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Exploitation of a single interface flow system for on-line aqueous biphasic extraction

SILVESTRE, Cristina I. C.; RODRIGUES, Sofia; SANTOS, Joao L. M.; LIMA, Jose L. F. C.; ZAGATTO, Elias A. G.
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.25%
The exploitation of aqueous biphasic extraction is proposed for the first time in flow analysis This extraction strategy stands out for being environmentally attractive since it is based in the utilization of two immiscible phases that are intrinsically aqueous The organic solvents of the traditional liquid-liquid extractions ale no longer used, being replaced by non-toxic, non-flammable and non-volatile ones. A single interface flow analysis (SIFA) system was implemented to carry out the extraction process due to its favourable operational characteristics that include the high automation level and simplicity of operation, the establishment of a dynamic interface where the mass transfer occurred between the two immiscible aqueous phases, and the versatile control over the extraction process namely the extraction time The application selected to demonstrate the feasibility of SIFA to perform this aqueous biphasic extraction was the pre-concentration of lead. After extraction, lead reacted with 8-hydroxyquinoline-5-sulfonic acid and the resulting product was determined by a fluorimetric detector included in the flow manifold. Therefore, the SIFA single interface was used both as extraction (enrichment) and reaction interface. (C) 2010 Elsevier B.V All rights reserved.; Fundacao para a Ciencia e Tecnologia (FCT)[PTDC/QUI-QUI/105514/2008]; FSE (Ill Quadro Comunitario de Apoio)[SFRH/BD/31107/2006]; FCT/CAPES

Plasmid DNA partitioning and separation using poly(ethylene glycol)/poly(acrylate)/salt aqueous two-phase systems

Johansson, Hans-Olof; Matos, Tiago; Luz, Juliana S.; Feitosa, Eloi; Oliveira, Carla Columbano de; Pessoa Junior, Adalberto; Buelow, Leif; Tjerneld, Folke
Fonte: ELSEVIER SCIENCE BV; AMSTERDAM Publicador: ELSEVIER SCIENCE BV; AMSTERDAM
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.08%
Phase diagrams of poly(ethylene glycol)/polyacrylate/Na2SO4 systems have been investigated with respect to polymer size and pH. Plasmid DNA from Escherichia coil can depending on pH and polymer molecular weight be directed to a poly(ethylene glycol) or to a polyacrylate-rich phase in an aqueous two-phase system formed by these polymers. Bovine serum albumin (BSA) and E. coil homogenate proteins can be directed opposite to the plasmid partitioning in these systems. Two bioseparation processes have been developed where in the final step the pDNA is partitioned to a salt-rich phase giving a total process yield of 60-70%. In one of them the pDNA is partitioned between the polyacrylate and PEG-phases in order to remove proteins. In a more simplified process the plasmid is partitioned to a PEG-phase and back-extracted into a Na2SO4-rich phase. The novel polyacrylate/PEG system allows a strong change of the partitioning between the phases with relatively small changes in composition or pH. (C) 2012 Elsevier B.V. All rights reserved.

Avaliação do método de extração eletroquímica de cloretos para reabilitação de estruturas de concreto com problemas de corrosão de armaduras.; Evaluation of the method of electrochemical extraction of chlorides ions for the rehabilitation of concrete structures with reinforcement corrosion problems.

Monteiro, Eliana Cristina Barreto
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 11/10/2002 Português
Relevância na Pesquisa
36.23%
O presente trabalho avalia o método de extração eletroquímica de íons cloreto na reabilitação de estruturas de concreto com problemas de corrosão de armaduras. Essa metodologia pode ser utilizada para evitar as desvantagens da recuperação tradicional do reparo localizado. No procedimento experimental foram realizados ensaios de laboratório em corpos-de-prova de forma prismática com dimensões reduzidas, moldados com diferentes relações água/cimento. A penetração de cloretos nos corpos-de-prova foi realizada de maneiras distintas: câmara de névoa salina e semiciclos de secagem e imersão parcial. Entre outros aspectos, foi avaliada a influência da espessura de cobrimento e da relação água/cimento na resposta do método através da determinação do teor inicial e final dos íons cloreto.Nas conclusões observa-se que a eficiência desse método foi até superior à encontrada em outros trabalhos da literatura. Nas séries cuja penetração de cloretos se deu através da câmara de névoa salina em média foram removidos 78% dos íons cloreto inicialmente presentes no concreto, nas séries onde a penetração de cloretos foi por semiciclos de secagem e imersão parcial obteve-se 91% de eficiência de remoção.; This present project evaluates the method of electrochemical extraction of chloride ions for the rehabilitation of concrete structures with reinforcement corrosion problems. This methodology can be used to prevent the disadvantages of traditional repair strategies in the patch repair. In the experimental procedure...

