996 resultados para Ácido pirazina tetracarboxílico
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The amount of waste generated by industries has increased gradually in recent years. The proper disposal of residues has been an area of study of many researchers. Several organic compounds are considered potential contaminants of natural waters due to their high toxicity, difficult natural degradation and long persistence in the environment. Ways of recovery and reutilization as well as concepts that minimize the generation of wastes have been increasing widely. Organometallic compound of pyrazine carboxylic acid has proven to be of great interest in many areas. Herein, we studied the use of pyrazine tetracarboxylic acid ligand for complex formation with iron (Fe). The binder (C 8H4N2O8) was synthetized with the addition of Fe (complex) and tested as a catalyst in oxidation reactions of the organic model compound methylene blue (MB). Tetramethyl pyrazine was used in the synthesis, which was oxidized with potassium permanganate in order to form the ligand. The ligand (C 8H4N2O8) was then characterized to validate its formation. For the complex solution, it was used (C 8H4N2O8) and Fe (NO3)3.9H2O 0,01molL-1. After preliminary tests, it was found that the best ratio of Fe and the ligand was 2: 1. Through the oxidation tests, it could be seen that the complex has great potential for the degradation of different concentrations of MB. During only 20 minutes of reaction, approximately 60% of MB 500 mgL -1 was oxidized. The use of the complex was found to be an attractive alternative for oxidation of effluents with high organic compounds levels and contributes to the minimization of organic contaminants hazards in the environment.
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The aim of this work was to develop and to validate a methodology using HPLC for the simultaneous determination of folates and folic acid in foods. The limits of detection and the recovery rates for the vitamins in the certified reference materials were respectively 5 pg/mL and 94-108% for 5-MTHF, 7 pg/mL and 97-102% for THF, 30 pg/mL and 97.9-104% for 5-FTHF, 30 pg/mL and 95-107 for 10-FFA, 5 ng/mL and 97-102% for FA and 5 ng/mL and 98-103% for 10-MFA. Repeatability showed a coefficient of variation below 3.9% for all the vitamins. The proposed methodology was shown to be efficient when applied to different certified reference materials, namely pig's liver (BCR487), powdered milk (BCR421) and a vegetable mixture (BCR485).
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This paper proposes a methodology for spectrophotometric determination of hexamethylenetetramine (HMT) by using chromotropic acid in a phosphoric acid media employing a domestic microwave oven as a source of heating. The reddish-purple soluble product is quantitatively formed after 30 s of irradiation and obeys the Beers law in the range between 0.1-1.2 mg L-1 HMT (r = 0.99925). The method was applied successfully in commercial pharmaceutical preparations containing dyes in their composition. The results showed that the method proposed is feasible for simplicity, speed, low cost, precision and accuracy when compared with United States Pharmacopeia official method.
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The copolymer poly (L-co-D,L lactic acid), PLDLA, has gained prominence in the field of temporary prostheses due to the fact that their time of degradation is quite compatible with the requirement in the case of osseous fracture. In this work the in vivo degradation of devices from copolymer, as a system of plates and screws, used in fixation of the tibia of rabbits was studied. The devices were implanted in 15 adult rabbits, albinos, New Zealand race, and they were used as control devices of alloys of titanium (Ti-6Al-4V/ V grade). The use of copolymers, synthesized in the laboratory, was tested in the repair of fracture in rabbits'tibias, being assessed in the following times: 2 weeks, 2 months and 3 months. Morphological analysis of tissue surrounding the plate and screw system, for 2 weeks of implantation, showed the presence of osteoblasts, indicating a pre bone formation. After 2 months there was new bone formation in the region in contact with the polymer. This bone growth occurred simultaneously with the process of PLDLA degradation, invading the region where there was polymer and after 3 months there was an intense degradation of the copolymer and hence greater tissue invasion compared to 2 months which characterized bone formation in a region where the polymer degraded. The in vivo degradation study of the devices for PLDLA by means of histological evaluations during the period of consolidation of the fracture showed the efficiency of plate and screw system, and it was possible to check formation of bone tissue at the implantation site, without the presence of inflammatory reaction
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Hyaluronic acid is a polysaccharide of the glycosaminoglycan family present in mammal tissues. In the eye, it can be found in the cornea, the sclera and the vitreous humor. Currently, it has been employed in several medical specialties, including ophthalmology. The objective of this paper is to demonstrate the various current and future ophthalmic applications of this substance.
