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101.
A selective method based on high performance liquid chromatography with electrochemical detection (HPLC-ECD) was developed to enable simultaneous detection of 8-oxo-7,8-dihydroguanine (8-oxoGua) and 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodGuo), products of DNA oxidative damage, in the presence of uric acid (UA), a strong interferent in their electrochemical detection. The method developed consists of HPLC isocratic elution with amperometric detection on a glassy carbon electrode, enabling a detection limit for 8-oxoGua and 8-oxodGuo lower than 1 nM in standard mixtures. Detection of low concentrations up to 25 nM of 8-oxoGua and 8-oxodGuo in the presence of UA in a 104-fold higher concentration was achieved after one-step solid phase extraction (SPE). The method was tested with urine samples and it was possible to detect and quantify the presence of 8-oxoGua, and to confirm that UA was eliminated after uricase degradation and SPE. The LOD found in urine samples was about 80 nM, a value higher than in standard mixtures, due to the increase of background current in the urine matrix. The results presented here contribute to the development of a methodological approach to simultaneous determination of 8-oxoGua and 8-oxodGuo in urine samples. 相似文献
102.
Ana Montero 《Tetrahedron letters》2005,46(3):401-405
A stereocontrolled synthesis of an unsaturated sugar bearing two amino groups (one of them masked as an azide), using an Overman rearrangement as key step, is described. This scaffold is used to prepare two peptides having aromatic fragments, which have shown activity as calpain inhibitors. 相似文献
103.
Ricardo H. M. Godoi Ana F. L. Godoi Anna Worobiec Sandro J. Andrade Johan de Hoog Mary R. Santiago-Silva Rene Van Grieken 《Mikrochimica acta》2004,145(1-4):53-56
Biomass burning is an important primary and secondary source of aerosol particles. The presence of carbonaceous particles in the respirable size range makes the study of this fraction important in view of possible health and climatic effects. The annual burning of sugar cane plantations causes emission of huge amounts of pyrogenic particles. Aerosol samples were collected in Araraquara city, São Paulo state, Brazil, during the harvest season for fine and coarse particles and bulk; they were analysed by electron-probe microanalysis, including facilities for low-Z element determination (low-Z EPMA) and by energy-dispersive X-ray fluorescence (EDXRF), in order to investigate the elemental composition of individual particles and bulk samples, respectively. Numerical analysis of the EPMA results by hierarchical clustering shows high contributions of carbonaceous particles that can be distinguished mainly in two different types: biogenic and carbon-rich. Additionally, two significant contributions of aluminosilicate particles were identified: as rather pure aluminosilicates or mixed with carbonaceous species. The EDXRF results are compatible with those of aerosol particles in Amazon, which is nowadays one of the main sources of biogenic particles in the world. 相似文献
104.
Jaime González Velasco 《Central European Journal of Chemistry》2005,3(3):470-481
The analytical treatment of a model considering the electrooxidation of p-porous silicon layers under galvanostatic conditions
is able to give account of experimental facts such as the shape and location of the electroluminescence peak as well as of
the spectral shift of the electroluminescence peak produced by oxidation. The proposed model considers electroluminescence
to be the result of electron injection into the conduction band by an adsorbed intermediate produced by electrooxidation of
the surface coverage with hydrogen or siloxene of the silicon nanocrystallites. The access of holes to the surface is made
possible by low accumulation layer conditions and is the rate determining step in the electroluminescence mechanism. In this
way it is possible to give a satisfactory explanation to the shift towards the blue experimented by the electroluminiscence
emission maximum as a consequence of electrooxidation. 相似文献
105.