Estudo da partição do ácido clavulânico empregando sistemas micelares de duas fases aquosas com adição de sal ou polímero; Study of clavulanic acid partitioning using two-phase aqueous micellar system with salt or polymer addition

Silva, Marcela de Siqueira Cardoso
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: dissertação de mestrado Formato: application/pdf
Publicado em 20/09/2012 Português
Relevância na Pesquisa
36.07%
O ácido clavulânico (AC) é um potente inibidor de ?-lactamases, sendo utilizado em associação com antibióticos ?-lactâmicos. Atualmente, a purificação industrial do AC envolve, principalmente, processos de extração líquido-líquido com solventes orgânicos e etapas cromatográficas. Assim, métodos alternativos como os sistemas micelares de duas fases aquosas (SMDFA), os quais oferecem seletividade na partição de biomoléculas de acordo com sua hidrofobicidade, são de grande interesse. O presente trabalho teve como objetivo estudar a partição do AC em sistemas micelares não iônicos de duas fases aquosas, puros e com adição do sal (NH4)2SO4 ou do polímero sulfato de dextrana (Dx-S). Os estudos de estabilidade do AC mostraram que o fármaco é mais estável em pH 6,5 e temperaturas mais baixas (5 - 20 ºC). Em relação à presença dos aditivos, foi verificado que a adição do Dx-S acarretou em menor perda da estabilidade do AC quando comparado ao (NH4)2SO4, com valor residual ? 90% a 35 °C. Na presença dos tensoativos Triton X-114 e Triton X-100, o AC apresentou-se estável, com valor residual de aproximadamente 100%. De acordo com os ensaios de partição, o AC foi recuperado preferencialmente na fase pobre em micelas...

Avaliação de diferentes sorventes na extração em fase solida de pesticidas em agua : desenvolvimento e validação de metodologia; Evaluation of different sorbents for the solid phase extraction of pesticides in water: development and validation of the methodology

Leonardo Jardim da Silva Faria
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: dissertação de mestrado Formato: application/pdf
Publicado em 19/08/2004 Português
Relevância na Pesquisa
36.31%
Muitos contaminantes orgânicos estão presentes em água em baixas concentrações. Devido a isso, tem crescido o interesse em desenvolver técnicas de preparo de amostra que possibilitem pré-concentrar os analitos presentes na matriz para adequação ao sistema de detecção. Neste trabalho foi empregada a extração em fase sólida (EFS) com diferentes sorventes, tubos de extração C-18 e de poliestireno-divinilbenzeno (PS-DVB) e coluna de PS-DVB, para extrair pesticidas presentes em água. Os pesticidas estudados foram: bentazona, cianazina, simazina, 2,4-D, atrazina, diuron e linuron. Para a separação dos pesticidas utilizou-se a cromatografia líquida de alta eficiência (CLAE), com coluna analítica C-18 Nova Pak-Waters, 150 mm x 3,9 mm d.i., tamanho de partícula de 4 mm e 6 nm de diâmetro de poro. A fase móvel utilizada foi MeOH:H2O 50:50 v/v pH 3,75 (ajustado com ácido fosfórico) e a detecção foi feita por um detector por arranjo de diodos. Na separação cromatográfica obtiveram bons valores de resolução, maiores que 3,0 para todos os pesticidas, os fatores de retenção também foram adequados, estando numa faixa de 1,0 a 14. Os melhores volumes de amostras utilizados na extração foram de 200 mL para tubos C18 ( fator de pré-concentração de 400 vezes ) e de 750 mL para tubos e colunas de PS-DVB ( fator de pré-concentração de 1500 vezes ). A adição de sal na amostra não melhorou os resultados de recuperação para todos os pesticidas em comparação com a amostra isenta de sal. A extração com tubos e colunas de PS-DVB mostrou-se mais adequada para recuperações de pesticidas polares do que os tubos C18...

