Experiments In Chemistry
Mostrando 25-36 de 150 artigos, teses e dissertações.
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25. Evaluation of Direct Analysis for Trace Elements in Tea and Herbal Beverages by ICP-MS
In general, inductively coupled plasma mass spectrometry (ICP-MS) food analysis requires numerous sample treatment steps that imply an increase of analysis time and the use of chemicals. In this study, the main objective was to evaluate the applicability of the direct analysis by ICP-MS to determine twelve elements (Al, As, Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Se
J. Braz. Chem. Soc.. Publicado em: 2015-06
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26. Collision-Induced Dissociation Analysis of Brevianamide A and C in Electrospray Ionization Mass Spectrometry
Brevianamides A and C are isomeric cyclic peptides with several reported biological activities, isolated from diverse microorganisms. Currently, there has been no previous investigation of brevianamide fragmentation utilizing electrospray ionization mass spectrometry (ESI-MS). In this work experiments were carried out in the positive mode using two different
J. Braz. Chem. Soc.. Publicado em: 2015-04
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27. QUÍMICA VERDADEIRAMENTE VERDE – PROPRIEDADES QUÍMICAS DO CLORO E SUA ILUSTRAÇÃO POR EXPERIMENTOS EM ESCALA MINIATURIZADA
Chlorine, one of the most frequent elements on earth and most important key chemicals, is indispensable in the syllabi of school and university courses in Inorganic Chemistry. However, its toxicity and high volatility preclude experimental demonstration of its properties in secondary and high schools and most university labs. This paper summarises the indust
Quím. Nova. Publicado em: 2015-03
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28. ENZYMATIC RESOLUTION OF ANTIDEPRESSANT DRUG PRECURSORS IN AN UNDERGRADUATE LABORATORY
The use of biocatalysts in synthetic chemistry is a conventional methodology for preparing enantiomerically enriched compounds. Despite this fact, the number of experiments in chemical teaching laboratories that demonstrate the potential of enzymes in synthetic organic chemistry is limited. We describe a laboratory experiment in which students synthesized a
Quím. Nova. Publicado em: 2015-02
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29. Resgatando um método eficiente para determinação do ponto de ebulição de substâncias orgânicas: percolador versus Siwoloboff
The aim of this paper was to revive the accurate determination of the boiling point of organic compounds using the percolator technique developed in the 1960s. Although this method is simple, fast and efficient it is omitted from current textbooks. This method has several advantages over Siwoloboff such as high reproducibility and direct measurement of the b
Quím. Nova. Publicado em: 2014-06
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30. Detection and identification of huwentoxin-IV interacting proteins by biotin-avidin chemistry combined with mass spectrometry
Background : Numerous spider toxins are of interest as tools for neurophysiological research or as lead molecules for the development of pharmaceuticals and insecticides. Direct detection and identification of the interacting proteins of a spider toxin are helpful for its action-mechanism analysis and practical application. The present study employed a com
J. Venom. Anim. Toxins incl. Trop. Dis. Publicado em: 20/05/2014
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31. Síntese de cristais líquidos derivados do nitroazobenzeno: uma proposta de síntese multi-etapas aplicada às aulas de química orgânica experimental
We describe a synthetic route consisting of five steps from aniline to obtain liquid crystal compounds derived from nitroazobenzene. Syntheses were performed during the second half of the semester in organic chemistry laboratory classes. Students characterized the liquid crystal phase by the standard melting point techniques, differential scanning calorimetr
Quím. Nova. Publicado em: 2014
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32. Preparação de derivados do lapachol em meio ácido e em meio básico: uma proposta de experimentos para a disciplina de Química Orgânica Experimental
In this educational paper we describe the extraction of lapachol from its natural source according to acid-base concepts in organic chemistry and the use of its derivatives β-lapachone and hydroxy-hydrolapachol to exemplify intramolecular cyclization, carbocation stability, Michael addition reaction and chromatography. The experiments were performed during
Quím. Nova. Publicado em: 2013
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33. Acoplamento de cloreto de 4-nitrofenildiazônio com nucleófilos alifáticos: experimento integrado de síntese orgânica e cristalografia de raios X
This article describes an undergraduate experiment for the synthesis of p-nitrophenyldiazonium chloride and its coupling with acetylacetone and two enaminones, 4-phenylamino-pent-3-en-2-one and 4-amino-pent-3-en-2-one, in an adaptation of a previously reported synthetic protocol. The azo dyes 4-(E)-phenylamino-3-[(E)-2-(4-nitrophenylazo)]-3-penten-2-one and
Quím. Nova. Publicado em: 2013
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34. Desenvolvimento do Software PlanEx de planejamento de experimentos online e sua aplicação didática na pós-Graduação / PlanEx a Web/Online Software for Design of Experiments: Development, and Evaluation in Graduate Chemistry Course
Esta Tese apresenta o software PlanEx que contém as ferramentas do planejamento de experimentos fatorial escritas em linguagem de programação Java. O objetivo do trabalho foi desenvolver o software PlanEx e validá-lo como uma ferramenta de ensino e pesquisa simples, eficiente, interativa e gratuita na internet, sem a necessidade do usuário realizar down
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 02/04/2012
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35. Efeito do tratamento tÃrmico e do Ãcido salicÃlico na atividade de polifenoloxidase, peroxidase e fenilalanina amÃnia-liase, nas caracterÃsticas fÃsico-quÃmicas e na incidÃncia de patÃgenos em morangos durante o armazenamento / Effect of heat treatment and salicylic acid on polyphenoloxidase, peroxidase and phenylalanine ammonia-liase activity, physical-chemistry characteristics and incidence of pathogens in strawberries during storage
The strawberry is a fruit that is highly perishable and are very susceptible to physical damage and fungal attack. The use of fungicides has been the primary method for reducing post-harvest diseases. Accordingly, alternative methods free of chemicals must be used in post-harvest to maintain the quality and prolong the life reduce the incidence of fungi. The
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 27/02/2012
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36. Antibacterial effect of water-soluble chitosan on representative dental pathogens Streptococcus mutans and Lactobacilli brevis
Dental caries is still a major oral health problem in most industrialized countries. The development of dental caries primarily involves Lactobacilli spp. and Streptococcus mutans. Although antibacterial ingredients are used against oral bacteria to reduce dental caries, some reports that show partial antibacterial ingredients could result in side effects. O
J. Appl. Oral Sci.. Publicado em: 2012-12