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Simultaneous flow injection preconcentration of lead and cadmium using cloud point extraction and determination by atomic absorption spectrometry

SILVA, Edson Luiz; ROLDAN, Paulo dos Santos
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.55%
A flow injection (FI) micelle-mediated separation/preconcentration procedure for the determination of lead and cadmium by flame atomic absorption spectrometry (FAAS) has been proposed. The analytes reacted with 1-(2-thiazolylazo)-2-naphthol (TAN) to form hydrophobic chelates, which were extracted into the micelles of 0.05% (w/v) Triton X-114 in a solution buffered at pH 8.4. In the preconcentration stage, the micellar solution was continuously injected into a flow system with four mini-columns packed with cotton, glass wool. or TNT compresses for phase separation. The analytes-containing micelles were eluted from the mini-columns by a stream of 3 mol L(-1) HCl solution and the analytes were determined by FAAS. Chemical and flow variables affecting the preconcentration of the analytes were studied. For 15 mL. of preconcentrated solution, the enhancement factors varied between 15.1 and 20.3, the limits of detection were approximately 4.5 and 0.75 mu g L(-1) for lead and cadmium, respectively. For a solution containing 100 and 10 mu g L(-1) of lead and cadmium, respectively, the R.S.D. values varied from 1.6 to 3.2% (n = 7). The accuracy of the preconcentration system was evaluated by recovery measurements on spiked water samples. The method was susceptible to matrix effects...

Peat as a natural solid-phase for copper preconcentration and determination in a multicommuted flow system coupled to flame atomic absorption spectrometry

GONZALES, A. P. S.; FIRMINO, M. A.; NOMURA, C. S.; ROCHA, F. R. P.; OLIVEIRA, P. V.; GAUBEUR, I.
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.3%
The physical and chemical characteristics of peat were assessed through measurement of pH, percentage of organic matter, cationic exchange capacity (CEC), elemental analysis, infrared spectroscopy and quantitative analysis of metals by ICP OES. Despite the material showed to be very acid in view of the percentage of organic matter, its CEC was significant, showing potential for retention of metal ions. This characteristic was exploited by coupling a peat mini-column to a flow system based on the multicommutation approach for the in-line copper concentration prior to flame atomic absorption spectrometric determination. Cu(II) ions were adsorbed at pH 4.5 and eluted with 0.50 mol L(-1) HNO(3). The influence of chemical and hydrodynamic parameters, such as sample pH, buffer concentration, eluent type and concentration, sample flow-rate and preconcentration time were investigated. Under the optimized conditions, a linear response was observed between 16 and 100 mu g L(-1), with a detection limit estimated as 3 mu g L(-1) at the 99.7% confidence level and an enrichment factor of 16. The relative standard deviation was estimated as 3.3% (n = 20). The mini-column was used for at least 100 sampling cycles without significant variation in the analytical response. Recoveries from copper spiked to lake water or groundwater as well as concentrates used in hemodialysis were in the 97.3-111 % range. The results obtained for copper determination in these samples agreed with those achieved by graphite furnace atomic absorption spectrometry (GFAAS) at the 95% confidence level. (C) 2009 Elsevier B.V. All rights reserved.; Brazilian agencies Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP); Fundo Mackenzie de Pesquisa and Universidade Federal do ABC (UFABC); Fundo Mackenzie de Pesquisa and Universidade Federal do ABC (UFABC)

Determinação de íons metálicos por FI-FAAS após separação e concentração em fase sólida: avaliação crítica de adsorventes; Determination of metallic ions by FI-FAAS after separation and preconcentration in solid-phase: critical evaluation of adsorbents