Avaliação do processo de extração liquido-liquido com a adição de sais para recuperação e purificação de acidos organicos; Evaluation of the liquid-liquid extraction process with salt addition for organic acid recovery and purification

Luciana Lintomen Gitirana
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 13/08/2007 Português
Relevância na Pesquisa
36.36%
Esse estudo objetiva uma avaliação crítica do processo de extração líquido-líquido de ácidos orgânicos, produzidos principalmente por fermentação. Os ácidos orgânicos de interesse nesse trabalho são: ácido cítrico, ácido málico, ácido succínico e ácido tartárico. O estudo engloba, de uma forma geral, a recuperação e a purificação dos ácidos orgânicos selecionados e, para esse propósito, envolve a caracterização termodinâmica dos sistemas envolvidos, a modelagem termodinâmica e a simulação do processo de extração líquidolíquido. Os dados de equilíbrio líquido-líquido foram obtidos a 25oC, e os alcoóis, 2- Butanol e n- Butanol foram avaliados como extratantes, considerando os sistemas ternários e os quaternários, com o efeito ?salting out?, onde o sal MgCl2 foi adicionado. A Modelagem Termodinâmica do equilíbrio líquido-líquido, através do Método de Contribuição de Grupos (UNIFAC-Larsen) e da Modelagem Molecular (NRTL e NRTL Eletrolítico), foi realizada em alguns casos considerando a presença de eletrólitos fortes provenientes da dissociação do sal nos sistemas quaternários, com efeito, ?salting out?; This study aims a critical evaluation of the liquid-liquid extraction process of organic acids...

Estudos do processo de extração liquido-liquido para a purificação do acido acrilico; Study of the liquid extraction process for acrulic acid purification

Alex Barreto Machado
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: dissertação de mestrado Formato: application/pdf
Publicado em 08/08/2007 Português
Relevância na Pesquisa
36.31%
Observa-se que, nos últimos anos, a procura por novos processos de separação para a recuperação de ácidos orgânicos, dentre eles o ácido acrílico, a partir de seu caldo de fermentação, tem sido intensa. O processo de extração líquido-líquido apresenta-se como uma alternativa das mais viáveis para sistemas diluídos, quando se utiliza solventes apropriados e de baixa toxicidade. Na parte computacional do trabalho em questão, inicialmente, realizou-se um estudo do software Aspen Plus no que se refere à obtenção de dados termodinâmicos (parâmetros binários) e curvas binodais. Realizou-se, também, a validação do software obtendo regressões de dados experimentais envolvendo fenol e alguns solventes retirados da literatura. Algumas curvas de extração (curvas binodais), testando diferentes solventes para extração do ácido acrílico, foram construídas. As curvas binodais simuladas no Aspen também auxiliaram na escolha dos pontos experimentais, uma vez que, desta maneira, já se conhecia a região de formação de duas fases dos sistemas em estudo e pôde-se orientar a coleta destes dados laboratoriais sem o consumo excessivo de reagentes e de tempo. A parte experimental deste projeto envolve a obtenção de dados de ELL dos sistemas ternários ácido acrílico - água e os seguintes solventes: diisopropil éter...

Recovery of endo-polygalacturonase using polyethylene glycol-salt aqueous two-phase extraction with polymer recycling

Wu, You-Ting; Pereira, Martinha; Venâncio, Armando; Teixeira, J. A.
Fonte: Kluwer Academic Publishers Publicador: Kluwer Academic Publishers
Tipo: Artigo de Revista Científica
Publicado em /07/2000 Português
Relevância na Pesquisa
36.12%
The partitioning behaviour of endo-polygalacturonase (endo-PG) and total protein from a clarified Kluyveromyces marxianus fermentation broth in polyethylene glycol (PEG)-ammonium sulfate and PEG-potassium phosphate (pH=7) aqueous two-phase systems was experimentally investigated. Both the enzyme and total protein partitioned in the bottom phase for these two kinds of systems. The enzyme partitioning coefficient can be lower than 0.01 in PEG8000-(NH4)2SO4 ATPS with a large phase volume ratio and a moderate tie-line length, which implies the possibility of concentration operation using aqueous two phase partitioning. An ion-exchange separation of high purification efficiency was applied to analyze the clarified and dialyzed fermentation broth. A total purification factor of only 2.3 was obtained, which indicated the high enzyme protein content in the total protein of the fermentation broth. Consequently, the main purpose for separating endo-PG is concentration rather than purification. A separation scheme using an aqueous two-phase extraction process with polymer recycling and a dialysis was proposed to recover endo-PG from the fermentation supernatant of K. marxianus for commercial purpose. A high enzyme recovery up to 95% and a concentration factor of 5 to 8 with a purification factor of about 1.25 were obtained using the single aqueous two-phase extraction process. More than 95% polymer recycled will not affect the enzyme recovery and purification factor. Dialysis was used mainly to remove salts in the bottom phase. The dialysis step has no enzyme loss and can further remove small bulk proteins. The total purification factor for the scheme is about 1.7.; Fundação para a Ciência e Tecnologia (FCT) - PRAXIS XXI. CEC (INCO-DC) - contract number ERB IC18 CT97 0182.

