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Caracterização bioquímica das ß-glucosidases do Scytalidium thermophilum; Biochemical characterization of ß-glucosidases from Scytalidium thermophilum

Zanoelo, Fabiana Fonseca
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 24/03/2005 PT
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A celulose é a mais abundante fonte de carbono presente na madeira e nos resíduos agrícolas, e a sua hidrólise completa é realizada pela ação sinergística de diferentes enzimas, como: as endo-1,4-ß-D-glucanase, exo-1,4-ß-glucanase e ß-glucosidase ou celobiase. O presente trabalho descreve algumas propriedades fisiológicas e bioquímicas do sistema ß-glucosidásico do fungo termofílico Scytalidium thermophilum. Tal fungo foi isolado originalmente do solo da Índia e gentilmente cedido pelo Dr. G. Straastma (Holanda). O meio M8 favoreceu a produção das ß-glucosidases. Entre os açúcares testados como fonte de carbono, avicel e celobiose foram os melhores indutores das ß-glucosidases extracelular e micelial. Quando o fungo foi crescido em dois estágios, observou-se inicialmente a repressão da síntese por glicose e a indução por avicel ou celobiose. Utilizando-se ciclo-heximida, observou-se a síntese "de novo" das proteínas. A ß-glucosidase extracelular foi purificada utilizando-se um fracionamento protéico e uma coluna de troca-iônica DEAE-celulose, de onde foram obtidos duas atividades enzimáticas denominadas ß-glucosidases I e II. A ß-glucosidase I foi aplicada em coluna de troca iônica CM-celulose, enquanto que a ß-glucosidase II foi aplicada em Sephadex G-100. A ß-glucosidase I foi purificada 2 vezes com 4.0% de recuperação...

Estudos bioquimico e farmacologico da peçonha de Bothrops erythromelas

Aldete Zappellini
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 27/11/1991 PT
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A B. erythromelas é uma serpente que habita exclusivamente as regiões quentes do Nordeste brasileiro (Bahia ao Ceará). Nesta Tese avaliaram-se características bioquímicas e farmacológicas de sua peçonha. Verificou-se que o veneno apresenta atividades coagulante, proteolítica (caseinolítica), fosfolipásica e hemorrágica, bem como discreta atividade TAME-esterásica. Os fracionamentos realizados revelaram a presença de três (Sephadex G-75) e quatro (Sephadex G-100) picos distintos. No primeiro pico detectaram-se as atividades proteolítica e coagulante, no segundo, TAME-esterásica (ausente em Sephadex G-75), no terceiro, fosfolipásicae coagulante. Nenhuma atividade foi detectada no último pico. Através do estudo farmacológico, verificou-se que a peçonha de B. elyrhromelas é menos tóxica do que a de B. jararaca para camundongos (via intraperitoneal); no entanto, esta relação se inverteu para pintainhos (via, intramuscular). Estudamos também os efeitos deste veneno sobre,a pressão arterial sistêmica e a respiração, bem como sobre o tempo de coagulação, de cães anestesiados. Observou-se que após administração de 25 fJ.g/kg da peçonha (via endovenosa, "bolus"), os animais apresentaram uma queda da pressão arterial que revelou a presença de dois componentes distintos: o primeiro manifestou-se por uma queda de rápida instalação e de moderada intensidadee o segundo...

Produção, purificação e caracterização de enzimas celuloliticas termoestaveis de Humicola sp 179-5 e aplicação destas enzimas