Anaia, Grazielle de Campos
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 29/02/2008 PT
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37.3%
Um procedimento de separação e pré-concentração em sistemas de análises em fluxo acoplado a espectrometria de absorção atômica com atomização em chama (FI-FAAS) é proposto para a determinação de Cu(II), Ni(II) e Cd(II). Diferentes adsorventes (XAD-7, sílica-gel e sílica funcionalizada C18) foram avaliados para a imobilização do reagente 1-(2-tiazolilazo)-2-naftol (TAN) que forma complexos com diversos íons metálicos. A avaliação e seleção do adsorvente baseou-se em isotermas de adsorção (Langmuir, Freundlich e Dubinin- Radushkevich (D-R)) e estudos de dessorção. O modelo de Langmuir indicou que a -2 -1 sílica-gel adsorve uma quantidade maior de TAN (1,81±0,08)x10-2 g g-1 em relação à XAD-7 (4,05±0,51)x10-3 g g-1 e à sílica funcionalizada C18 1,58x10-2 g g-1 . Pelo modelo de Freundlich, foi verificado que a superfície da XAD-7 apresenta elevada heterogeneidade energética dos sítios de adsorção evidenciado pelo parâmetro n de 2,57±0,08 contra 1,01±0,02 para sílica-gel. A constante de Freundlich foi de -1 (0,232±0,023) e (2,27±0,59) g g-1 para XAD-7 e sílica-gel, respectivamente. O modelo de D-R revelou que ocorre fisissorção para ambos os adsorventes. Estudos de dessorção permitiram concluir que a XAD-7 modificada apresentou a menor massa de TAN dessorvida em comparação com a sílica-gel...

Desenvolvimento de estratégias de pré-concentração para eletroforese capilar (CE) visando a análise de pesticidas em frutas e leguminosas; Development of preconcentration strategies for pesticides analysis by capillary electrophoresis (CE) in fruits and tubers

Silva, Clóvis Lúcio da
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 30/04/2003 PT
Relevância na Pesquisa
37.41%
O uso de pesticidas constitui um importante aspecto na agricultura moderna, com inquestionável beneficio na produção agrícola. Porém a contaminação dos alimentos por pesticidas constitui um sério risco a saúde do consumidor. A determinação de resíduo de pesticidas em alimentos envolve procedimentos laboriosos, com elevado tempo de análise e várias etapas de pré-concentração. Neste trabalho, procedimentos alternativos de extração e pré-concentração para analise multiresíduo de pesticida em água, frutas e tubérculos foram desenvolvidos. A eletroforese capilar em seu modo MEKC em condições de alto e baixo fluxo eletrosmótico foi empregado para a otimização da separação de diferentes classes de pesticidas (triazinas, organofosforado, carbendamidazóis, feniluréia e carbamatos). A composição do eletrólito de separação otimizada para condições de alto EOF foi: 10 mmol L-1 de tetraborato de sódio (pH 9,3),50 mmol L-1 de SDS e 5% etanol e 5% propanol, enquanto que para condições de baixo EOF foi: 10 mmol L-1 de tampão fosfato (pH 2,5), 25 mmol L-1 de SDS e 10% metanol. Estratégias de pré-concetração on-line conhecida como sweeping (SW) e stacking nos modos de migração reversa das micelas (SRMM) e migração reversa com um plug de água (SWR) bem como as suas versões modificadas foram avaliadas...

Preconcentration and determination of Cu(II) in a fresh water sample using modified silica gel as a solid-phase extraction adsorbent

Pereira, A. S.; Ferreira, G.; Caetano, L.; Martines, M. A. U.; Padilha, P. M.; Santos, A.; Castro, G. R.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 399-403
ENG
Relevância na Pesquisa
37.3%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Processo FAPESP: 06/54946-9; A method was developed to attach 4-amino-2-mercaptopyrimidine (AMP) onto silica gel surface and to determine trace metals. The Surface functionalization reaction was performed with a silylant agent, chloropropyltrimethoxysilane (Si-CPTS), and the product, Si-AMP, was characterized by FT-IR and elemental analysis to evaluate the Surface modification. The functionalized silica was applied in the sorption of Cu(II) ions from an aqueous medium. The series of adsorption isotherms were adjusted to a modified Langmuir equation and the maximum number of moles of adsorbed copper was 0.447 mmol g(-1). The modified material was placed in a preconcentration system, where it reached ail approximately 20-fold enrichment factor using 5 mg of Si-AMP. The proposed method was applied in the preconcentration and determination of Cu(II) in a fresh water sample from the Parana river and was validated through a comparative analysis of a standard reference material (1643 e). (C) 2009 Elsevier B.V. All rights reserved.