Purification of plasmid DNA vectors by aqueous two-phase extraction and hydrophobic interaction chromatography

Trindade, Inês P.; Diogo, Maria M.; Prazeres, Duarte M. F.; Marcos, João Carlos
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2005 Português
Relevância na Pesquisa
36.15%
The current study explores the possibility of using a polyethyleneglycol(PEG)/ammonium sulphate aqueous two-phase system (ATPS) as an early step in a process for the purification of a model 6.1 kbp plasmid DNA (pDNA) vector. Neutralised alkaline lysates were fed directly to ATPS. Conditions were selected to direct pDNA towards the salt-rich bottom phase, so that this stream could be subsequently processed by hydrophobic interaction chromatography (HIC). Screening of the best conditions for ATPS extraction was performed using three PEG molecular weights (300, 400, 600) and varying the tie-line length, phase volume ratio and lysate load. For a 20 % (w/w) lysate load, the best results were obtained with PEG 600 using the shortest tie-line (38.16 % w/w). By further manipulating the system composition along this tie-line in order to obtain a top/bottom phase volume ratio of 9.3 (35 % w/w PEG 600, 6% w/w NH4)2SO4), it was possible to recover 100 % of pDNA in the bottom phase with a 3-fold increase in concentration. Further increase in the lysate load up to 40 %(w/w) with this system resulted in a 8-fold increase in pDNA concentration, but with a yield loss of 15 %. The ATPS extraction was integrated with HIC and the overall process compared with a previously defined process that uses sequential precipitations with isopropanol and ammonium sulphate prior to HIC. Although the final yield is lower in the ATPS-based process the purity grade of the final pDNA product is higher. This shows that it is possible to substitute the time-consuming two-step precipitation procedure by a simple ATPS extraction.; Portuguese Ministry of Science and Technology - POCTI/BIO/47245/2002.

Solvent extraction of sodium chloride from codfish (Gadus morhua) salting processing wastewater

Ferraro, Vincenza; Cruz, Isabel B.; Jorge, Ruben Ferreira; Pintado, Manuela E.; Castro, Paula M. L.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2011 Português
Relevância na Pesquisa
56.61%
Codfish is worldwide mostly consumed salt-cured due to the highly appreciated sensory characteristics promoted by salt. During the salting process huge amounts of salted wastewater are generated – approximately 22% w/w of the codfish – carrying ca. 250 g/L of sodium chloride and ca. 10 g/L of organic compounds, namely proteins and free amino acids. In this study, the salt load of wastewater generated during the salting process of codfish (Gadus morhua) was successfully reduced by ethanol extraction. The effects of time, sample:ethanol ratio, pH and temperature on salt extraction by ethanol addition were assessed by a onevariable-at-a-time approach and then by performing a 32 fractional factorial design. The effects of pH were also assessed in absence of ethanol. The maximum amount of salt precipitated in the wastewater was ca. 33%, at a wastewater-ethanol ratio 1:1 (v/v), at a temperature of 0 °C and after 30 min. Proteins and free amino acids present in the wastewater significantly limited salt precipitation; in a blank solution (salt in water at ca. 250 g/L) a higher amount of salt, ca. 37%, was precipitated in the same conditions. Ethanol and temperature showed a linear effect on salt precipitation for both wastewater and blank solution however ethanol was the driving factor. Changes in pH did not result in salt precipitation either in absence or presence of ethanol. During salt extraction...