Roberto da Silva
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 18/12/1992 PT
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Uma linhagem de fungo termófilo xilanolítico Humicola sp foi isolada a partir de madeira em decomposição da floresta Amazônica, O fungo produziu quantidade significativa de xilanases termoestáveis quando cultivado a 50ºC em meio de farelo de trigo. A produção de avicelase foi desprezível e de extrato enzimático bruto hidrolsou xilano a 60%, como xilose. Além de atividade de xiIanase o extrato enzimático bruto apresentou atividade de CMCase e de β-glicosidase que foram caracterizadas fisico-quimicamente. A xilanase termoestável a 60°C por 1 hora, foi purificada através de cromatografia em caluna de DEAE-Sephadex A-50 e CM-Sephadex C-50 e revelou três frações de proteínas com atividades xilanásicas, A fração X/1 não se ligou à coluna de DEAE-Sephadex A-50 e foi eluida no volume correspondente ao volume morto da coluna. Os pHs ótimos e temperaturas ótimas das xilanases purificadas foram; 5,0-5,6 e 75°C (X-I); 4,2 e 65ºC (X-II); 5,0-5,6 e 75°C X-III). HgCl2 inibiu completamente as três xilanases, CuSO4.H2O inibiu-as fortemente e MgSO4.7H2O, CoCl2.6H20, FeCl3.6H20 e EDTA acarretaram inibições siqnificativas. CaCl2 estimulou a atividade das três xilanases enquanto iodoacetamida não afetou a atividade destas enzimas. Os pesas moleculares das xilanases X-I e X-II foram 30.000 Da e 43.000 Da...

Purification and chemical characterization of human hexosaminidases A and B.

Lee, J E; Yoshida, A
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/12/1976 EN
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N-Acetyl-beta-hexosaminidases A and B were purified to homogeneity from human placenta. In the initial step of purification, the enzymes were adsorbed on concanavalin A-Sepharose 4B and eluted from the column with alpha-methyl D-mannosides. Subsequent purification steps included DEAE-cellulose column chromatography, QAE-Sephadex [diethyl-(2-hydroxypropyl)aminoethyl-Sephadex] column chromatography, Sephadex G-200 gel filtration and preparative disc polyacrylamide-gel electrophoresis, followed by another QAE-Sephadex chromatography for the hexosaminidase A preparation, and DEAE-cellulose column chromatography, calcium phosphate gel chromatography, Sephadex G-200 gel filtration, QAE-Sephadex chromatography and CM-cellulose chromatography for the hexosaminidase B preparation. The purified preparations, particularly hexosaminidase A, had significantly higher specific enzyme activities than previously reported. The preparations moved on polyacrylamide-gel electrophoresis as single protein bands, which also stained for enzyme activity. Sedimentation-equilibrium centrifugation indicated homogenous dispersion of the enzymes, and the molecular weight was estimated as about 110000 for both enzymes. Complete amino acid and carbohydrate compositions of the two isoenzymes were determined...

Comparison of the substrate specificities of protein phosphatases involved in the regulation of glycogen metabolism in rabbit skeletal muscle.

Antoniw, J F; Nimmo, H G; Yeaman, S J; Cowen, P
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/02/1977 EN
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Muscle extracts were subjected to fractionation with ethanol, chromatography on DEAE-cellulose, precipitation with (NH4)2SO4 and gel filtration on Sephadex G-200. These fractions were assayed for protein phosphatase activities by using the following seven phosphoprotein substrates: phosphorylase a, glycogen synthase b1, glycogen synthase b2, phosphorylase kinase (phosphorylated in either the alpha-subunit or the beta-subunit), histone H1 and histone H2B. Three protein phosphatases with distinctive specificities were resolved by the final gel-filtration step and were termed I, II and III. Protein phosphatase-I, apparent mol.wt. 300000, was an active histone phosphatase, but it accounted for only 10-15% of the glycogen synthase phosphatase-1 and glycogen synthase phosphatase-2 activities and 2-3% of the phosphorylase kinase phosphatase and phosphorylase phosphatase activity recovered from the Sephadex G-200 column. Protein phosphatase-II, apparent mol.wt. 170000, possessed histone phosphatase activity similar to that of protein phosphatase-I. It possessed more than 95% of the activity towards the alpha-subunit of phosphorylase kinase that was recovered from Sephadex G-200. It accounted for 10-15% of the glycogen synthase phosphatase-1 and glycogen synthase phosphatase-2 activity...

