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Construção e avaliação de eletrodos de membrana sólida cristalina seletivos a cobre e prata; Construction and evolution copperand silver ion selective electrode based on crystalline solid membranes

Serrano, Silvia Helena Pires
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 12/02/1988 PT
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O presente trabalho visou a construção e avaliação de eletrodos de membrana sólida cristalina seletivos a cobre e prata. Obteve-se o sulfeto de prata, material eletroativo usado na preparação de membranas seletivas a íons Ag+, por precipitação com gás sulfídrico em meio ácido. Eletrodos com membranas de 1,0 e 0,50 mm de espessura apresentaram respectivamente limites nernstianos de 10-4 e 10-5 Mol.L-1 e precisão de ± 0,1 e 1 mV nas leituras de potencial. Os sulfetos de cobre e prata, usados na preparação de membranas seletivas para determinação de cobre, foram obtidos por precipitação simultânea com gás sulfídrico, tioacetamida em meio ácido e tiouréia em meio amoniacal. Difratogramas de Raios X revelaram que o material obtido com tiouréia corresponde ao sulfeto ternário, Cu2S.3Ag2S ou Ag1,55Cu0,45S, responsável pela resposta seletiva do sensor em soluções de Cu2+. O eletrodo construído a partir deste sulfeto, onde o cobre aparece no estado monovalente, apresentou limite nernstiano da ordem de10-7Mol.L-1, fornecendo resultados satisfatórios na determinação deste metal em amostras de aguardente e álcool. Cálculos termodinâmicos mostraram que quando membrana é constituída de CuS, um contacto elétrico efetuado através de cobre ou prata é instável...

Tangential-flow ultrafiltration: a versatile methodology for determination of complexation parameters in refractory organic matter from Brazilian water and soil samples

Romao, LPC; Castro, G. R.; Rosa, A. H.; Rocha, J. C.; Padilha, P. M.; Silva, H. C.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica Formato: 1097-1100
ENG
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In this work the copper(II) complexation parameters of aquatic organic matter, aquatic and soil humic substances from Brazilian were determined using a new versatile approach based on a single-stage tangential-flow ultrafiltration (TF-UF) technique (cut-off 1 kDa) and sensitive atomic spectrometry methods. The results regarding the copper(II) complexation capacity and conditional stability constants obtained for humic materials were compared with those obtained using direct potentiometry with a copper-ion-selective electrode. The analytical procedure based on ultrafiltration is a good alternative to determine the complexation parameters in natural organic material from aquatic and soil systems. This approach presents additional advantages such as better sensibility, applicability for multi-element capability, and its possible to be used under natural conditions when compared with the traditional ion-selective electrode.

Construction and use of a tubular picrate ion-selective electrode for reducing sugar determination in Port wine by flow-injection analysis

Lopes, Teresa I. M. S.; Rangel, António O. S. S.; Lima, José L. F. C.; Montenegro, M. Conceição B. S. M.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //1995 ENG
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A picrate ion-selective electrode without inner reference solution and based on bis(triphenylphosphoranylidene)ammonium picrate dissolved in 2-nitrophenyloctyl ether was constructed and its characteristics assessed. With respect to reducing sugar determination in Port wine, a tubular electrode based on the same sensor system was developed and incorporated into a flow-injection manifold devised for this determination. The methodology involves a reaction between the reducing sugar and picric acid, the decrease in the picrate concentration being monitored with the tubular electrode. A linear dependence between peak width, at a fixed potential and the logarithm of sugar concentration in the range 25–200 g l−1 was obtained. The proposed system allows wine samples to be injected with no previous treatment and allows a sample throughput of 50 determinations per hour, a relative standard deviation less than 4%, and the results are comparable to the reference procedures.

Potentiometric determination of total nitrogen in soils by flow injection analysis with a gas-diffusion unit

Ferreira, Alexandra M. R.; Lima, José L. F. C.; Rangel, António O. S. S.
Fonte: CSIRO Publishing Publicador: CSIRO Publishing
Tipo: Artigo de Revista Científica
Publicado em //1996 ENG
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A flow injection analysis (FIA) system incorporating a gas-diffusion unit and a potentiometric detector was developed for the determination of total nitrogen in soil digests. The solutions obtained from the Kjeldahl digestion of the soil samples were injected in the FIA system where ammonium was converted into ammonia. This gas diffused through a gas-permeable membrane to a buffer acceptor stream, allowing the separation of the gas from the rest of the sample. Once in contact with the buffer solution, ammonia was reconverted into ammonium and finally led to a tubular ammonium ion-selective electrode constructed for this purpose. The potentiometric detector is a PVC tubular selective electrode without inner reference solution, and with the sensor system composed of monactin in Tris (2-ethylhexyl) phosphate. Good agreement was obtained between the results provided with the developed FIA system and those from the classical Kjeldahl distillation/titration step, with relative deviations between the 2 methods always < 5%. A sampling rate of 80 determinations/h was achieved with good reproducibility for consecutive injections of soil digests (coefficients of variation < 3%).