Extraction of added-value products from biomass using ionic liquids; Extração de produtos de valor acrescentado a partir de biomassa utilizando líquidos iónicos

Silva, Ana Filipa Martins Cláudio da
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
36.07%
The main purpose of this thesis is to investigate the potential of ionic liquids (ILs) as a new class of extractive solvents for added-value products from biomass. These include phenolic compounds (vanillin, gallic, syringic and vanillic acids), alkaloids (caffeine) and aminoacids (L-tryptophan). The interest on these natural compounds relies on the wide variety of relevant properties shown by those families and further application in the food, cosmetic and pharmaceutical industries. Aiming at developping more benign and effective extraction/purification techniques than those used, a comprehensive study was conducted using aqueous biphasic systems (ABS) composed of ILs and inorganic/organic salts. In addition, ILs were characterized by a polarity scale, using solvatochromic probes, aiming at providing prior indications on the ILs affinity for particular added-value products. Solid-liquid (S-L) extractions from biomass and using aqueous solution of ILs were also investigated. In particular, and applying and experimental factorial design to optimize the operational conditions, caffeine was extracted from guaraná seeds and spent coffee. With both types of extractions it was found that it is possible to recover the high-value compounds and to recycle the IL and salt solutions. Finally...

Mobility of metals in salt marsh sediments colonised by Spartina maritima (Tagus estuary, Portugal)

Reboreda, Rosa; Caçador, Isabel; Pedro, Sílvia; Almeida, Pedro R.
Tipo: Artigo de Revista Científica Formato: 450783 bytes; application/pdf
Português
Relevância na Pesquisa
36.13%
Chemical associations of Zn, Pb, Cu, Co and Cd were determined using a sequential extraction procedure in sediments colonised by S. maritima in three salt marshes within the Tagus estuary: Rosa´rio, Corroios and Pancas. Concentrations of these metals were also analysed in above- and belowground parts of Spartina maritima, as well as in sediments colonised by the plant. The highest metal concentrations in sediments were found in the marshes near the industrial and urban areas, whereas metal concentrations in plants were not significantly different among sites. This was thought to be a consequence of differences observed in metal bioavailability: Metals in Pancas, the least polluted location, were largely associated to easily accessible fractions for plant uptake, probably as a result of low organic matter content and high sandy fraction in sediments. S. maritima was able to induce the concentration of metals between its roots in the three salt marshes. The results obtained in this study indicate that S. maritima could be useful to induce phytostabilisation of metals in sediments, although the effectiveness to modify chemical associations is highly dependent on existing sediment parameters, and thus different results could be obtained depending on site characteristics.

Aqueous biphasic system based on cholinium ionic liquids: extraction of biologically active phenolic acids

Branco, Sónia Isabel Pereira
Tipo: info:eu-repo/semantics/masterthesis
Publicado em /09/2014 Português
Relevância na Pesquisa
36.18%
Phenolic acids are aromatic secondary plant metabolites, widely spread throughout the plant kingdom. Due to their biological and pharmacological properties, they have been playing an important role in phytotherapy and consequently techniques for their separation and purification are in need. This thesis aims at exploring new sustainable separation processes based on ionic liquids (ILs) in the extraction of biologically active phenolic acids. For that purpose, three phenolic acids with similar chemical structures were selected: cinnamic acid, p-coumaric acid and caffeic acid. In the last years, it has been shown that ionic liquids-based aqueous biphasic systems (ABSs) are valid alternatives for the extraction, recovery and purification of biomolecules when compared to conventional ABS or extractions carried out with organic solvents. In particular, cholinium-based ILs represent a clear step towards a greener chemistry, while providing means for the implementation of efficient techniques for the separation and purification of biomolecules. In this work, ABSs were implemented using cholinium carboxylate ILs using either high charge density inorganic salt (K3PO4) or polyethylene glycol (PEG) to promote the phase separation of aqueous solutions containing three different phenolic acids. These systems allow for the evaluation of effect of chemical structure of the anion on the extraction efficiency. Only one imidazolium-based IL was used in order to establish the effect of the cation chemical structure. The selective extraction of one single acid was also researched. Overall...