The separation of haemagglutination inhibitors from antibodies to parainfluenza viruses by gel filtration on a Sephadex G-200 column

Mekler, L. B.; Pichushkov, A. V.; Zakstelskaya, L. Ja.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /08/1967 EN
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Normal rabbit sera and sera of rabbits hyperimmunized against parainfluenza viruses types I and III were examined. Non-specific inhibitors of parainfluenza haemagglutinin were found in 19S and 4S fractions prepared by gel filtration. Specific antibodies were found in the 7S fraction and these could, therefore, be clearly separated from the non-specific inhibitors by gel filtration on a Sephadex G-200 column.

The isolation of soluble antigen—antibody complexes on Sephadex G-200

Boyns, A. R.; Hardwicke, J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/1966 EN
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1. Soluble antigen—antibody complexes have been isolated on Sephadex G-200 using a rabbit anti-BSA system.

The allergens of Schistosoma mansoni. II. Further separation by sephadex G-200 and ion-exchange chromatography.

Harris, W G
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /11/1975 EN
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A total of thirty-five antigen fractions were prepared from adult Schistosoma mansoni by extraction into borate-buffered saline, precipitation at pH 4-6, gel-filtration on Sephadex G-100 and G-200, and ion-exchange chromatography on CM- and DEAE-cellulose. The allergic activity of these antigens was assayed by a modified Prausnitz-Küstner (P-K) type reaction in rats. The results showed that the allergen-reagin axis in rat schistosomiasis is a multicomponent system involving molecules of widely different chemical nature and molecular weight, rather than a simple, single antigen-antibody interaction. The significance of these findings to the use of purified antigens for the diagnosis of schistosomiasis in the field is discussed.

Flow-cytometric evaluation of lymphocyte subpopulations in synchronously developing Schistosoma mansoni egg and Sephadex bead pulmonary granulomas.

Remick, D. G.; Chensue, S. W.; Hiserodt, J. C.; Higashi, G. I.; Kunkel, S. L.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /05/1988 EN
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Synchronous models of T-cell-mediated and foreign body granulomas were induced in mice by intravenous embolization of Schistosoma mansoni eggs and Sephadex beads, respectively. The authors then performed flow-cytometric analysis of lymphocytes from dispersed granulomas, spleens, and peripheral blood at 4, 8, 16, and 32 days corresponding to the induction, growth, and maintenance, and resolution of these lesions. Lymphocytes were identified on the basis of light scatter characteristics, and the nature of the cells was confirmed by cell sorting and electron-microscopic examination. Lymphocyte subpopulations were characterized with antibodies to lymphocyte surface markers, specifically Ig, Thy 1.2, Lyt 1, Lyt 2, and L3T4. Natural killer cells were identified with anti-asialo GM1. Egg-induced granulomas had more lymphocytes of all phenotypes at all time points. Surprisingly, there was a significant number of cells staining positive for asialo GM1. On Day 16 after embolization there was a greater percentage of helper T cells, as defined by positive staining with L3T4, in the egg model, compared with the bead model. There was no obvious shift of lymphocytes from either the blood or spleen into the granuloma. These data confirm the importance of T cells in the direct participation of granulomatous inflammation...

Fractional Order Analysis of Sephadex Gel Structures: NMR Measurements Reflecting Anomalous Diffusion

Magin, Richard L.; Akpa, Belinda S.; Neuberger, Thomas; Webb, Andrew G.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/12/2011 EN
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We report the appearance of anomalous water diffusion in hydrophilic Sephadex gels observed using pulse field gradient (PFG) nuclear magnetic resonance (NMR). The NMR diffusion data was collected using a Varian 14.1 Tesla imaging system with a home-built RF saddle coil. A fractional order analysis of the data was used to characterize heterogeneity in the gels for the dynamics of water diffusion in this restricted environment. Several recent studies of anomalous diffusion have used the stretched exponential function to model the decay of the NMR signal, i.e., exp[−(bD)α], where D is the apparent diffusion constant, b is determined the experimental conditions (gradient pulse separation, durations and strength), and α is a measure of structural complexity. In this work, we consider a different case where the spatial Laplacian in the Bloch-Torrey equation is generalized to a fractional order model of diffusivity via a complexity parameter, β, a space constant, μ, and a diffusion coefficient, D. This treatment reverts to the classical result for the integer order case. The fractional order decay model was fit to the diffusion-weighted signal attenuation for a range of b-values (0 < b < 4,000 s-mm−2). Throughout this range of b values...