Sistema automático para determinação seqüencial de cianeto livre e total empregando eletrodo tubular íon-seletivo de membrana homogênea

Marin,Maria Angélica Bonadiman; Silva,Reinaldo Carvalho da; Lehmkuhl,Arilson; Silva,José Bento Borba da; Ganzarolli,Edgard Moreira; Queiróz,Roldão Roosevelt Urzêdo de
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2000 PT
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This study presents an automated system for potentiometric determination of free and total cyanide which employs a homogeneous membrane tubular ion-selective electrode. After the electrode is assembled, it is connected to a system composed of 3 three-way solenoid valves, sample line, carrier line, acid stream, and gas diffusion chamber. A Turbo Pascal® computer program, developed specifically for this task, automatically performs all the steps involved in data acquisition and processing. The proposed analytical procedure offers operational simplicity, since detection is performed by a tubular electrode, whose assembly is fast and easy. The system has shown reproducibility (r.s.d. < 0.5%, n=6) and high speed (30 readings/hour); it is efficient for determination of free and total cyanide in waste waters of starch processing plants. The detection limit was 1.2x10-5 and 1.5x10-5 mol L-1, for determination of free and total cyanide, respectively. The linear response range was between 1.2x10-5 and 1.0x10-2 mol L-1 for free cyanide and between 1.5x10-5 and 1.0x10-2 for total cyanide.

Eletrodo íon-seletivo para determinação potenciométrica de alumínio(III) em meio de fluoreto

Piccin,Evandro; Fatibello-Filho,Orlando; Ramos,Luiz Antonio
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2004 PT
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The construction and analytical evaluation of a coated graphite Al(III) ion-selective electrode, based on the ionic pair formed between the Al(F)n3-n anion and tricaprylylmethylammonium cation (Aliquat 336S) incorporated on a poly(vinylchloride) (PVC) matrix membrane are described. A thin membrane film of this ionic pair and dibutylphthalate (DBPh) in PVC was deposited directly on a cylindric graphite rod (2 cm length x 0.5 cm diameter) attached to the end of a glass tube using epoxy resin. The membrane solution was prepared by dissolving 40% (m/m) of PVC in 10 mL of tetrahydrofuran following addition of 45% (m/m) of DBPh and 15% (m/m) of the ionic pair. The effect of membrane composition, fluoride concentration, and several concomitants as potential interferences on the electrode response were investigated. The aluminium(III) ion-selective electrode showed a linear response ranging from 1.4 x 10-4 to 1.0 x 10-2 mol L-1, a detection limit of 4.0 x 10-5 mol L-1, aslope of -54.3±0.2mV dec-1 and a lifetime of more than 1 year (over 3000 determinations for each membrane). The slope indicates that the ion-selective electrode responds preferentially to the Al(F)4- species. Application of this electrode for the aluminium(III) determination in stomach anti-acid samples is reported.

Influence of the medium (strongly acid or basic) over the electrochemical properties of the nitrate selective electrode

DEL TÓRO DÉNIZ,Rubén; RAJMANKO,E. M.; PEÓN ESPINOSA,Ana María; PEÑA VELÁZQUEZ,Inés
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 01/01/1997 EN
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A nitrate selective electrode was prepared for use in an aggresive medium (high acidic or basic concentration). It is demonstrated that the depending E graph with respect to pNO3- has not a Nernstian response in concentration acidic range upper 0.1 mol/L H2SO4. The observed behaviour is supposed to be due to the formation of a dimeric anion HN2O6-.