C. F. Gonzàlez-Fernandez M. Espinosa-Jimènez F. Gonzàlez-Caballero 《Colloid and polymer science》1983,261(8):688-693
An experimental investigation on streaming potentials of porous plugs of cellulose in both the linear and the non-linear range is described. The variation of the electrokinetic coefficients as a function of fibre concentration in the porous pad has been studied, using solutions of different concentration of Congo Red dye as a permeant. The trend observed for changes of both linear electrokinetic coefficientL 21 and non-linear coefficientL 211 as packing density,c F, increases, is somewhat analogous, the similarity suggesting some proportionality between both coefficients. The electroviscous effect accounts for the decrease ofL 211 with the increase ofc F. The coefficientL 221 was found to be always negative and, in absolute value, to decrease with increasingc F. Second-order coefficients have been interpreted in terms of modifications of “generalized conductivities” produced by the changes of thermodynamic forces. 相似文献
106.
α-(1-adamantyl)-β-diketones are now accessible by the alkylation of Co(II) complexes of β-diketones with 1-bromoadamantane. The intermediacy of adamantyl cation is proposed. Co(II), Co(III) and Zn(II) complexes of pentane-2,4-dione react with alkyl halides precursors of stabilized carbenium ions, to give 3-alkylpentane-2,4-diones. 相似文献
107.
A solution of a Zn-complex of recombinant mouse MT-1 isoform (Zn(7)-MT-1) was prepared and titrated with Cd(2+) ions. A method based on the coupling of capillary zone electrophoresis (CZE) with electrospray MS detection was developed for the analysis of the stoichiometry of the species formed during the titration. The method offered the possibility of the on-line removal of up to 100 mM Tris or phosphate buffer solutions that would otherwise suppress the electrospray signal. By allowing the determination of the metal stoichiometry of the complex species present in solution the method was shown to be complementary to circular dichroism and UV-VIS spectrophotometry conventionally used for similar studies. The titration of the Zn(7)-MT complex with Cd(II) showed the sequential displacement of the Zn by Cd. The unusually high stability of the Cd(6)Zn(1)-MT species was observed which suggests a structural role of the remaining Zn(II) ion. 相似文献
108.
Determination of triclosan in foodstuffs 总被引:1,自引:0,他引:1
Sanches-Silva A Sendón-García R López-Hernández J Paseiro-Losada P 《Journal of separation science》2005,28(1):65-72
A reverse-phase high-performance liquid chromatographic (RP-HPLC) method coupled with an ultraviolet detector was developed to determine triclosan which had migrated into foodstuffs from packaging materials. The method includes extraction with hexane, followed by evaporation to dryness and residue re-dissolution in ACN 90%. Chromatographic separation was performed with a Kromasil 100 C18 column (15 cm x 0.4 cm ID, 5 microm particle size) at 30 degrees C and using ACN and water as mobile phases. Regarding recoveries, good results (higher than 83% and lower than 112%) were obtained for the three representative food matrixes selected (orange juice, chicken breast meat, and Gouda cheese). 相似文献
109.
Baeyer-Villiger oxidation with potassium peroxomonosulfate supported on acidic silica gel 总被引:1,自引:0,他引:1
González-Núñez ME Mello R Olmos A Asensio G 《The Journal of organic chemistry》2005,70(26):10879-10882
[reaction: see text] Potassium peroxomonosulfate deposited onto silica SiO2 x KHSO5 efficiently reacts with ketones in dichloromethane at room temperature to give the corresponding esters or lactones in quantitative yields. This method avoids hydrolysis of the reaction products. The Baeyer-Villiger reaction is catalyzed by potassium hydrogensulfate present in the supported reagent. 相似文献
110.
Comas E Gimeno RA Ferré J Marcé RM Borrull F Rius FX 《Journal of chromatography. A》2003,988(2):277-284
We used the Generalized Rank Annihilation Method (GRAM), a second-order calibration method, to quantify aromatic sulfonates in water with high-performance liquid chromatography (HPLC) when interferences coeluted with the analytes of interest. With GRAM, we can quantify in only two chromatographic analyses, one for a calibration sample and one for the unknown sample. The calculated concentrations were not statistically different to those obtained when the chromatographic separation of the unknown sample was modified in order to completely separate the analyte from the interferences before univariate calibration. With GRAM, the concentrations are determined much more quickly because a complete resolution is not required. 相似文献