Flame AAS determination of metal ions in fuel ethanol after preconcentration on acid carboxymethylcellulose (CMCH)

Padilha, P. M.; Padilha, CCF; Rocha, J. C.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 299-303
ENG
Relevância na Pesquisa
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This paper describes the preparation of acid carboxymethylcellulose (CMCH), and the results of a study on the adsorption and preconcentration (using batch and flow-through column methods) of Cd(II), Cu(II), Cr(III), Fe(III), Ni(II) and Zn(II) in ethanol medium. The adsorption capacities for each metallic ion were (in mmol g(-1)) Cd(II) = 0.92; Cu(II) = 1.45; Cr(III) = 1.70; Fe(III) = 1.60; Ni(II) = 1.30; and Zn(II) = 1.10. By means of the flow-through method, a recovery of ca. 100% of the metallic ions adsorbed in a column packed with 2 g of CMCH was found when 5.0 mL of 1.0 mol L-1 hydrochloric acid were used as eluent. An enrichment factor of 20 (100 mt solution containing 50 mu g L-1 of the metallic ions, concentrated to 5.0 mt) was obtained by this preconcentration procedure. The sorption-desorption procedure applied allowed the development of a preconcentration and Flame AAS quantification method of metallic ions in fuel ethanol at trace levels.

Determination of copper, iron, nickel and zinc in gasoline by FAAS after sorption and preconcentration on silica modified with 2-aminotiazole groups

Roldan, P. S.; Alcantara, I. L.; Padilha, CCF; Padilha, P. M.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 305-309
ENG
Relevância na Pesquisa
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Silica gel chemically modified with 2-aminotiazole groups (SiAT), was used for preconcentration of cupper, zinc, nickel and iron from gasoline, normally used as a engine fuel. Surface characteristics and surface area of the silica gel were obtained before and after chemical modification using FT-IR, Kjeldhal and surface area analysis (B.E.T.). The retention and recovery of the analyte elements were studied by applying batch and column techniques. The experimental parameters, such as shaking time in batch technique, flow rate and concentration of the eluent (HCl-0.25-2.00 mol 1(-1)) and the amount of silica, on retention and elution, have been investigated. Detection limits of the method for cupper, iron, nickel and zinc are 0.8, 3, 2 and 0.1 mug 1(-1), respectively. The sorption-desorption of the studied metal ions made possible the development of a preconcentration method for metal ions at trace level in gasoline using flame AAS for their quantification. (C) 2004 Published by Elsevier Ltd.

The use of silica-immobilized brown alga (Pilayella littoralis) for metal preconcentration and determination by inductively coupled plasma optical emission spectrometry

Carrilho, ENVM; Nobrega, J. A.; Gilbert, T. R.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 1131-1140
ENG
Relevância na Pesquisa
37.3%
The brown alga Pilayella littoralis was used as a new biosorbent in an on-line metal preconcentration procedure in a flow-injection system. Al, Co, Cu and Fe were determined in lake water samples by inductively coupled plasma optical emission spectrometry (ICP-OES) after preconcentration in a silica-immobilized alga column. Like other algae, P. littoralis exhibited strong affinity for these metals proving to be an effective accumulation medium. Metals were bound at pH 5.5 and were displaced at pH < 2 with diluted HCl. The enrichment factors for Cu-II, Fe-III, Al-III and Co-II were 13, 7, 16 and 11, respectively. Metal sorption efficiency ranged from 86 to 90%. The method accuracy was assessed by using drinking water certified reference material and graphite furnace atomic absorption spectrometry (GFAAS) as a comparison technique. The column procedure allowed a less time consuming, easy regeneration of the biomaterial and rigidity of the alga provided by its immobilization on silica gel. (C) 2003 Elsevier B.V. All rights reserved.

