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Determination of the surface charge density of a mercury electrode by extrusion: a new method for correction of the faradaic component

Brito, Maria S. L.; Angnes, Lúcio; Brett, Christopher M. A.; Gutz, Ivano G. R.
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
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The accurate determination of the surface charge density at the mercury | solution interface by the method of extrusion of mercury drops is impaired by the faradaic current caused by traces of electroactive species. This paper describes a new design of a hanging mercury drop electrode with accurate control of the extruded electrode area, to within 0.1%, together with a new and reliable procedure for correction of the faradaic current. The procedure is based on first obtaining the correction parameters in the presence of increasing amounts of electroactive species and then using these parameters for correction of the faradaic component so as to obtain the surface charge density of the electrode. Implementation of the method with a microcomputer controlled system provides automatic acquisition of corrected electrode charge density values as a function of the electrode potential. The results obtained with this new method are in excellent agreement with those obtained by other methods, as illustrated for aqueous sodium fluoride solution.; http://www.sciencedirect.com/science/article/B6TGB-3WS6M1X-4/1/959396100ce50f29fe3e81cc9a422423

Development of a sequential injection-square wave voltammetry method for determination of paraquat in water samples employing the hanging mercury drop electrode

SANTOS, Luciana B. O. dos; INFANTE, Carlos M. C.; MASINI, Jorge C.
Fonte: SPRINGER HEIDELBERG Publicador: SPRINGER HEIDELBERG
Tipo: Artigo de Revista Científica
ENG
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This work describes the development and optimization of a sequential injection method to automate the determination of paraquat by square-wave voltammetry employing a hanging mercury drop electrode. Automation by sequential injection enhanced the sampling throughput, improving the sensitivity and precision of the measurements as a consequence of the highly reproducible and efficient conditions of mass transport of the analyte toward the electrode surface. For instance, 212 analyses can be made per hour if the sample/standard solution is prepared off-line and the sequential injection system is used just to inject the solution towards the flow cell. In-line sample conditioning reduces the sampling frequency to 44 h(-1). Experiments were performed in 0.10 M NaCl, which was the carrier solution, using a frequency of 200 Hz, a pulse height of 25 mV, a potential step of 2 mV, and a flow rate of 100 mu L s(-1). For a concentration range between 0.010 and 0.25 mg L(-1), the current (i(p), mu A) read at the potential corresponding to the peak maximum fitted the following linear equation with the paraquat concentration (mg L(-1)): ip = (-20.5 +/- 0.3) Cparaquat -(0.02 +/- 0.03). The limits of detection and quantification were 2.0 and 7.0 mu g L(-1)...

Pendimethalin determination in natural water, baby food and river sediment samples using electroanalytical methods

GALLI, Andressa; SOUZA, Djenaine De; MACHADO, Sergio A. S.
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
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This work describes the electroanalytical determination of pendimethalin herbicide levels in natural waters, river sediment and baby food samples, based on the electro-reduction of herbicide on the hanging mercury drop electrode using square wave voltammetry (SWV). A number of experimental and voltammetric conditions were evaluated and the best responses were achieved in Britton-Robinson buffer solutions at pH 8.0, using a frequency of 500 s(-1). a scan increment of 10 mV and a square wave amplitude of 50 mV. Under these conditions, the pendimethalin is reduced in an irreversible process, with two reduction peaks at -0.60 V and -0.71 V. using a Ag/AgCl reference system. Analytical curves were constructed and the detection limit values were calculated to be 7.79 mu g L(-1) and 4.88 mu g L(-1), for peak 1 and peak 2, respectively. The precision and accuracy were determinate as a function of experimental repeatability and reproducibility, which showed standard relative deviation values that were lower than 2% for both voltammetric peaks. The applicability of the proposed methodology was evaluated in natural water, river sediments and baby food samples. The calculated recovery efficiencies demonstrate that the proposed methodology is suitable for determining any contamination by pendimethalin in these samples. Additionally...