Determination of triamterene in human plasma and urine after its cloud point extraction

Tabrizi,Ahad Bavili; Naini,Sana; Parnian,Kosar; Mohammadi,Samin; zad,Fayeze Emami; Anvarian,Samira Pourtaghi; Abdollahi,Ali
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2014 Português
Relevância na Pesquisa
36.15%
A new analytical approach was developed involving cloud point extraction (CPE) and spectrofluorimetric determination of triamterene (TM) in biological fluids. A urine or plasma sample was prepared and adjusted to pH 7, then TM was quickly extracted using CPE, using 0.05% (w/v) of Triton X-114 as the extractant. The main factors that affected the extraction efficiency (the pH of the sample, the Triton X-114 concentration, the addition of salt, the extraction time and temperature, and the centrifugation time and speed) were studied and optimized. The method gave calibration curves for TM with good linearities and correlation coefficients (r) higher than 0.99. The method showed good precision and accuracy, with intra- and inter-assay precisions of less than 8.50% at all concentrations. Standard addition recovery tests were carried out, and the recoveries ranged from 94.7% to 114%. The limits of detection and quantification were 3.90 and 11.7 µg L-1, respectively, for urine and 5.80 and 18.0 µg L-1, respectively, for plasma. The newly developed, environmentally friendly method was successfully used to extract and determine TM in human urine samples.

Optimization of extraction and determination of chloramphenicol in livestock meat samples using aqueous two-phase system of n-propanol and potassium citrate coupled with HPLC

Li,Yanfang; Han,Juan; Wang,Yun; Ma,Jingjing; Yan,Yongsheng; Cao,Lihua
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2013 Português
Relevância na Pesquisa
36.28%
An aqueous two-phase system (ATPS) based on short chain alcohol and salt was the method for preconcentration, separation and analysis of chloramphenicol (CAM), coupled with high performance liquid chromatography with ultraviolet-visible detector (HPLC-UV). In order to select the suitable ATPS for CAM extraction, different ATPSs were tested and n-propanol/potassium citrate ATPS was chosen for separating and concentrating CAM in the subsequent experiments. The influences of the salt concentration, pH and the volume of n-propanol on the extraction efficiency and partition coefficient of CAM were examined. Response surface methodology was employed to optimize the experimental conditions. Under the optimal conditions, this method has been applied to quantitative determination of CAM in livestock meat samples with limit of detection of 0.48 ng g-1 and limit of quantification of 1.6 ng g-1 with a recovery range of 92.39-104.12%. This ATPS used low cost of organic solvents and supplied a moderate and biocompatible environment, which is suitable for biomolecules.

Preconcentration and determination of cadmium in water and food samples by in situ surfactant-based solid-phase extraction and flame atomic absorption spectrometry

Jamali,Mohammad Reza; Boromandi,Afsaneh
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2014 Português
Relevância na Pesquisa
36.18%
In situ surfactant-based solid-phase extraction (ISS-SPE) is proposed as a preconcentration procedure for the determination of cadmium in water and food samples by flame atomic absorption spectrometry. In the present work, cetyltrimethylammonium bromide was used as a cationic surfactant, hexafluorophosphate ion as an ion-pairing agent and 4-benzylpiperidinedithiocarbamate potassium salt (K-4-BPDC) as a chelating agent. Several variables that affect the extraction efficiencies such as pH, type and amount of surfactant, concentration of ion-pairing agent, concentration of chelating agent, ionic strength and extraction time were investigated and optimized. After optimization of the complexation and extraction conditions, an enrichment factor of 40 was obtained. The calibration curve was linear in the range of 1-50 µg L-1 and the limit of detection was 0.3 µg L-1. The relative standard deviation for 20 µg L-1 of cadmium was lower than 2.2%. Validation of the methodology was performed by standard addition method and analysis of certified reference materials. The method was successfully applied to the determination of cadmium in various food and water samples.

Batch and continuous extraction of bromelain enzyme by reversed micelles

Fileti,Ana Maria Frattini; Fischer,Gilvan Anderson; Santana,José Carlos Curvelo; Tambourgi,Elias Basile
Fonte: Instituto de Tecnologia do Paraná - Tecpar Publicador: Instituto de Tecnologia do Paraná - Tecpar
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2009 Português
Relevância na Pesquisa
36.15%
The main aim of this study was to optimize the conditions for bromelain extraction by reversed micelles from pineapple juice (Ananas comosus). The purification was carried out in batch extraction and a micro-column with pulsed caps for continuous extraction. The cationic micellar solution was made of BDBAC as a surfactant, isooctane as a solvent and hexanol as a co-solvent. For the batch process, a purification factor of 3 times at the best values of surfactant agent, co-solvent and salt concentrations, pH of the back and forward extractions were, 100 mM, 10% v/v, 1 M, 3.5 and 8, respectively. For the continuous operation, independent variables optimal point was determined: ratio between light phase flow rate and total flow rate equal to 0.67 and 1 second for the time interval between the pulses. This optimal point led to a productivity of 1.29 mL/min and a purification factor of 4.96.