Preconcentration of heavy metals ions from aqueous solutions by means of cellulose phosphate: An application in water analysis

De Magalhães Padilha, P.; Rocha, J. Cesar; Moreira, J. Celso; De Sousa Campos, J. Theodoro; Do Carmo Federici, C.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 317-323
ENG
Relevância na Pesquisa
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Cellulose phosphate (CELLPHOS) was studied as a collector for analytical preconcentration of traces of Cd(II), Cr(III), Cu(II) and Ni(II) from aqueous sample solution. It has been proved that using chromatographic columns packed with CELLPHOS for preconcentration and 1.0 mol 1 -1 HCl for elution the adsorbed analytes are quantitatively enriched. An enrichment factor of 20 (100 ml sample, 5 ml concentrate) was achieved by this separation procedure, which was applied to a series of water analyses (river, sea, bog water).

Determination of metal ions in fuel ethanol after preconcentration on 5-amino-1,3,4-thiadiazole-2-thiol modified silica gel

Gomes, Luis A. de Melo; Padilha, Pedro de Magalhães; Moreira, José Celso; Dias Filho, Newton L.; Gushikem, Yoshitaka
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 494-498
ENG
Relevância na Pesquisa
37.3%
This work describes the synthesis and characterization of 5-amino-1,3,4-thiadiazole-2-thiol modified silica gel (SiATT), and the results of a study of the adsorption and preconcentration (in batch, and in flow using a column technique) of Cd(II), Co(II), Cu(II), Fe(III), Ni(II), Pb(II) and Zn(II) in ethanol medium. The adsorption capacities for each metal ion were (in mmol g -1): Cd(II) = 0.11, Co(II) = 0.10, Cu(II) = 0.20, Fe(III) = 0.20, Ni(II) = 0.16, Pb(II) = 0.08 and Zn(II) = 0.12. The results obtained in the flow experiments, showed a recovery of ca. 100% of the metal ions adsorbed in a column packed with 2 g of SiATT, using 5 mL of 2.0 mol L -1 HCl solution as eluent. The sorption-desorption of the metal ions made possible the development of a preconcentration method and quantification by Flame AAS of metal ions at trace level in fuel ethanol.

Determination of vanadium in urine by electrothermal atomic absorption spectrometry using hot injection and preconcentration into the graphite tube

Fernandes, Kelly G.; Nogueira, Ana Rita A.; Gomes Neto, José A.; Nóbrega, Joaquim A.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 676-681
ENG
Relevância na Pesquisa
37.41%
In this work it was developed a procedure for the determination of vanadium in urine samples by electrothermal atomic absorption spectrometry using successive injections for preconcentration into a preheated graphite tube. Three 60 μL volumes were sequentially injected into the atomizer preheated to a temperature of 110°C. Drying and pyrolysis steps were carried out after each injection. A chemical modifier, barium difluoride (100 mg L-1), and a surfactant, Triton X-100 (0.3% v v-1), were added to the urine sample. When injecting into a hot graphite tube, the sample flow-rate was 0.5 μL s-1. The limits of detection and quantification were 0.54 and 1.82 without preconcentration, and 0.11 and 0.37 μg L-1 with preconcentration, respectively. The accuracy of the procedure was evaluated by an addition-recovery experiment employing urine samples. Recoveries varied from 96.0 to 103% for additions ranging from 0.8 to 3.5 μg L-1 V. The developed procedure allows the determination of vanadium in urine without any sample pretreatment and with minimal dilution of the sample.

Pré-concentração baseada na técnica de ring oven para microanálise : determinação simultânea de sódio, ferro e cobre em etanol hidratado combustível por espectroscopia de emissão óptica em plasma induzido por laser (LIBS); Preconcentration based on ring oven technique for micro-analysis : simultaneous determination of sodium, iron and copper in fuel ethanol by laser induced breakdown spectroscopy (LIBS)