Use of a Ca-selective electrode in the determination of total Ca in the production of crude sugar. Preliminary studies

GONZÁLEZ GARCÍA,Jorge; EGONOV,V.V.; DEL TÓRO DÉNIZ,Rubén; DEL TÓRO DÉNIZ,E.; MARTINÉZ SÁEZ,S.; RAMOS VEGA,A.
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 01/01/1997 EN
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The determination of the total calcium in juice, syrups, and other products of the sugar industry is investigated. Total calcium and free calcium is determinated by AAS and employing Ca-selective electrode respectively. A coefficient is obtained for the relation of total calcium with respect to free calcium. The coefficient is employed to determine the content of total calcium in accordance with the following equation.15e.gif (673 bytes)

Determination of acetylsalicylic acid in tablets with salicylate ion selective electrode in a Batch Injection Analysis system

Fernandes,Julio Cesar B.; Garcia,Carlos Alexandre B.; Grandin,Luciane A.; Oliveira Neto,Graciliano de; Godinho,Oswaldo E.S.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/05/1998 EN
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98.61188%
The feasibility of the use of a Batch Injection Analysis (BIA) system for potentiometric determination of acetylsalicylic acid in tablets, with a membrane ion selective electrode, was investigated. There is no significant difference between the results obtained by the proposed method and those obtained by the Standard British Pharmacopaeia method12 at the 95% confidence level. Values of 4% and 2.5% for R.S.D. were obtained by the application of the BIA-potentiometric method and for the injections respectively. About 90 determinations per hour can be performed with the proposed BIA potentiometric method.

Ion-Selective Electrode for the Determination of Iron(III) in Vitamin Formulations

Teixeira,Marcos Fernando de S.; Aniceto,Clezio; Fatibello-Filho,Orlando
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/1998 EN
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A coated graphite-epoxy ion-selective electrode for iron(III), based on the ion-pair formed between [Fe(citrate)2]3- and the tricaprylylmethylammonium cation (Aliquat 336) in a poly(vinylchloride) (PVC) matrix has been constructed. A thin membrane film of this ion-pair, dibutylphthalate (DBPh) in PVC was deposited directly onto a Perspex® tube, which contained a graphite-epoxy conductor substrate. The coating solution was prepared by dissolving 30% (w/w) of PVC in 10 mL of tetrahydrofuran following addition of 65% (w/w) DBPh and 5% (w/w) of the ionic pair. The effect of pH, citrate concentration and some cations on the electrode response has been investigated. The E(mV) vs. log [Fe(citrate)2]3- electrode response was linear for iron(III) concentration from 1.0 x 10-3 mol/L to 1.0 x 10-1 mol/L in 1.0 mol/L citrate medium, with a slope of 19.3 ± 0.5 mV/decade and a useful lifetime of at least six months (more than 800 determinations for each polymeric membrane used). The detection limit was 7.5 x 10-4 mol/L and the relative standard deviation was less than 3% for a solution containing 5.0 x 10-3 mol/L of iron(III) (n = 10). The application of this electrode for iron(III) determination in samples of vitamin formulations is described. The results obtained with this procedure are in close agreement with those obtained using AA spectrophotometry (r = 0.9999).

Fabrication of a new samarium(III) ion-selective electrode based on 3-{[2-oxo-1(2h)-acenaphthylenyliden]amino}-2-thioxo -1,3-thiazolidin-4-one

Zamani,Hassan Ali; Ganjali,Mohammad Reza; Adib,Mehdi
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2007 EN
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This paper introduces the development of an original PVC membrane electrode, based on 3-{[2-oxo-1(2H)-acenaphthylenyliden]amino}-2-thioxo-1,3-thiazolidin-4-one (ATTO) which has revealed to be a suitable carrier for Sm3+ ions. The resulting data illustrated that the electrode shows a Nernstian slope of 19.3 ± 0.6 mV per decade for Sm3+ ions over a broad working concentration range of 1.0 × 10-6 to 1.0 × 10-1 mol L-1. The lower detection limit was found to be equal to (5.5± 0.3) × 10-7 mol L-1 in the pH range of 3.57.5, and the response time was very short (~10 s). The potentiometric sensor displayed good selectivities for a number of cations such as alkali, alkaline earth, transition and heavy metal ions.

Potentiometric coated wire electrode for salicylate based on zinc(II) acetylacetonate

Ardakani,M. Mazloum; Pourhakkak,P.; Salavati-Niasari,M.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2007 EN
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A coated-wire ion selective electrode based on zinc(II) acetylacetonate as ionophore exhibited linear response with Nernstian slope of -59.6 ± 1.0 mV/decade over a wide concentration range (1.0´10-5-1.0´10-1 mol L-1). This electrode has 5.0´10-6 mol L-1 detection limit. The proposed electrodes has a response time between 5-10 s to achieve a 95% steady potential for salicylate concentrations. The electrode was suitable for use in aqueous solutions in a wide pH range of 2.7 to 7.8. The electrode life time was tested over a period of two months to investigate its stability. No significant change in the performance of the electrode was observed during this period, but after two months, a gradual decrease ocurred in the slope. The proposed electrode showed high selectivity for salicylate over a number of common inorganic and organic anions. The electrode was successfully applied to the determination of salicylate in pharmaceutical samples.

