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31.
Aurora González-Portal F. Bermejo-Martínez C. Baluja-Santos María Cristina Diez-Rodríguez 《Microchemical Journal》1985,31(3):368-374
A new method for the Spectrophotometric determination of bismuth using N-(2-acetamido)iminodiacetic acid as complexometric agent is proposed. The complex is formed in a wide pH range, 5.5–7.5, and has a maximum absorption at 265 nm. Beer's law is obeyed in the interval 3.8–17.9 μg of bismuth(III)/ml, with a minimum photometric error of 2.3. The molar absorptivity is 9.1 × 103 liters/cm mol. The stoichiometry of the reaction takes place in the metal-to-ligand ratio 1:2. The interferences produced by the more common ions are studied. The method has been successfully applied to the determination of bismuth in pharmaceutical formulations. 相似文献
32.
Iodine-poly(2-vinylpyridine-co-styrene-co-divinylbenzene) charge transfer complexes with antibacterial activity 总被引:1,自引:0,他引:1
Angela Cristina Jandrey Mônica Regina Marques Palermo de Aguiar José Luiz Mazzei 《European Polymer Journal》2007,43(11):4712-4718
In this work, we have developed three different copolymers based on 2-vinylpyridine, styrene and crosslinked with divinylbenzene (10-30 mol%). The copolymers were morphologically and chemically characterized by apparent density, swelling degree, elemental analysis, Fourier transform infrared spectrophotometry and optical microscopy. The formation of iodine complexes with these copolymers was carried out by two different procedures: with solvent, or not. The influence of the copolymers structure on the capacity of anchoring iodine has been investigated. The antibacterial properties of polymeric charge transfer complexes were determined towards 103-107 cells/mL dilutions from the auxotrophic AB1157 Escherichia coli strain. 相似文献
33.
[reaction: see text] The phosphoramidite 11 was prepared in three steps from methyl 2-mercaptoacetate and demonstrated efficiency in the synthesis of conventional 5'-/3'-phosphate/thiophosphate monoester derivatives of 2'-deoxyribonucleosides and DNA oligonucleotides. Moreover, the use of 11 has enabled the preparation of the dinucleoside phosphorothioate analogue 26 in high yields (>95%) with minimal cleavage (<2%) of the thermolytic thiophosphate protecting group. 相似文献
34.
We have upgraded a Self-consistent-field – Hartree–Fock routine to include a finite nuclear mass correction for molecules developed in our laboratory. The new routine can handle isotopomers without calculating any nuclear kinetic energy matrix element. Tests on H2, LiH, HF, F2, and H2O isotopomers indicate the equivalence of our correction to the standard diagonal adiabatic correction. A further original application to C2H6 illustrates the usefulness of the method for polyatomic molecules. The resulting molecular orbitals carry the nuclear mass signature, exemplified with Koopmans ionization potentials.From the Proceedings of the 28th Congreso de Químicos Teóricos de Expresión Latina (QUITEL 2002) 相似文献
35.
A set of amino-group possessing cyanine dyes is obtained from their N-acetyl derivatives via deprotection with boron trifluoride-methanol complex in good yields. 相似文献
36.
Capozzi G Delogu G Fabbri D Marini M Menichetti S Nativi C 《The Journal of organic chemistry》2002,67(7):2019-2026
Sulfenylation of 6,6'-dimethoxy-2,2'-dihydroxybiphenyl, used as a racemic mixture and single enantiomers, by phthalimidesulfenyl chloride afforded the corresponding 3,3'-N,N'-dithiophthalimide with complete regioselectivity. Simple manipulations of the latter compound allowed access to the corresponding bis-thiol or o-thioquinone as useful intermediates for the synthesis of new sulfur-containing open-chain and macrocyclic C(2) enantiopure ligands. The application of this methodology to the preparation of a biphenyl bearing two cysteine units as potential HIV-1 protease inhibitor is also described. 相似文献
37.
M. C. Freitas M. M. Farinha A. M. G. Pacheco M. G. Ventura S. M. Almeida M. A. Reis 《Journal of Radioanalytical and Nuclear Chemistry》2005,263(3):710-720
Summary Selenium is determined by instrumental neutron activation analysis (INAA), based on measurement of the long-lived 75Se nuclide. In the urban and industrialized areas of Portugal selenium contents have been found of the order of of 0.5-1 ng/m3 in PM10 and PM2.5, according to the data collected since 1994. From November 12, 2001 and for not more than 3 months, the Se contents in PM10 and PM2.5 increased by a factor of 1000 in the northern area of Lisbon. More than other nutrients, selenium illustrates the dichotomy between essentiality and toxicity. There is no legislation on Se for ambient air and on indoor ambient point threshold limit values (US and Germany legislation), were 100 times higher than the abnormal values found that winter. The increase was also visible for mercury although not to such an extent. Attempts were made to understand the trend, going into a study of the emission sources located in the area using both INAA and PIXE. It was concluded that the observation occurred due to abnormal meteorological wind direction, which pushed the pollutants towards the populated area, when usually they flow into the Tagus estuary. 相似文献
38.
Single-site heterogeneous Cr-based catalyst for the selective trimerisation of ethylene 总被引:1,自引:0,他引:1
TAC-Cr3+/SiO2 complexes are highly active and selective ethylene trimerisation catalysts and possess single-site catalytic behaviour, an unusual property for heterogeneous catalysts. 相似文献
39.
Optimisation of stir bar sorptive extraction for the analysis of volatile phenols in wines 总被引:2,自引:0,他引:2
An easy, fast and reliable analytical method is proposed for the determination of the concentration of volatile phenols (ethyl- and vinylphenols) in wines. The novel stir bar sorptive extraction (SBSE) technique is employed, following a simple and fast procedure that allows 15 samples to be extracted simultaneously using very small sample volume. Extracts are desorbed in a thermodesorption system (TDS) coupled on-line to a gas chromatograph-mass spectrometry system. The SBSE offers better recovery and linear regression coefficient (r2) for the four volatile phenols than solid-phase extraction (SPE). The mass spectrometric detection in selected ion monitoring mode contributes to the lower detection limit and good sensibility obtained with this method. 相似文献
40.
Marengo E Liparota MC Robotti E Bobba M Gennaro MC 《Analytical and bioanalytical chemistry》2005,381(4):884-895
A new method has been developed for monitoring the degradation of paintings. Two inorganic pigments (ultramarine blue and red ochre) were blended with linseed oil and spread on canvas. Each canvas was subjected to simulated accelerated ageing in the presence of typical degradation agents (UV radiation and acidic solution). Periodically the painted surfaces were analysed by FT-Raman, to investigate the status of the surface. The data obtained were analysed by principal component analysis (PCA). Finally the Shewhart and cumulative sum control charts based on the relevant principal components (PC) and the so called scores monitoring and residuals tracking (SMART) charts were built. The method based on the use of PC to describe the process was found to enable identification of the presence of relevant modification occurring on the surface of the samples studied.Electronic supplementary material Supplementary material is available for this article at 相似文献