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131.
Maria Fernanda Silva Estela Soledad Cerutti Luis D. Martinez 《Mikrochimica acta》2006,155(3-4):349-364
The purpose of this article is to review and evaluate cloud point extraction of metals and its coupling to different contemporary
instrumental methods of analysis. This review covers a selection of the literature published on this topic over the period
mainly between 1997 and September 2005 (consisting of 50 publications). The current state of the art for CPE concerning metals
and metal chelates is presented with special emphasis on the hyphenation of this interesting extraction/preconcentration approach
mediated by surfactants to spectrophotometry, atomic spectroscopy and separation techniques. We present contemporary CPE developments
concerning metal speciation and determination and their application to different environmental, clinical, geological and food
samples. Strategies for method development as well as future perspectives are also covered. 相似文献
132.
Robustness experiments are performed in analytical chemistry to assess the behaviour of an analytical procedure under conditions slightly different from those of the experimental optimum. This work presents a study of robustness applied to a previously proposed fluorescent methodology using two replicated 2(7-4) saturated fractional factorial designs. A comparison is established between three different ways to test the significance of the effects of the variables involved on the response signal. Critical discussions about the most appropriate threshold to be introduced when testing for significance of the factors and the influence of the time necessary to carry out the experiments are included. 相似文献
133.
Méndez LA Jiménez J Cerrada E Mohr F Laguna M 《Journal of the American Chemical Society》2005,127(3):852-853
The symmetric digold(II)dichloride bis(ylide) complex [Au2Cl2(mu-{CH2}2PPh2)2] reacts with acetylides to form the asymmetric heterovalent gold(I)/gold(III) complexes [AuI(mu-{CH2}2PPh2)2AuIII(CCR)2] [R = Ph, tBu, and SiMe3], the phenyl analogue of which was characterized by X-ray crystallography. These compounds represent the first examples of gold(III) complexes containing two acetylide ligands. [AuI(mu-{CH2}2PPh2)2AuIII(CCPh)2] undergoes a reversible comproportionation reaction upon treatment with [Ag(ClO4)tht] to give the symmetric digold(II) cationic complex [Au2(tht)2(mu-{CH2}2PPh2)2](ClO4)2. If this complex is treated with phenylacetylene in the presence of base, the heterovalent gold(I)/gold(III) complex is re-formed. This reversible interconversion between binuclear gold(I)/gold(III) and digold(II) bis(ylide) complexes is unprecedented. 相似文献
134.
Ballesteros I. Ballesteros M. CabaÑas A. Carrasco J. MartÍn C. Negro M. J. Saez F. Saez R. 《Applied biochemistry and biotechnology》1991,(1):307-315
A total of 27 yeast strains belonging to the groupsCandida, Saccharomyces, andKluyveromyces were screened for their ability to grow and ferment glucose at temperatures ranging 32-45°C.
K. marxianus andK. fragilis were found to be the best ethanol producing organisms at the higher temperature tested and, so, were selected for subsequent
simultaneous saccharification and fermentation (SSF) studies. 相似文献
135.
María Luisa Moyá Setefilla Escalera Cristina Martín Amalia Rodríguez María Mu?oz María del Mar Graciani 《Reaction Kinetics and Catalysis Letters》2006,89(1):177-182
Summary The reaction methyl 4-nitrobenzenesulfonate + Br- was studied in water-formamide tetradecyltrimethylammonium bromide micellar solutions. A pseudophase kinetic model was used
to quantitatively rationalize the kinetic micellar effects observed 相似文献
136.