Juliana Cortez
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 31/10/2012 PT
Relevância na Pesquisa
37.41%
A técnica de ring oven, originalmente desenvolvida por Weisz em 1954 e revisitada com o objetivo de ser utilizada em um procedimento simples e altamente eficiente de pré-concentração de analitos antes da determinação por técnicas analíticas de microanálise. A técnica de pré-concentração proposta e baseada na utilização de um pequeno volume de amostra que e transferida gota-a-gota, com o auxílio de um sistema de análise por injeção em fluxo, para um substrato de papel de filtro. O papel de filtro e mantido em um pequeno forno circular aquecido (ring oven). As gotas da solução da amostra difundem por capilaridade do centro do papel de filtro para a frente do solvente. Depois do término do processo, um anel com um contorno circular bem definido (0,35 mm de largura e cerca de 2,0 cm de diâmetro) e formado no papel de filtro e este contém, pré-concentrados, os elementos presentes no volume processado de amostra. Coeficientes de preconcentração do analito podem alcancar 250 vezes (m/ m) para um volume de amostra de 600 mL. O sistema proposto foi avaliado para pré-concentrar Na, Fe e Cu presentes em amostras de etanol hidratado combustível, em nível de mg mL. O procedimento de pré-concentração não utiliza nenhum solvente adicional...

Determination of aluminum in food samples after preconcentration as aluminon complex on microcrystalline naphthalene by spectrophotometry

Fathi,Mohammad Reza; Pourreza,Nahid; Ardan,Zeinab
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2011 EN
Relevância na Pesquisa
37.3%
A sensitive preconcentration procedure for spectrophotometeric determination of aluminum was developed. Aluminum as aluminon complex is adsorbed on microcrystalline naphthalene. The naphthalene containing the complex is dissolved in 3 mL of acetone and its absorbance is measured at 544 nm. The effect of various factors on the preconcentration of aluminum was investigated. The calibration graph was linear in the range of 1-60 mg L-1. The limit of detection was 0.52 mg L-1 and relative standard deviation for the determination of 5 mg L-1 was 2.65%. The proposed solid phase extraction procedure was applied to determination of aluminum in food samples.

Use of experimental design in the optimisation of a solid phase preconcentration system for Cobalt determination by GFAAS

Matos,G. D.; Tarley,C. R. T.; Ferreira,S. L. C.; Arruda,M. A. Z.
Fonte: Fundação Editora da Universidade Estadual Paulista Júlio de Mesquita Filho - UNESP Publicador: Fundação Editora da Universidade Estadual Paulista Júlio de Mesquita Filho - UNESP
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2005 EN
Relevância na Pesquisa
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In this work is proposed a solid phase preconcentration system of Co2+ ions and its posterior determination by GFAAS in which fractional factorial design and response surface methodology (RSM) were used for optimization of the variables associated with preconcentration system performance. The method is based on cobalt extraction as a complex Co2+-PAN (1:2) in a mini-column of polyurethane foam (PUF) impregnated with 1-(2-pyridylazo)-naphthol (PAN) followed by elution with HCl solution and its determination by GFAAS. The chemical and flow variables studied were pH, buffer concentration, eluent concentration and preconcentration and elution flow rates. Results obtained from fractional factorial design 2(5-1) showed that only the variables pH, buffer concentration and interaction (pH X buffer concentration) based on analysis of variance (ANOVA) were statistically significant at 95% confidence level. Under optimised conditions, the method provided an enrichment factor of 11.6 fold with limit of detection and quantification of 38 and 130 ng L-1, respectively, and linear range varying from 0.13 to 10 µg L-1. The precision (n = 9) assessed by relative standard deviation (RSD) was respectively 5.18 and 2.87% for 0.3 and 3.0 µg L-1 cobalt concentrations.

