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11.
Ultraviolet (UV) spectrophotometric and nonaqueous volumetric methods are described for the determination of carvedilol in pharmaceutical formulations. Linearity, precision, and accuracy were evaluated according to the validation guidelines of the International Conference on Harmonization and the United States Pharmacopeia for both methods. The UV spectrophotometric procedure was performed in ethanol at 244 nm. Good linearity was obtained between 2 and 7 microg/mL with a correlation coefficient of 0.9999. The intra- and interday precision values were <2% for all samples analyzed. The accuracy, determined from recovery studies, was between 97.5 and 102.2%. The other procedure was based on the volumetric quantitation of carvedilol in a nonaqueous medium with 0.01 M perchloric acid and 1% violet crystal as the indicator. The validation of the volumetric method yielded good results that included linearity (r of > 0.999), precision (relative standard deviations of <2% for intra- and interday precision), and accuracy (96.4-102.4%). The methods were applied to tablets and compounded capsules. Statistical analysis by analysis of variance showed no significant difference between the results obtained by the proposed methods. 相似文献
12.
A252Cf neutron source has been used to analyse manganese in ores such as pyrolusite, rodonite (manganese silicate) and blends used in dry-batteries. Samples with about 150 mg and standards of manganese dioxide were irradiated for about 20 min and counted using a well-type NaI(Tl) scintillation counter and scaler, with or without pulse-height discriminator between the detector and the scaler. The interferences of nuclear reactions56Fe(n,p)56Mn and59Co(n,α)56Mn were studied, as well as problems in connection with neutron shadowing during irradiation, gamma-rays attenuation during counting and influence of granulometry of samples. Some of the samples were also analysed by wet-chemical method (sodium bismuthate) in order to compare results. 相似文献
13.
A flow-injection—conductimetric method was applied to the determination of ammonia, nitrate and nitrite at concentrations down to 5, 20 and 20 ng ml?1, respectively. Ammonia was determined by merging the injected sample with an alkaline solution (NaOHEDTA) and passing the mixture through a diffusion cell. The ammonia released was collected by a flowing stream of deionized water that passed through a conductance flow cell. Nitrate and nitrite concentrations were determined after reduction to ammonia in alkaline medium using a column filled with metallic zinc. The ammonia produced was then measured as described above. About 60 samples per hour can be processed with a relative standard deviation of about 1%. Satisfactory agreement was observed between results for ammonia in samples of natural water and nitrate in tap and mineral water determined by the proposed method and by standard spectrophotometric procedures. Speciation can be achieved by adding sulphanilic acid to remove nitrite from the sample and determining the ammonia without the use of the column. 相似文献
14.
Ana Luiza Coeli Cruz Ramos Laiza Andrade Nogueira Mauro Ramalho Silva Ana Carolina do Carmo Mazzinghy Ana Paula Xavier Mariano Tssia Nunes de Albuquerque Rodrigues Ana Cardoso Clemente Filha Ferreira de Paula Angelita Cristine de Melo Rodinei Augusti Raquel Linhares Bello de Araújo Inayara Cristina Alves Lacerda Júlio Onsio Ferreira Melo 《Molecules (Basel, Switzerland)》2022,27(15)
Grumixama (Eugenia brasiliensis Lam.) is a native fruit of the Brazilian Atlantic Forest, belonging to the Myrtaceae family, which designatesthe most significant number of species with food potential. It stands out due to its phytochemical characteristics because of the presence of polyphenols and volatile organic compounds. Volatile compounds are substances released by foods that give off an aroma and influence flavor. Solid-phase microextraction is a technique that allows for low-cost, fast, and solvent-free extraction, has an affinity for numerous analytes, and is easily coupled to gas chromatography. The objectives of this work were to evaluate the efficiency of different fibers of SPME (solid-phase microextraction) in the extraction of volatile organic compounds from grumixama pulp; optimize a method for extraction time, temperature, and sample weight; and to determine the characteristic volatile profile of this fruit. For the extraction of volatile compounds, three fibers of different polarities were used: polar polyacrylate (PA) fibers, divinylbenzene/carboxyne/polydimethylsiloxane (DVB/CAR/PDMS) semipolar fibers, and polydimethylsiloxane/divinylbenzene (PDMS/DVB). Fourteen volatile organic compounds (VOCs) were identified by DVB/CAR/PDMS, six by PA, and seven by PDMS/DVB through solid-phase microextraction in the headspace mode (SPME-HS). Considering the total number of compounds identified, regardless of the fiber used, and the optimization of the method, Eugenia brasiliensis presented sesquiterpene fractions (85.7%, 83.3%, and 85.7% of total VOCs) higher than the monoterpene fractions (14.3%, 16.7%, and 14.3%) for DVB/CAR/PDMS, PA, and PDMS/DVB, respectively in its composition. In addition, it was possible to verify that the fiber DVB/CAR/PDMS presented a better efficiency due to the larger chromatographic area observed when the grumixama pulp was subjected to conditions of 75 °C, 2.0 g, and an adsorption time of 20 min. 相似文献
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16.
Vitor Matos Julio D. Silva Dan Marchesin 《Bulletin of the Brazilian Mathematical Society》2016,47(2):545-559
Themain goal of ourwork is to showthat there exists a class of 2×2 Riemann problems for which the solution comprises a singlewave group for an open set of initial conditions. This wave group comprises a 1-rarefaction joined to a 2-rarefaction, not by an intermediate state, but by a doubly characteristic shock, 1-left and 2-right characteristic. In order to ensure that perturbations of initial conditions do not destroy the adjacency of the waves, local transversality between a composite curve foliation and a rarefaction curve foliation is necessary. 相似文献
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18.
As part of an ongoing program directed toward the preparation of antraciclinones1 and aryl substituted lapachones2, which are important anticancer and antibiotic3 agents, we became interested in a efficient synthesis of substituted 1,4-naphthoquinones, such as juglone (3). This compound has received some attention due its activity as an allelophatic compound4. An extensive analysis of the literature procedures indicated that several methods are available starting from 1,5-dihydroxynaphthalene (1). All the procedures explored the oxidation of carbon four of the naphthyl ring by several known reagents, such as, chromium trioxide-piridine5, thallium trinitrate5, chromic acid6, peracetic acid7, dichromate8, iron (III) chloride9 and mercuric oxide10. None of the several known methods for the preparation of (3) proceeded in satisfactory yield (except for the thallium trinitrate method which gave 642 yield) and most of them gave a mixture of 1,2 and 1,4-naphthoquinone. 相似文献
19.
Cardoso Daisy Alves Valle Eliana Maíra Agostini Codognoto Lucia 《Journal of Solid State Electrochemistry》2018,22(5):1549-1555
Journal of Solid State Electrochemistry - In this work, the interaction of the pesticide methyl parathion (MP) with the lead metal ion was evaluated using a carbon electrode reused from a zinc... 相似文献
20.
J. L. Cardoso 《Analysis Mathematica》2016,42(4):323-337
The Hahn–Exton (third Jackson) q-Bessel function attracts the attention of many researchers in mathematics. We add a few more properties of this important function, such as some identities and upper bounds involving this function, in relation with the coefficients of the corresponding basic Fourier–Bessel expansions. 相似文献