Villanueva J Villegas V Querol E Avilés FX Serrano L 《Journal of mass spectrometry : JMS》2002,37(9):974-984
In the post-genomic era, several projects focused on the massive experimental resolution of the three-dimensional structures of all the proteins of different organisms have been initiated. Simultaneously, significant progress has been made in the ab initio prediction of protein three-dimensional structure. One of the keys to the success of such a prediction is the use of local information (i.e. secondary structure). Here we describe a new limited proteolysis methodology, based on the use of unspecific exoproteases coupled with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), to map quickly secondary structure elements of a protein from both ends, the N- and C-termini. We show that the proteolytic patterns (mass spectra series) obtained can be interpreted in the light of the conformation and local stability of the analyzed proteins, a direct correlation being observed between the predicted and the experimentally derived protein secondary structure. Further, this methodology can be easily applied to check rapidly the folding state of a protein and characterize mutational effects on protein conformation and stability. Moreover, given global stability information, this methodology allows one to locate the protein regions of increased or decreased conformational stability. All of this can be done with a small fraction of the amount of protein required by most of the other methods for conformational analysis. Thus limited exoproteolysis, together with MALDI-TOF MS, can be a useful tool to achieve quickly the elucidation of protein structure and stability. 相似文献
137.
Martínez-Lozano JA Marín MJ Tena F Utrillas MP Sánchez-Muniosguren L González-Frías C Cuevas E Redondas A Lorente J de Cabo X Cachorro V Vergaz R de Frutos A Díaz JP Expósito FJ de la Morena B Vilaplana JM 《Photochemistry and photobiology》2002,76(2):181-187
An analysis is made of experimental ultraviolet erythemal solar radiation data measured during the years 2000 and 2001 by the Spanish UV-B radiation evaluation and prediction network. This network consists of 16 Robertson-Berger type pyranometers for evaluating solar erythemal radiation and five Brewer spectroradiometers for evaluating the stratospheric ozone. On the basis of these data the Ultraviolet Index (UVI) was evaluated for the measuring stations that are located either in coastal regions or in the more densely populated regions inland on the Iberian Peninsula. It has been checked that in most cases the maximum irradiance values corresponded to solar noon, although there were exceptions that could be explained by cloudiness. The maximum experimental values of the UVI were around 9 during the summer, though frequently passing this value at the inland measurement stations. The annual accumulated dose of irradiation on a horizontal plane has also been studied, as well as the evolution through the year in units of energy, standard erythemal doses and minimum erythemal doses, according to different phototypes. 相似文献
138.
The synthesis of a new epoxy resin of oligosalicylaldehyde by the reaction with epichlorohydrin is reported. New resin’s epoxy
value and chlorine content were determined and found to be 25% and 1%, respectively. The characterization of the new resin
was instrumented by FTIR, 1H NMR, scanning electron microscopy, and thermal gravimetric analyses. TGA results showed that the cured epoxy resin has a
good resistance to thermal decomposition. The mass losses of cured epoxy resin were found to be 5%, 10%, 50% at 175°C, 240°C,
and 400°C, respectively. On the curing procedure the resin was cured with polyethylenepolyamine at 25 °C for 8 h and 100°C
for 1.5 h. The FTIR spectrum of new epoxy resin gave the peak of oxirane ring at ṽ = 918 cm−1.
In memory of Professor Dr. Adalet R. Vilayetoğlu 相似文献
139.
This paper reports the development of a method based on capillary electrophoresis with laser-induced fluorescence detection for the simultaneous determination of thiouracil (TU) and phenylthiouracil (PhTU) with high sensitivity (nanomolar range, i.e., attomoles detected). After derivatization with 5-iodoacetamidofluorescein, the analytes were separated by capillary zone electrophoresis using 20 mM phosphate buffer (pH 10.0) and quantified by fluorescence detection. The linearity range, precision, recovery, and detection limits were determined, and the method was shown to be applicable for the determination of TU and PhTU in spiked feed samples and urine. 相似文献
140.
H. Dupont Durst Luis Echegoyen George W. Gokel Angel Kaifer 《Tetrahedron letters》1982,23(43):4449-4452
The 13C spin-lattice relaxation times (T1's) of cryptands [2.1.1], [2.2.1] and [2.2.2] as well as those of the corresponding cryptate complexes with Li+, Na+, and K+ in CDCl3 and CH3OH:D2O (90:10) were measured and the results are interpreted in terms of molecular compression and desolvation effects. 相似文献