A Hydrogen Exchange Method Using Tritium and Sephadex: Its Application to Ribonuclease*

Englander, S. Walter
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em //1963 EN
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A new method for measuring the hydrogen exchange of macromolecules in solution is described. The method uses tritium to trace the movement of hydrogen, and utilizes Sephadex columns to effect, in about 2 minutes, a separation between tritiated macromolecule and tritiated solvent great enough to allow the measurement of bound tritium. High sensitivity and freedom from artifact is demonstrated and the possible value of the technique for investigation of other kinds of colloid-small molecule interaction is indicated. Competition experiments involving tritium, hydrogen, and deuterium indicate the absence of any equilibrium isotope effect in the ribonuclease-hydrogen isotope system, though a secondary kinetic isotope effect is apparent when ribonuclease is largely deuterated. Ribonuclease shows four clearly distinguishable kinetic classes of exchangeable hydrogens. Evidence is marshaled to suggest the independently measurable classes II, III, and IV (in order of decreasing rate of exchange) to represent “random-chain” peptides, peptides involved in α-helix, and otherwise shielded side-chain and peptide hydrogens, respectively.

Quantitative analysis of polymeric procyanidins (tannins) from grape (Vitis vinifera) seeds by reverse phase high performance liquid chromatography

Peng, Z.; Hayasaka, Y.; Iland, P.; Sefton, M.; Hoj, P.; Waters, E.
Fonte: Amer Chemical Soc Publicador: Amer Chemical Soc
Tipo: Artigo de Revista Científica
Publicado em //2001 EN
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A reverse phase C ₁₈ HPLC method with potential for high automated throughput has been developed for the quantitative analysis of polymeric procyanidins (tannins) in grape seed extracts. Chromatography gave rise to 13 distinct UV-absorbing peaks with good baseline separation. The UV-absorbing peak eluting last is distinct and therefore easily quantified. Biochemical analyses including ultrafiltration, protein precipitation, and Sephadex LH20 chromatography combined with electrospray mass spectrometric analyses establish that this peak predominantly contains polymeric procyanidins. The polymers, which appear to be galloylated to various degrees and seem to fragment in a characteristic manner during electrospray mass spectrometry, are well separated from catechins and procyanidin oligomers of up to 4 units. The recovery of polymeric grape seed tannins with this HPLC method was 86%, which is similar to the 89% recovery achieved with commercial quebracho tannins. The concentration of tannins in seeds from ripe Vitis vinifera cv. Shiraz grapes ranged from 1360 to 2830 mg/kg of berries.

Estimation of serum haemoglobin-binding capacity (haptoglobin) on Sephadex G.100

Ratcliff, A. P.; Hardwicke, J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /11/1964 EN
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A method is described for the estimation of serum haptoglobin as `haemoglobin-binding capacity'. The method relies on column chromatographic separation of the haemoglobin/haptoglobin complex from excess added free haemoglobin on the dextran gel Sephadex G.100. The method is simple and reproducible, and correlates well with another method of estimating haemoglobin-binding capacity over a wide range of values.

Fractionation on Cross-Linked Dextran, Sephadex G-25, of Sera from Sheep Infected with Johne's Bacilli. Preliminary Report

Mori, K. F.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /06/1965 EN
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Ten sera collected during the winter months from six sheep infected with Johne's bacilli were fractionated on Sephadex G-25 columns, and all fractions tested for complement-fixing antibody, anticomplementary properties and for supplementing and inhibitory activities when added to complement-fixation tests of a heterologous antigen-antibody system: bovine or ovine antiserum with Brucella abortus antigen. Serum from a normal sheep was similarly fractionated and examined.