Fluoride determination in carbon nanotubes by ion selective electrode

Antes,Fabiane G.; Pereira,Juliana S. F.; Spadoa,Laurien C.; Muller,Edson I.; Flores,Erico M. M.; Dressler,Valderi L.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2012 EN
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Fluoride determination by ion selective electrode (ISE) in carbon nanotubes (CNTs) is proposed after pyrohydrolysis decomposition. Up to 1 g of CNTs could be decomposed improving the limit of detection (1.5 μg g-1), precision (RSD < 5%) and accuracy (agreement higher than 95% with values of certified reference materials (CRMs) and microwave-induced combustion (MIC)). Fluoride could be absorbed in water and the resulting solution can be analyzed by ISE. Pyrohydrolysis is easy to be performed and does not require any sophisticated instrumentation, which is attractive for routine fluoride control in CNTs.

Bacterial oxidation of polythionates: determination of tetrathionate with an ion-selective electrode.

Tuovinen, O H; Nicholas, D J
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /02/1977 EN
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A commercially available ion-selective electrode for nitrate was used to continuously monitor tetrathionate oxidation by Thiobacillus dentrificans. The electrode was much more sensitive to tetrathionate than to nitrate. The same electrode could also be used for the determination of trithionate.

Nitrate Ion-Selective Electrode in Microbial Media

Manahan, Stanley E.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/1969 EN
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A nitrate ion-selective electrode has been used to follow the kinetics of the reduction of nitrate by a bacillus isolated from the rumen of a sheep. The electrode system and the microbial culture were found to be quite compatible, although the formation of nitrite limits the utility and precision of the measurement. The formation of nitrite was followed simultaneously by a colorimetric method. Nitrate was converted quantitatively to nitrite. The rate of the reaction was found to increase to a plateau value, then drop abruptly when the nitrate was exhausted.

Validation of an ion selective electrode system for the analysis of serum fluoride ion

Duly, Ellie B.; Luney, Stephen R.; Trinick, Thomas R.; Murray, James M.; Comer, John E. A.
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
Publicado em //1995 EN
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A high impedance unit was developed for use with a fluoride/pH electrode system for the measurement of serum fluoride. The linearity, accuracy, precision and detection limit of the system is reported. At a pH of 1.55, the system was linear over a range of serum fluoride concentrations up to 100 μmol l-1, with a lower limit of detection of 0.3 μmol l-1. Recoveries at this pH were 94-105% in the range 2.6-100 μmol l-1. Within-run CVs ranged from 4.2% at a level of 2.3 μmol l-1 to 1.2% at a level of 55.7 μmol l-1, while day-to-day CVs ranged from 12.8% at a level of 2.2 μmol l-1 to 4.6% at a level of 51.7 μmol l-1. The system demonstrated a rapid response time and has the potential for a smaller sample size requirement with alternative electrode shape. Continued development of this unit into an automated fluoride ion selective electrode system is recommended, since the measurement of serial serum fluoride samples is of greatest importance in assessing the impact of new anaesthetic agents on renal function.

Étude fonctionnelle du cotransporteur Na+/glucose (hSGLT1) : courant de fuite, vitesse de cotransport et modélisation cinétique

Longpré, Jean-Philippe
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
FR
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Les résultats présentés dans cette thèse précisent certains aspects de la fonction du cotransporteur Na+/glucose (SGLT1), une protéine transmembranaire qui utilise le gradient électrochimique favorable des ions Na+ afin d’accumuler le glucose à l’intérieur des cellules épithéliales de l’intestin grêle et du rein. Nous avons tout d’abord utilisé l’électrophysiologie à deux microélectrodes sur des ovocytes de xénope afin d’identifier les ions qui constituaient le courant de fuite de SGLT1, un courant mesuré en absence de glucose qui est découplé de la stoechiométrie stricte de 2 Na+/1 glucose caractérisant le cotransport. Nos résultats ont démontré que des cations comme le Li+, le K+ et le Cs+, qui n’interagissent que faiblement avec les sites de liaison de SGLT1 et ne permettent pas les conformations engendrées par la liaison du Na+, pouvaient néanmoins générer un courant de fuite d’amplitude comparable à celui mesuré en présence de Na+. Ceci suggère que le courant de fuite traverse SGLT1 en utilisant une voie de perméation différente de celle définie par les changements de conformation propres au cotransport Na+/glucose, possiblement similaire à celle empruntée par la perméabilité à l’eau passive. Dans un deuxième temps...