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Universidade Estadual de Campinas. Faculdade de Educao Fsica
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Um experimento foi conduzido com o objetivo de avaliar os efeitos da incluso de cido benzoico (Vevovitall) na dieta sobre o desempenho e a morfologia intestinal do duodeno de leites de 28 a 70 dias de idade. Foram utilizados 160 leites Dalland Penarlan desmamados aos 21 dias de idade, separados por sexo. O experimento foi dividido em fases pr-inicial 1 (28 a 35 dias de idade), pr-inicial 2 (36 a 46 dias de idade) e fase inicial (47 a 70 dias idade). Utilizou-se o delineamento experimental tipo blocos ao acaso com 5 tratamentos, cada um com 8 repeties de 4 animais, totalizando 40 unidades experimentais. Foram utilizados quatro nveis de cido benzoico (0; 0,25; 0,50 e 0,75%) e um tratamento testemunha com cido fumrico. Abateram-se, aos 70 dias de idade, dois animais por repetio para coleta de amostras do duodeno e estudo da morfologia intestinal e um animal por repetio para estudo de leses gstricas. Foram avaliadas as caractersticas de desempenho (ganho de peso, consumo de rao e converso alimentar) para cada fase e para o perodo total. Como caractersticas morfolgicas, foram avaliadas a altura das vilosidades, a profundidade de criptas e a relao altura de vilosidades/profundidade de criptas. Avaliou-se ainda a incidncia de diarreia. No perodo de 28 a 70 dias, o uso de cido benzoico influencia o desempenho de sunos, que neste estudo foi melhor os nveis de 0,50 e 0,75%, e reduz a incidncia de diarreia. Animais alimentados com dietas contendo cido benzoico apresentam maior altura de vilosidade e profundidade de criptas.
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INTRODUO: A auto-enxertia de nervo considerada tratamento de escolha nas grandes perdas de tecido neural que no permitam a reparao atravs de anastomose primria. Nesses casos, o tubo sinttico base de cido poligliclico uma alternativa para enxertia de nervo. Por outro lado, muitos estudos tm enfatizado a importncia dos fatores neurotrficos na regenerao neural: o monossialotetraesosilgangliosdeo (GM1), um dos principais glicoesfingolpides do tecido nervoso de mamferos, tido como potencializador dos efeitos desses fatores. OBJETIVO: Comparar, em ratos, o grau de regenerao neural, utilizando anlise histolgica, contagem do nmero de axnios mielinizados regenerados e anlise funcional com a utilizao do neurotubo e do GM1. MTODOS: Essa avaliao foi obtida com a interposio de enxerto autgeno (grupo A), tubo de cido poligliclico (grupo B) e da associao do tubo de cido poligliclico administrao de GM1 (grupo C) em defeitos de 5 mm no nervo citico. RESULTADOS: Foi observada formao de neuroma apenas no grupo A. Os grupos A e C apresentaram padres histolgicos semelhantes, exceto que os axnios regenerados do grupo C apresentavam-se mais organizados e mielinizados que o grupo A. CONCLUSO: Na recuperao funcional, no houve diferena estatisticamente significativa entre os trs grupos, a despeito das diferenas histolgicas qualitativas e quantitativas verificadas.
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The polyelectrolyte complex (PEC) resulting from the reaction of sodium carboxymethylcellulose (CMC) and N,N,N-trimethylchitosan hydrochloride (TMQ) was prepared and then characterized by infrared spectroscopy and energy dispersive X rays analysis. The interactions involving the PEC and Cu2+ ions, humic acid and atrazine in aqueous medium were studied. From the adsorption isotherms the maximum amount adsorbed (Xmax) was determined as 61 mg Cu2+/g PEC, 171 mg humic acid/g PEC and 5 mg atrazine/g PEC. The results show that the CMC/TMQ complex has a high affinity for the studied species, indicating its potential application to remove them from aqueous media.
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The present article reviews different aspects of the chemistry of two widely used β-lactam antibiotics Clavulanic Acid and Cephamycin C. The article discusses important details of the biosynthesis of these compounds, their action mechanism and, principally, the methods employed in their isolation and purification, in accordance with the available literature. Despite the large quantity of available articles and patents concerning β-lactam antibiotics, those which describe the isolation and purification of Clavulanic Acid and Cephamycin C are rare. Overall, the intention of this article is to discuss the up-to-date scientific research related to the compounds under review.
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Alkaline salts of the palmitic acid were synthesized and characterized from aqueous and ethanolic medium. The salts were characterized by elemental analysis (EA) and infrared spectroscopy (IR). EA and IR, being its synthesis comproved, also characterized the ethyl palmitate. All the salts and the ester were submitted to thermal analysis using thermogravimetry (TG), and differential thermal analysis (DTA) in the temperature ranging from room to 700 C under air dynamic atmosphere. Differential scanning calorimetry (DSC) measurements were taken from -90 C up to temperatures close to the starting of the decomposition temperature, determined by thermogravimetry, using heating and cooling cycles.
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Docosahexaenoic acid (C22:6, n-3, DHA) is a polyunsaturated fatty acid (PUFA) present in large concentrations in the brain and, due to the presence of six double bonds in its structure, is highly susceptible to oxidation by enzymes and reactive oxygen/nitrogen species. The peroxidation of PUFAs has been implicated in an increasing number of human disorders, including neurodegenerative diseases. Hence, a better understanding of the metabolism pathways of DHA should provide new insights about its role in neurodegenerative diseases. Here we review the main aspects related to DHA metabolism, as well as, the recent findings showing its association with neurodegenerative diseases.