Copper, zinc and manganese determination in saline samples employing faas after separation and preconcentration on Amberlite XAD-7 and Dowex 1x-8 loaded with Alizarin Red S

Korn,Maria das Graças A.; Santos Jr.,Aníbal de Freitas; Jaeger,Helena V.; Silva,Nívia Maria S.; Costa,Antônio C. Spínola
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2004 EN
Relevância na Pesquisa
37.49%
Two procedures have been proposed and compared for separation and preconcentration of trace amounts of manganese, copper, and zinc in saline samples. The procedures are based in the use of Amberlite XAD-7 and an anion-exchanger Dowex 1X8-50 loaded with Alizarin Red S (ARS). In order to obtain quantitative recoveries of metal ions, various experimental parameters such as pH, shaking time, sample volume, amounts of solid phase, effects of concomitants, capacity and cations desorptions from solid phases were optimized. For Amberlite XAD-7 impregnated with ARS (XAD 7-ARS), Mn, Cu, and Zn were quantitatively retained, in the pH range 8.5-10.0, by using 0.50 g of solid phase, stirring time of 5 min and a total mass up to 200 µg of each cation. The sorbed elements were subsequently eluted with 5 mL of 3 mol L-1 HNO3, with recovering over 95%, and a fifty-fold preconcentration factor for Zn and a ten-fold preconcentration factor for Mn and Cu were obtained. For Dowex 1X8-50 impregnated with ARS (Dowex-ARS), Cu and Mn were quantitatively retained in the pH range 8.1 to 9.0, and Zn pH 8.1, by using 0.75 g of solid phase, 90 min of stirring time and a total mass up to 50 µg of each cation. The sorbed elements were subsequently eluted with 20 mL of 2 mol L-1 HNO3...

Determination of vanadium in urine by electrothermal atomic absorption spectrometry using hot injection and preconcentration into the graphite tube

Fernandes,Kelly G.; Nogueira,Ana Rita A.; Gomes Neto,José A.; Nóbrega,Joaquim A.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2004 EN
Relevância na Pesquisa
37.41%
In this work it was developed a procedure for the determination of vanadium in urine samples by electrothermal atomic absorption spectrometry using successive injections for preconcentration into a preheated graphite tube. Three 60 µL volumes were sequentially injected into the atomizer preheated to a temperature of 110 ºC. Drying and pyrolysis steps were carried out after each injection. A chemical modifier, barium difluoride (100 mg L-1), and a surfactant, Triton X-100 (0.3% v v-1), were added to the urine sample. When injecting into a hot graphite tube, the sample flow-rate was 0.5 µL s-1. The limits of detection and quantification were 0.54 and 1.82 without preconcentration, and 0.11 and 0.37 µg L-1 with preconcentration, respectively. The accuracy of the procedure was evaluated by an addition-recovery experiment employing urine samples. Recoveries varied from 96.0 to 103% for additions ranging from 0.8 to 3.5 µg L-1 V. The developed procedure allows the determination of vanadium in urine without any sample pretreatment and with minimal dilution of the sample.

Immobilized stearic acid as a new sorbent for on-line preconcentration and determination of lead by flow injection flame atomic absorption spectrometry

Dadfarnia,Shayessteh; Shabani,Ali Mohammed Haji; Dehghani,Zahra
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2006 EN
Relevância na Pesquisa
37.49%
The present study examines the possibility of immobilization of stearic acid on microcrystalline naphthalene for preparation of microcolumn and evaluation of its potential for adsorption and preconcentration of trace amounts of metal ions. It was found that this sorbent has high affinity for lead. Consequently, a rapid on-line preconcentration technique for the determination of lead by Flow Injection Flame Atomic Absorption Spectrometry had been devised. Preconcentration was based on accumulation of analyte on immobilized stearic acid microcolumn and subsequent elution by injection of a small volume of nitric acid (250 µL of 1 mol L-1). A sample volume of 20 mL resulted in a preconcentration factor of 84, and relative standard deviations for solutions containing 40 and 200 µg L-1 were 5.1 and 1.2%, respectively. The procedure was applied to tap water, river water, sea water, apple juice, beet leaf, urine, and certified stainless steel. The accuracy was proved by performing recovery experiments, Graphite Furnace Atomic Absorption Spectrometry measurements, and analysis of a stainless steel certified reference material.