Duodenogastric reflux after gastric surgery and in gastric ulcer disease: continuous measurement with a sodium ion selective electrode.

Smythe, A; O'Leary, D; Johnson, A G
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /08/1993 EN
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Duodenogastric reflux (DGR) was investigated with a sodium ion selective electrode in 10 normal controls, 10 patients with persistent pain after gastric surgery, and five patients with gastric ulcer. During an average study time of two and a half hours, normal controls had reflux for 12% of the study, whereas patients after gastric surgery had reflux for 91% of the study time (p < 0.0002). Patients with a gastric ulcer had reflux on average for 67% of the study (p < 0.001). The patients who had had gastric surgery had several symptoms, but there was no association between the number or nature of symptoms and the severity of DGR as determined by the sodium electrode. Patients with positive bile provocation tests did not show any significant difference in the duration of reflux compared with those with a negative provocation test (79% and 87%). There was also no relation between the results of the provocation test and the number and nature of symptoms. Continuous monitoring of intragastric sodium ions with a selective electrode is a practical means of assessing DGR. Results suggest that symptoms due to DGR may be related to the sensitivity of the gastric lining as well as the amounts of duodenal contents flowing back into the stomach.

Determination of nitrate in drinking water by ion-selective electrode.

Cortés Nodarse, I.; Lazo, A. R.; Serrano M., M.; Yazdani-Pedram Zobeiri, Mehrdad; Arada Pérez, María de los Angeles
Fonte: Ministerio de Educación Superior Publicador: Ministerio de Educación Superior
Tipo: Artículo de revista
ES
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Nitrate concentration in drinking water was directly determined by employing an ion selective liquid membrane electrode (ISE). This was constructed with poly(vynil chloride) as matrix on a solid conducting support. Tetra-decyl ammonium nitrate (TDAN) was used as ionophore and dibutyl phthalate as plasticizer and solvent-mediator. The constructed ISE showed Nernstian slope with value of-61,2+-0,2 mV/dec-1, practical detection limit (PDL) of9,59 · 10-6 mol/dm3, lower limit of linear response (LLLR) of 2,82 · 10-5 mol/dm3,pH range of 5,0-11,5 life-time of >6 months without any divergence and with stable response of 15 seconds. Determination of nitrate ion concentration in drinking water was preformed by direct potentiometric method. Reliability of the electrode was evaluated by measuring the nitrate concentration by ion chromatography as a comparative method. The results showed good agreement between the values obtained by both methods, indicating the applicability of the proposed electrode for accurate determination of nitrate concentration in drinking water, where the measured values were less than 10 mg/L.

Construction and characterization of a lead(II) ion selective electrode with 1-furoil-3,3-diethylthiourea as neutral carrier

Arada, M. A.; Bustamante, M.; Jiménez, J.; Yazdani-Pedram Zobeiri, Mehrdad; Lazo, A. R.
Fonte: ASOC QUIMICOS, INST QUIMICO SARRIA Publicador: ASOC QUIMICOS, INST QUIMICO SARRIA
Tipo: Artículo de revista
EN
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Lead(II) ion selective electrode, ISE, based on plasticized PVC membranes with 1-furoyl 3,3 diethyl thiourea as ionophore and tributylphosphate as plasticizer have been developed. The membrane was applied on a conducting epoxy resin support. Some parameters of evaluation of the electrode are presented in this work. The ISE have linear response in the concentration range of the 10(-6)-10(-3) mol/dm(3), with slope of 29.61 mV/decade. The static response time obtained was less than 20 seconds. The ISE is useful for more than one month. The selectivity coefficients (K-AB(Pot)) for Cu2+, Cd2+ and Ca2+ ions were calculated by employing the mixed solutions method and the pH dependence of the potential was analyzed. Scanning electron microscopy (SEM) of the membranes was registered at different time of the use of the ISE. The SEM images showed morphological changes of the membrane surface probably due to both the reaction between the Pb2+ and the ionophore and/or loss of the membrane components by exudation.