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91.
Because of the widespread use, increased application of new formulations and immense impact on organisms and ecology surfactants
are still in the focus of analytical chemistry. The development of methods with higher selectivity and lower detection limits
is important to meet the requirements of greater responsibility for health of people and environment. Efficient separation
methods, like HPLC, GC and CE, in combination with sensitive detection, like MS, are to be preferred over collective techniques
which can suffer from interfering components. A review on trace analysis of ionic and neutral surfactants including sample
preparation steps is presented, considering especially those methods which provide information about homologous and isomeric
distribution of surfactant mixtures. Examples for the determination of linear alkylbenzene sulfonates in river water by HPLC
and CE are discussed to show the capability of these methods for environmental analyses. As future trends increased applications
of LC/MS (very high sensitivity) and also of CE (robustness and possibility for rapid method development) can be predicted.
Received: 30 July 1998 / Revised: 28 October 1998 / Accetped: 1 November 1998 相似文献
92.
93.
Jrn Piel Jens Donath Katja Bandemer Wilhelm Boland 《Angewandte Chemie (International ed. in English)》1998,37(18):2478-2481
Terpenoids from flower and leaf volatiles are predominantly synthesized along the mevalonate-independent pathway, as shown by administration of [D2]deoxy-D -xylulose and [D5]mevalolactone. The parallel use of two pathways for the biosynthesis of the sesquiterpenoid-derived 4,8-dimethylnona-1,3,7-triene (DMNT, see picture) may be important to ensure the synthesis of the volatile alarm codes of plants. 相似文献
94.
Katja Jankova Jrgen Kops Xianyi Chen Walther Batsberg 《Macromolecular rapid communications》1999,20(4):219-223
Diblock copolymers of poly(ethylene‐co‐butylene) and polystyrene or poly(4‐acetoxystyrene) are synthesized by atom transfer radical polymerization (ATRP) using a 2‐bromopropionic ester macroinitiator prepared from commercial monohydroxyl functional narrow dispersity hydrogenated polybutadiene (Kraton Liquid Polymer, L‐1203). ATRP carried out in bulk and in xylene solution with cuprous bromide and two different complexing agents 2,2′‐bipyridine (bipy) and 1,1,4,7,10,10‐hexamethyltriethylenetetraamine (HMTETA) yielded well‐defined diblock copolymers with polydispersities around 1,3. The diblock copolymer with poly(4‐acetoxystyrene) was hydrolyzed to the corresponding poly(4‐hydroxystyrene) sequence. 相似文献
95.
Sohrab Kheradmandan Katja Heinze Helmut W. Schmalle Heinz Berke 《Angewandte Chemie (International ed. in English)》1999,38(15):2270-2273
Building blocks for conducting polymers or NLO materials are the linear, unsaturated carbon chain bridged manganese complexes 1 n+ (n=0–2). All oxidation states were investigated spectroscopically and by X-ray structure determinations. The analytical data confirm a communication of the electrons over the C4 chain—a prerequisite for electrical conductivity and NLO properties of oligo- or polymeric materials. 相似文献
96.
Vladimir A. Sivakov Dr. Katja Höflich Michael Becker Dr. Andreas Berger Dr. Thomas Stelzner Dr. Kai‐Erik Elers Dr. Viljami Pore Dr. Mikko Ritala Prof. Dr. Silke H. Christiansen Dr. 《Chemphyschem》2010,11(9):1995-2000
A new method to prepare plasmonically active noble metal nanostructures on large surface area silicon nanowires (SiNWs) mediated by atomic layer deposition (ALD) technology has successfully been demonstrated for applications of surface‐enhanced Raman spectroscopy (SERS)‐based sensing. As host material for the plasmonically active nanostructures we use dense single‐crystalline SiNWs with diameters of less than 100 nm as obtained by a wet chemical etching method based on silver nitrate and hydrofluoric acid solutions. The SERS active metal nanoparticles/islands are made from silver (Ag) shells as deposited by autometallography on the core nanoislands made from platinum (Pt) that can easily be deposited by ALD in the form of nanoislands covering the SiNW surfaces in a controlled way. The density of the plasmonically inactive Pt islands as well as the thickness of noble metal Ag shell are two key factors determining the magnitude of the SERS signal enhancement and sensitivity of detection. The optimized Ag coated Pt islands on SiNWs exhibit great potential for ultrasensitive molecular sensing in terms of high SERS signal enhancement ability, good stability and reproducibility. The plasmonic activity of the core‐shell Pt//Ag system that will be experimentally realized in this paper as an example was demonstrated in numerical finite element simulations as well as experimentally in Raman measurements of SERS activity of a highly diluted model dye molecule. The morphology and structure of the core‐shell Pt//Ag nanoparticles on SiNW surfaces were investigated by scanning‐ and transmission electron microscopy. Optimized core–shell nanoparticle geometries for maximum Raman signal enhancement is discussed essentially based on the finite element modeling. 相似文献
97.
Nonlinear systems with stochastic parameters are approximated by simpler systems using a method that we call statistical replacement. This method is an extension of the previously developed AGREE which was restricted to systems with additive fluctuations. Statistical replacement incorporates the distinctions between globally stable thermodynamically closed systems and thermodynamically open systems that can be unstable. 相似文献
98.
This paper deals with the use of Cu(II) complexes of L-tartaric acid or L-threonine as selectors for the chiral separation of drugs containing amino alcohol structure by ligand-exchange CE. Using Cu(II) ions as a complexing agent, a series of sympathomimetics and beta-blockers were resolved. It was found that the resolution strongly depends on selector concentration and pH. The optimum pH for complexation was 12. 相似文献
99.
Bond AD García F Jantos K Lawson GT McPartlin M Wright DS 《Chemical communications (Cambridge, England)》2002,(12):1276-1277
The novel, deca-lithium cage [(mtaNHLi)(As2(Nmta)5)-Li(4).2thf]2 (1) (mtaN = 5-methylthiazolyl, C4H4N2S) contains an imido-bridged tetraanion [(mtaN)2As(mu-Nmta)-As(Nmta)2]4-, which represents a new type of multi-functional imido group 15 ligand framework (homologous with group 15 anions of the type [As(NR)3]3-). 相似文献
100.
Katja Heinze Prof. Dr. Klaus Hempel Dipl.‐Chem. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(6):1346-1358
The synthesis of two series of peptidic chains composed of bis(terpyridine)ruthenium(II) acceptor units and organic chromophores (coumarin, naphthalene, anthracene, fluorene) by stepwise solid‐phase peptide synthesis (SPPS) techniques is described. The first series of dyads comprises directly amide linked chromophores, while the second one possesses a glycine spacer between the two chromophores. All dyads were studied by UV/Vis and NMR spectroscopy, steady‐state luminescence, luminescence decay and electrochemistry, as well as by DFT calculations. The results of these studies indicate weak electronic coupling of the chromophores in the ground state. Absorpion spectra of all dyads are dominated by metal‐to‐ligand charge‐transfer (MLCT) bands around 500 nm. The bichromophoric systems, especially with coumarin as organic chromophore, display additional strong absorptions in the visible spectral region. All complexes are luminescent at room temperature (3MLCT). Efficient quenching of the fluorescence of the organic chromophore by the attached ruthenium complex is observed in all dyads. Excitation spectra indicate energy transfer from the organic dye to the ruthenium chromophore. 相似文献