Synthesis and application of a functionalized polystyrene resin for on-line preconcentration and determination of cobalt(II) in water samples by flow injection/FAAS

Chamjangali,Mansour Arab; Sharif-Razavian,Laleh; Bahramian,Bahram; Bagherian,Ghadamali
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2010 EN
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A simple and sensitive flow injection-flame atomic absorption spectrometric (FI-FAAS) method was developed for on-line preconcentration and determination of trace levels of cobalt(II). A mini-column packed with a chloromethylated polystyrene, functionalized with N,N-bis(naphthylideneimino)diethylenetriamine (PS-NAPdien) was used for on-line enrichment of cobalt(II) from samples at pH 7.0. All chemical and flow variables were optimized. Under the optimum conditions, calibration graph was linear over the concentration ranges of 1.0-80.0 and 0.30-40.0 µg L-1 for preconcentration of 10.0 and 20.0 mL solutions, respectively. The limits of detection (LODs) values for preconcentration of 10.0 and 20.0 mL sample solutions were 0.75 and 0.25 µg L-1, respectively. An enrichment factor of 110 for a sample volume of 10.0 mL was obtained. The relative standard deviations for 10 replicate determinations of cobalt(II) at the 10.0 and 60.0 µg L-1 levels were 4.7 and 3.3%, respectively. The accuracy of the proposed method was demonstrated by determining Co(II) in different spiked water samples.

Application of simplex optimization in the development of an automated online preconcentration system for manganese determination

Santos,Queila O. dos; Novaes,Cléber G.; Bezerra,Marcos A.; Lemos,Valfredo A.; Moreno,Islania; Silva,Douglas G. da; Santos,Leandro dos
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2010 EN
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37.41%
An automated procedure was developed to determine trace amounts of manganese from vegetal leaves and river waters using flame atomic absorption spectrometry (FAAS) after online preconcentration of this metal using an Amberlite XAD-4 minicolumn modified with 2-aminothiophenol. The preconcentration system is based on the solid-phase extraction of the metal into the minicolumn and elution with 0.30 mol L-1 hydrochloric acid, followed by its determination. Variables associated with the preconcentration system performance, such as pH, sampling flow rate and eluent concentration were optimized using a basic simplex as multivariate technique. The developed method provides an improvement factor of 14 along with limit of detection (3σB) of 2.0 µg L-1, and precision expressed as a 2.2% relative standard deviation (RSD%, n = 10, 30.0 µg L-1). The procedure was applied to determine manganese in river waters collected from urban area of Jequié/Bahia. The accuracy of the procedure was checked by analysis of two certified reference materials (apple leaves, NIST 1515 and spinach leaves, NIST 1570). The developed procedure has been applied for manganese determination in vegetal leaves (chive, spinach, cauliflower and cabbage).

Desenvolvimento de metodologia analítica para extração e pré-concentração de Ag(I) utilizando a moringa oleifera Lam.; Development of analytical methodology for extraction and preconcentration of Ag(I) using the Moringa oleifera Lam.

Araújo, Cleide Sandra Tavares
Fonte: Universidade Federal de Uberlândia Publicador: Universidade Federal de Uberlândia
Tipo: Tese de Doutorado
POR
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Processos industriais tem sido historicamente um importante fator de degradação ambiental. A disposição inadequada de resíduos industriais contendo metais tóxicos em fontes de águas representa um grande problema, que concerne não somente à biota, mas também para humanos. Neste trabalho, foi avaliada a capacidade adsortiva das sementes trituradas de Moringa oleifera Lam. como um material alternativo para remoção e pré-concentração de íons Ag(I) em águas. No primeiro capítulo foi avaliada a capacidade das sementes de moringa para remoção de íons Ag(I) em sistemas aquosos contaminados por este íon metálico. Antes da otimização dos parâmetros foram realizados testes preliminares com a moringa envolvendo a casca da semente, polpa da semente e a semente integral para avaliar a parte da semente que apresentava maior capacidade de remoção, e como espécie analítica de interesse, utilizou-se íons Ag(I). Os resultados mostram maior eficiência usando as sementes integrais. Os parâmetros de otimização avaliados para o adsorvente nos ensaios de remoção foram: granulometria, pH e tempo de agitação, volume de solução, concentração e massa do adsorvente. A quantificação do teor de prata, antes e após o tratamento...