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The determination of acetic acid in vinegar adulterated sample using simultaneous potentiometric and condutometric titrations was used as an example of integrated experiment in instrumental analysis. An Excel spreadsheet, which allows the entry of simultaneous data and the construction of the superimposed experimental curves (condutometric, potentiometric, first and second derivative potentiometric curve and, distribution diagrama of the acetic species as function of pH), was used as powerful tool to discuss the fundamental concepts involved in each technique and choose the best of them to quantify, without mutual interference, H3CCOOH and HCl in vinegar adulterated sample.
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O presente estudo investigou fatores scio-demogrficos, de estilo de vida e gineco-obsttricos associados s concentraes sricas ou plasmticas de homocistena, cido flico, vitaminas B12 e B6 em mulheres de baixa renda de So Paulo, Brasil. Concentraes sricas de cido flico e vitamina B12 foram analisadas por fluoroimunoensaio; concentraes plasmticas de homocistena e vitamina B6, por cromatografia lquida de alta performance em fase reversa. Variveis independentes foram inicialmente selecionadas segundo pressupostos tericos, correlao de Pearson ou teste Kruskal-Wallis (p < 0,20). Concentraes alteradas segundo pontos de corte para homocistena, cido flico, vitaminas B12 e B6 foram observadas em 20%, 6%, 11% e 67% das participantes, respectivamente. Idade foi positivamente correlacionada vitamina B6 e homocistena plasmticas (p < 0,001). ndice de massa corporal foi positivamente correlacionado vitamina B6 plasmtica (p < 0,001). Modelos de regresso linear mltiplos explicaram 10,2%, 5,8%, 14,4% e 9,4% das concentraes de cido flico, vitamina B12, vitamina B6 e homocistena, respectivamente. No presente estudo, variveis scio-demogrficas, de estilo de vida e gineco-obsttricas apresentaram contribuio importante na variao das concentraes dos indicadores bioqumicos avaliados.
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A mudana no mercado global do petrleo nos ltimos anos, com o declnio das reservas de leo leve, tm forado a busca por novos campos petrolferos em ambientes mais remotos, como nos campos localizados na camada pr-sal, e a explorao de leos pesados que possuem elevado teor de cidos naftnicos. Isso acarreta em grandes desafios para a previso do desempenho de materiais frente s novas condies ambientais em que esto inseridos. No presente trabalho, o comportamento da corroso do ao carbono AISI 1010 e do ao inoxidvel AISI 316L foi estudado em solues aquosas com elevado teor de cloreto e em soluo de cido naftnico ciclopentanico a fim de ter melhor entendimento da ao dessas espcies no processo de corroso e simular a corroso pela gua de produo na indstria petrolfera. Foram aplicadas as tcnicas de potencial de circuito aberto, polarizao potenciodinmica, voltametria cclica, espectroscopia de impedncia eletroqumica, espectroscopia Raman, microscopia eletrnica de varredura e microscopia de fora atmica, usadas, em cada caso, de acordo com a convenincia. O aumento da [Cl-] na faixa de 1,22,8 mol.L-1 no altera os processos catdicos e andicos perto do Ecorr para os aos AISI 1010 e AISI 316L. Em condies de sobrepotenciais afastados do Ecorr, o aumento de [Cl-] aumenta os processos oxidativos de corroso, o que expresso pelas maiores densidades de corrente e carga andica e aumento da perda de massa sofrida pelos eletrodos de ambos os aos. Portanto, os danos da corroso so mais intensos quando se aumenta a [Cl-]. O ao AISI 1010 ativo nas solues de NaCl e a corroso se propaga livremente de forma uniforme. Para o ao AISI 316L, uma ampla faixa de passividade pode ser vista nas solues de NaCl; no Epit ocorre a ruptura do filme passivo e o crescimento de pites estveis. Aps 24 h de imerso em solues de sulfato de sdio (branco) e de cido naftnico ciclopentanico ocorre crescimento de filme de xido e as fases -Fe2O3, Fe3O4 e -FeO(OH) foram identificadas nos espcimes de ao AISI 1010 e Fe3O4 foi identificado nos defeitos do filme prvio presente na superfcie do ao AISI 316L. Os filmes formados em soluo de cido ciclopentanico possuem menor resistncia polarizao, maior rugosidade e maior taxa de corroso quando comparado aos filmes crescidos na soluo branco, para ambos os aos. A presena do cido naftnico muda a forma como a reao de corroso se procede e contribui para o aumento da corroso. A corroso naftnica foi mais pronunciada no ao carbono porque a presena dos elementos de liga no ao inox reduzem o nmero de stios ativos ricos em Fe e tornam menos oportuna a ligao do Fe com o naftenato.