Simultaneous determination of Pb and Cd in seafood by ICP OES with on-line pre-concentration by solid phase extraction with amberlite XAD-4 after complex formation with DDTP

Santos,Éder José dos; Santos,Arlene Bispo dos; Herrmann,Amanda Beatriz; Kulik,Suzete; Baika,Loana Mara; Tormen,Luciano; Curtius,Adilson José
Fonte: Instituto de Tecnologia do Paraná - Tecpar Publicador: Instituto de Tecnologia do Paraná - Tecpar
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2013 Português
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35.99%
An on-line method for Cd and Pb pre-concentration and simultaneous determination in acid digested seafood by inductively coupled plasma optical emission spectrometry (ICP OES) was developed. The on-line pre-concentration was based on the complex formation of the analytes with the ammonium salt of O,O-diethyldithiophosphate (DDTP) and using the Amberlite XAD-4 resin as a solid support in a homemade column. Different conditions of the flow injection system, such as solutions flow rates, nebulizer pressure and eluent concentration were optimized. Three certified reference materials of lobster hepatopancreas, dogfish liver and fish protein, three samples of fish muscle and three samples of shrimp were digested with HNO3, H2O2 and H2SO4 in a microwave system under reflux. DDTP was added in the solutions obtained, and the mixture was injected in the FI system. Calibration curves for Cd and Pb were obtained using the standard solutions in the concentration range 0.05-0.5 µg mL-1 in the digestion medium, submitted to the same pre-concentration procedure. The quantification limits (3.3 x LOD) for 5 min of pre-concentration time were 0.005 mg kg-1 Cd2+ and 0.1 mg kg-1 Pb2+ in the sample of fish or shrimp in natura, considering 1.0 g of the sample in a final volume of 50 mL. The agreement of the obtained concentrations with the certified ones (Student t-test...

Low ionic strength extraction of nuclease-treated nuclei destroys the attachment of transcriptionally active DNA to the nuclear skeleton.

Razin, S V; Yarovaya, O V; Georgiev, G P
Tipo: text
Publicado em 25/10/1985 Português
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We have studied how the conditions in which the nuclear matrix is isolated influence the association of transcribing DNA with the nuclear matrix. Extraction of nuclease-treated nuclei with a low ionic strength solution before a high salt nuclei with a low ionic strength solution before a high salt extraction completely abolishes this association. However, RNA removal by RNAase treatment does not affect the binding of transcribing DNA to the nuclear matrix. The nature of the association of active genes with the nuclear matrix is discussed.

Canola Proteins for Human Consumption: Extraction, Profile, and Functional Properties

Tan, Siong H; Mailer, Rodney J; Blanchard, Christopher L; Agboola, Samson O
Fonte: Blackwell Publishing Inc Publicador: Blackwell Publishing Inc
Tipo: text
Publicado em /01/2011 Português
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Canola protein isolate has been suggested as an alternative to other proteins for human food use due to a balanced amino acid profile and potential functional properties such as emulsifying, foaming, and gelling abilities. This is, therefore, a review of the studies on the utilization of canola protein in human food, comprising the extraction processes for protein isolates and fractions, the molecular character of the extracted proteins, as well as their food functional properties. A majority of studies were based on proteins extracted from the meal using alkaline solution, presumably due to its high nitrogen yield, followed by those utilizing salt extraction combined with ultrafiltration. Characteristics of canola and its predecessor rapeseed protein fractions such as nitrogen yield, molecular weight profile, isoelectric point, solubility, and thermal properties have been reported and were found to be largely related to the extraction methods. However, very little research has been carried out on the hydrophobicity and structure profiles of the protein extracts that are highly relevant to a proper understanding of food functional properties. Alkaline extracts were generally not very suitable as functional ingredients and contradictory results about many of the measured properties of canola proteins...