization chamber while a reduction by 74.7% was found for the corresponding field experiment by residue analysis of the plants after 24 h. No details could be given concerning the nature of the evaporated portions in the field experiment. 相似文献