EFFECTS OF CYCLIC AMP AND SEPHADEX FRACTIONS OF CHICK EMBRYO EXTRACT ON CLONED RETINAL PIGMENTED EPITHELIUM IN TISSUE CULTURE

Newsome, D. A.; Fletcher, R. T.; Robison, W. G.; Kenyon, K. R.; Chader, G. J.
Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 01/05/1974 EN
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The effects of dibutyryl cyclic 3',5'-adenosine monophosphate (BcAMP) and Sephadex G-25 fractions of chick embryo extract on the growth rate, morphology, and pigmentation of normal chick retinal pigmented epithelium (PE) were investigated. Seven cloned PE cell lines were each grown in modified Ham's F-12 medium alone (F-12), or in F-12 supplemented with either high molecular weight (H) or low molecular weight (L) fractions of chick embryo extract. Cells grown in F-12 alone or in L medium formed compact epithelial sheets, whereas cells grown in H had a fibrocytic appearance and formed poorly organized monolayers. In H plus BcAMP, cell morphology was more epithelioid than in H alone, and generally the monolayers appeared more differentiated. Under each of these three culture conditions, 2 x 10-4 M BCAMP retarded the increase in cell number and decreased the final number of cells per culture dish, but had little effect on plating efficiency. BcAMP also increased the rate of cell adhesion to a plastic substratum. Pigmentation was marked in cultures grown in F-12 or in L alone, but the addition of BcAMP dramatically reduced visible pigmentation. This effect was reversed when BcAMP was removed from the culture medium. Thus BcAMP modifies cell and colonial morphology...

Preparation of immobilized baker's-yeast glucose 6-phosphate dehydrogenase attached to modified sepharose and sephadex and a comparison of the properties of these preparations with those of the soluble enzyme.

Goheer, M A; Gould, B J; Parke, D V
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/08/1976 EN
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1. Glucose 6-phosphate dehydrogenase (D-glucose 6-phosphate-NADP+ oxidoreductase, EC 1.1.1.49) from baker's yeast (Saccharomyces cerevisiae) was immobilized on CNBr-activated Sepharose 4B with retention of about 3% of enzyme activity. This uncharged preparation was stable for up to 4 months when stored in borate buffer, pH7.6, at 4 degrees C. 2. Stable enzyme preparations with negative or positive overall charge were made by adding valine or ethylenediamine to the CNBr-activated Sepharose 4B 30min after addition of the enzyme. 3. These three immobilized enzyme preparations retained 40-60% of their activity after 15 min at 50 degrees C. The soluble enzyme is inactivated by these conditions. 4. The soluble enzyme lost 45 and 100% of its activity on incubation for 3h at pH6 and 10 respectively. The three immobilized-enzyme preparations were completely stable over this entire pH range. 5. The pH optimum of the positively and negatively charged immobilized-enzyme preparations were about 8 and 9 respectively. The soluble enzyme and the uncharged immobilized enzyme had an optimum pH at about 8.5 6. Glucose 6-phosphate dehydrogenase immobilized on CNBr-activated Sephadex G-25 was unstable, as was enzyme attached to CNBr-activated Sepharose 4B to which glycine...

Proteolytic conversion of insulin-like growth factors to an acidic form(s).

Kuffer, A D; Herington, A C
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/10/1984 EN
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The relative amounts of the various forms of bioassayable insulin-like growth factors (IGF) isolated from human serum or serum fraction Cohn IV-1 depend on the purification procedure. With acid gel filtration or acid/ethanol extraction as the initial step, IGF-II (pI approximately 6.5) was the most abundant (40-70%) followed by somatomedin A (pI approximately 7.4; 15-23%), an acidic form of insulin-like activity (ILA pI 4.8) (13-21%) and IGF-I (pI approximately 8.5; 5-27%). If, however, pH 5.5 ion-exchange chromatography on SP-Sephadex was used prior to acid gel filtration, the acidic pI 4.8 form was the major (greater than 90%) species recovered and was accompanied by a quantitative loss of the other IGF species. This suggested a possible conversion of IGF-I, somatomedin A and/or IGF-II to the acidic ILA pI 4.8 form(s) during the SP-Sephadex procedure. Further experiments indicated that differences in the yields of ILA pI 4.8 were not due simply to differences in the initial pH conditions of the various methods (i.e. acid versus neutral), although exposure to pH 9.7 (a pH experienced during elution of IGF activity from the SP-Sephadex) did appear to play a role. The involvement of the carrier protein in the conversion process was tested by subjecting carrier-free IGF-I and IGF-II to the SP-Sephadex procedure. No conversion of the free forms to ILA pI 4.8 occurred. To examine the possible role of proteinase in the conversion of IGFs to ILA pI 4.8...

