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排序方式: 共有122条查询结果,搜索用时 15 毫秒
11.
M Llobat-Estellés A R Maurí-Aucejo M D López-Catalán 《Fresenius' Journal of Analytical Chemistry》2001,371(3):358-363
A method has been developed for the determination of chromium in presence of V(V), Mo(VI), and Fe(III). The effects of interferences were evaluated by using the apparent content curves method, and their separation was performed by solid-phase extraction with an anionic exchanger. The sample-treatment conditions and the influence of the sample conductivity were studied. Tolerance limits were established, and the proposed procedure was used to determine chromium in certified samples and for speciation of chromium in waste water. Our results were always in agreement with the theoretical content. 相似文献
12.
Maurício Hilgemann Fritz Scholz Heike Kahlert Leandro Machado de Carvalho Marcelo Barcellos da Rosa Ulrike Lindequist Martina Wurster Paulo C. do Nascimento Denise Bohrer 《Electroanalysis》2010,22(4):406-412
A new electrochemical assay has been developed which is based on quantifying the attack of OH. radicals on a self‐assembled thiol monolayer on electrodes in the presence and absence of antioxidants. The OH. radicals were produced in Fenton solutions. The radical scavengers diminish the concentration of the OH. radicals in the Fenton solution, and the extent of thiol layer destruction is monitored with the help of a redox probe in solution, the signal of which is only generated at SAM‐free electrode surface. The results of the electrochemical assay were compared with those of the standard DPPH. assay. In case of each plant extract, an excellent linear correlation was observed between the radical scavenging activity and the concentration of plant extracts; however, the scavenging properties of different plants strongly differ in the electrochemical and the DPPH. assay. Since the proposed new method probes the reactivity of radical scavengers towards OH., one of the most important reactive oxygen radicals in tissues, it is supposed to provide much more relevant information than the DPPH. or other assays. 相似文献
13.
InGaN/GaN nanorod core-shell LEDs have shown to be very promising candidates for high efficiency lighting devices. Such nanorods can be grown in different ways, leading to different device geometry and in particular to different structures near the polar Ga- and N-face nanorod surfaces. In this work the influence of the properties of the polar surfaces on the electrical device behaviour is studied qualitatively based on a semiclassical simulation model. 相似文献
14.
Jos�� Fl��vio Marcelino Borges Marlon Luiz Hneda Andr�� Maur��cio Brinatti Jo?o Batista Marimon da Cunha Jadir Aparecido Rosa Jos�� Domingos Fabris 《Hyperfine Interactions》2011,203(1-3):9-15
A sample of the coarse sand fraction from the soil material of the A-horizon (0?C0.2 m from the soil surface) of a dusky red magnetic Oxisol was submitted to high-energy mechanical milling for different times. This assay aimed mainly at (a) monitoring the individualization of strongly aggregated mineral particles, and (b) measuring the effect of the milling pressure on the mineralogy changes of the material. These data are also intended to experimentally subside any physical model describing the mechanical behavior of the superficial soil layer that is subjected to intensive machine management, in agriculture fields. Powder X-ray data reveal that some mineralogical phases, notably gibbsite, disappear soon after the first few hours milling. The 298 K-transmission Mössbauer spectrum for the non-milled sand sample shows a qualitatively typical pattern for the sand fraction of basalt derived soils, with magnetically ordered sextets, assignable mainly to hematite and maghemite, and an intense central (super)paramagnetic Fe3?+? doublet. For the milled samples, spectra revealed progressive spectral reduction of the magnetic hyperfine structure, with concomitant increase of relative subspectral areas due to (super)paramagnetic phases, as the milling time increased. This result is consistent with the reduction of measured saturation magnetization, from 4.96(8) J T???1 kg???1, for the non-milled sample, to 3.26(7) J T???1 kg???1, for the sample milled for 8 hours. 相似文献
15.
A. Cerdán-Vidal A. R. Maurí-Aucejo M. Llobat-Estellés M. C. Pascual-Martí 《Analytical and bioanalytical chemistry》1997,357(6):572-576
The Intersection Point Method (IPM) is a new method for the determination of an analyte in the presence of several unknown
interferences. The method is based on the Apparent Content Curves (ACC) from derivative signals. To test the proposed procedure
an analysis of mixtures of indicators with strong spectral overlapping was carried out. Results obtained agree with the theoretical
values. Besides, the determination of caffeine in several pharmaceuticals by IPM provides good results.
Received: 11 April 1996 / Revised: 10 June 1996 / Accepted: 14 June 1996 相似文献
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A. Cerdán-Vidal A. R. Maurí-Aucejo M. Llobat-Estellés M. C. Pascual-Martí 《Fresenius' Journal of Analytical Chemistry》1997,357(6):572-576
The Intersection Point Method (IPM) is a new method for the determination of an analyte in the presence of several unknown
interferences. The method is based on the Apparent Content Curves (ACC) from derivative signals. To test the proposed procedure
an analysis of mixtures of indicators with strong spectral overlapping was carried out. Results obtained agree with the theoretical
values. Besides, the determination of caffeine in several pharmaceuticals by IPM provides good results.
Received: 11 April 1996 / Revised: 10 June 1996 / Accepted: 14 June 1996 相似文献
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Carla Maria Mariano Fernandez Maurício Ferreira da Rosa Ana Claudia Aparecida Mariano Fernandez Wanessa de Campos Bortolucci Fabiana Borges Padilha Ferreira Giani Andrea Linde 《Natural product research》2020,34(5):731-735
AbstractThis study, was to evaluate the acaricidal effect of the essential oil (EO) and fractions (FR) obtained from Laurus nobilis leaves on Rhipicephalus (Boophilus) microplus. Eight fractions were obtained, however FR1: sabinene (37.83%), β-pinene (13.50%), 1,8-cineole (12.66%), α-pinene (12.56%) and FR8: α-terpineol (79.19%) were highlighted as to the larvicidal potential when submitted by Larval Packet Test. The EO was tested by the Adult Immersion Test, at concentrations of 200.00; 100.00 and 50.00?µL/mL caused mortality of engorged females, egg mass reduction and hatching inhibition. Two fractions are shown to be efficient in controlling larvae FR8 (LC50?=?0.13?µL/mL, LC99?=?0.51?µL/mL) and FR1 (LC50?=?0.20?µL/mL, LC99?=?0.56?µL/mL). The fractionation of EO was determinant to elucidate which compounds were responsible for the larvicidal potential. This study opens new perspectives to direct new bioassays with the compounds obtained in the fractionation, since they present high potential on cattle tick larvae. 相似文献