Navegando por Assunto "Cromatografia gasosa"

Agora exibindo 1 - 3 de 3

Acesso aberto (Open Access)
Chemometric identification and nutritional evaluation of three species of Lutjanidae (Perciformes) from the Amazonian Atlantic Coast based on fatty acid profiles
(Instituto Nacional de Pesquisas da Amazônia, 2016-12) ALMEIDA, Edilene Santos de; SILVA, Evaldo Martins da
The fatty acid (FA) profiles of fish species with a similar genetic or geographic origin are important quality parameters that attract bioecological interest because they are inﬂuenced by the nutritional habits of the species. The aim of this study was to determine the proximate compositions and FA profiles of heart, brain and muscle tissues from three fish species (Lutjanus purpureus, Lutjanus synagris and Ocyurus chrysurus) captured from the Amazonian Atlantic Coast. In addition to performing nutritional analysis of the FA profiles, principal components analysis (PCA) was performed as a chemometric tool to discriminate among the species. Lutjanus synagris had the highest protein content (18.23%), while O. chrysurus possessed the highest lipid content (4.25%). All of the nutritional quality parameters (the n-6/n-3 and Σ polyunsaturated FA/Σ saturated FA ratios and dietary indices of atherogenicity and thrombogenicity) of the FA profiles of the three species are of interest to consumers. In general, the predominant FA in the tissues of all species analyzed was palmitic acid, followed by stearic acid. Oleic acid was predominant among the monounsaturated FAs, while docosahexaenoic acid was the most prevalent polyunsaturated FA. Chemometric analysis was an effective tool for fish identification. PCA showed that the FA profiles of the brain tissues were optimal for discriminating among the species, with O. chrysurus showing the most different FA profile from the others. The muscle FA profile was the most useful for identifying L. purpureus.
Acesso aberto (Open Access)
Estudo da qualidade da gasolina tipo A e sua composição química empregando análise de componentes principais
(2014) CARVALHO, Fabio Israel Martins; DANTAS FILHO, Heronides Adonias
The type A gasoline samples were analyzed by gas chromatography with flame ionization detector (GC-FID) which allowed quantifying and classifying of the various compounds into different classes of hydrocarbons. Several physicochemical parameters were evaluated according to the official methods in order to compare the results obtained against the limits established by the Agência Nacional de Petróleo, Gás Natural e Biocombustíveis (ANP, 2011). Additionally, principal component analysis (PCA) was applied to discriminate the samples studied, which revealed the separation of four groups according to their chemical composition determined in samples collected from the eight fuel distributors in the State of Pará.
Acesso aberto (Open Access)
Um método fuzzy para programação de inspeções em transformadores baseado na análise de gases combustíveis e parâmetros físico-químicos do óleo isolante
(Universidade Federal do Pará, 2014-10-24) PANTOJA, Márcia Priscila Furtado; OLIVEIRA, Terezinha Ferreira de; http://lattes.cnpq.br/6230804143692945; SILVEIRA, Antônio Morais da; http://lattes.cnpq.br/7549503749842625
Power transformers using oil for insulation internal parts need periodic maintenance of a program aimed at detecting possible failures, such as deterioration of the winding insulation cellulose, short circuit between turns, gases dissolved in the oil due to its degeneration etc. Typically, preventive maintenance programs are used by companies for generation, transmission and distribution of electricity for avoiding these failures may result in removal of equipment from the electrical system, a situation that involves large financial losses, either by decreased billing at payment of penalties to the regulatory agency, as well as reduced system reliability. To avoid these types of losses, this paper presents a proposed solution using fuzzy approach, to assist the process of inspections programming in high power transformers (500kv), through the analysis of gases dissolved in insulating oil, obtained by the technique gas chromatography and physico-chemical analysis of the oil. We attempted to produce a solution that combines the results of traditional methods already established in the literature, with additional situations originating from the physico-chemical analysis of the oil and knowledge of experts in order to increase the effectiveness of such equipment inspection procedure. With this, any Electric Power System - SEP - that performs diagnostics on transformers by NBR 7274, tends to get a more accurate diagnosis, due to the association of physical-chemical analysis of the insulating oil with gas chromatography and knowledge tacit from specialists, enabling us to expand the base of original rules of that technical standard. All tests and the database used were from a laboratory of Chemistry of various electrical substations of an power company located in Barcarena - Pará - Brazil.