The osmotic properties of sulphoethyl-Sephadex. A model for cartilage

Ogston, A. G.; Wells, J. D.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /07/1972 EN
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1. Observations are reported on the variation of the swelling of sulphoethyl-Sephadex C-50 and C-25, and of the partition of NaCl between solution and gel, with the concentration of NaCl. 2. The results were interpreted in terms of Manning's (1969) treatment of the interactions between polyionic polymers and simple electrolytes and of Flory's (1953) treatment of the swelling of gels. 3. The results indicate net inner osmotic pressures as high as 3.6×105Pa (140 mosmolar=3.6×105N/m2) in 0.15m-NaCl. 4. It is suggested that cartilage may have net inner osmotic pressure of the order of 105Pa.

Simultaneous determination of iron and ruthenium by preconcentration on sulfopropyl sephadex cation exchanger

Richter D., Pablo; Paipa Gómez, Carolina; Narváez, Jessica; Toral Ponce, María
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artículo de revista
EN
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A new method for the simultaneous determination of iron and ruthenium at ultra-trace levels is proposed. The method is based on the formation of the iron and ruthenium complexes with 2,4,6-tri-(2-pyridil)-1,3,5-triazine (TPTZ) in the presence of hydroxylamine hydrochloride and buffer CH2ClCOOH/CH2ClCOONa (pH = 3.0). The formation of the complexes and their retention on a cationic resin SP-Sephadex C25 were integrated in one step at 90 degreesC, with stirring for 90 min. Under these conditions a high preconcentration level was achieved for both analytes. The complexes retained on the solid phase were evaluated by second derivative spectrophotometry. The selected analytical wavelengths were 539.7 and 553.3 nm for the determination of ruthenium and iron, respectively, by using the zero crossing approach. The detection and quantification limits were 0.54 ng ml(-1) and 1.79 ng ml(-1) for ruthenium and 0.41 ng ml(-1) and 1.38 ng ml(-1) for iron. The proposed method was applied to the determination of both analytes in synthetic mixtures.

Solid phase spectrophotometric determination of copper in water by using immobilized zincon in a Sephadex A25 resin

Castro, H.; Toral Ponce, María; Richter D., Pablo
Fonte: MARCEL DEKKER INC Publicador: MARCEL DEKKER INC
Tipo: Artículo de revista
EN
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A new simple, sensitive and selective solid phase spectrophotometric method has been developed for determination of copper in water. A sensitive analytical zone was prepared by immobilization of zincon in a Sephadex A25 resin, in which copper reacts selectively, at pH 7, to form a colored complex on the surface of the resin. Absorbances can be read directly on the solid phase at 621.5 mn. The batch mode was adopted in this work, because the resin is not reusable due the reaction product that is retained irreversible on it. Physico-chemical variables of the method were optimized in order to find the best analytical conditions for the determination. Under the selected conditions copper can be accurately determined oil the range 0.4-300 ng/mL, with a detection limit of 0.12 ng/mL and a repeatability, expressed as the relative standard deviation, lower than 3.8%. The recovery in the analysis of a certified reference material was 100.4%. By changing the pH of the sample, other metals also react (Fe, Cd, Ni, Zn, Hg. Pb), indicating that this system also can be used for screening to determine the possible presence of other trace metals in waters.