Estudos de adsorção e equilíbrio nos sistemas Cd(II) / SCN-/ C6H12N4 e Cd(II)/I-/SCN-. aperfeiçoamento de métodos e eletrodo; Adsorption and equilibrium studies of the systems Cd(II)/SCN-/C6N12H14 and Cd(II)/I-/SCN-. Improvement of methods and of the electrode

Angnes, Lucio
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 07/12/1987 PT
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Na presente tese investigou-se a adsorção induzida de um cátion metálico (cádmio(II)) na presença simultânea de dois ligantes (um pseudo-haleto e uma amina ou haleto) na interface eletrodo de mercúrio/solução aquosa, com vistas a uma melhor compreensão desse processo. Os estudos de adsorção foram precedidos por estudos de equilíbrio dos compostos de coordenação formados em solução aquosa. Medidas experimentais foram feitas por potenciometria com eletrodo de amálgama, em força iônica 1,00 M, ajustada com NaCl04. Análise dos dados por programas computacionais adequados levou à quantificação das constantes de estabilidade de 7 espécies binárias e 9 espécies mistas para o sistema Cd(II)/ SCN-/C6H12N4 e de 8 espécies binárias e 6 mistas para o sistema Cd(II)/I-/SCN-, sendo todas estas espécies mononucleares. Para possibilitar um maior grau de automação das medidas cronocoulométricas de adsorção, o eletrodo de gota pendente de mercúrio, anteriormente desenvolvido no IQ-USP, teve seu sistema mecânico aperfeiçoado e passou a ser controlado por computador. O "software" se incumbe de calcular e comandar o tempo de abertura da micro-válvula do eletrodo para gerar gotas com a área solicitada. Aproveitando a possibilidade de realizar aquisição (de dados de carga durante e após a formação das gotas de mercúrio...

Cathodic stripping voltammetric determination of ceftazidime in urine at a hanging mercury drop electrode

Ferreira, V. S.; Zanoni, Maria Valnice Boldrin; Fogg, A. G.
Fonte: Academic Press Inc. Jnl-comp Subscriptions Publicador: Academic Press Inc. Jnl-comp Subscriptions
Tipo: Artigo de Revista Científica Formato: 115-122
ENG
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A method was developed for the differential-pulse cathodic stripping voltammetric determination of ceftazidime with a hanging mercury drop electrode using its reduction peak at -0.43 V in Britton-Robinson buffer pH 4.0. The optimum accumulation potential and time were -0.15 V and up to 60 s, respectively. Linear calibration graphs were obtained from 1 x 10(-8) M and 1.5 x 10(-7) M. The limit of determination was calculated to be 5 x 10(-9) M. The coefficient of variation was 4% (n = 7) at 1 x 10(-7) M ceftazidime. The effect of various components of urine on the voltammetric response was studied, and creatinine, uric acid, urea, and glucose were shown to interfere in the method. Ceftazidime bound to human albumin gives a unique stripping peak at -0.48 V. Recoveries of 87% +/- 2% of the ceftazidime (n = 5) were obtained from urine spiked with 1.27 mu g ml(-1) using C-18 solid phase extraction cartridges. (C) 1997 Academic Press.

Cathodic stripping voltammetric detection and determination at a hanging mercury-drop electrode of dye contaminants in purified biomaterials: study of the human serum albumin and reactive dye 120 system

Guaratini, CCI; Zanoni, Maria Valnice Boldrin; Fogg, A. G.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 65-72
ENG
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Procion red HE-3B (RR120) is an example of dye currently used in affinity purification. A method is described for determining trace amounts of RR120 dye contaminant in human serum albumin by cathodic stripping voltammetry. The method is based on a measure of a well-defined peak at -0.58 V, obtained when samples of HSA protein (0.01-2% w/v) containing dye concentrations are submitted to a heating time of 330 min at 80degreesC in NaOH, pH 12.0 and the samples are removed to a solution containing Britton-Robinson buffer, pH 4.0. Using an optimum accumulation potential and tune of 0 V and 240 s, respectively, linear calibration curves were obtained from 1.0 X 10(-9) to 1.0 X 10(-8) mol 1(-1) for RR120 dye. Leakage/hydrolysis of reactive red 120 from an agarose support (e.g. at pH 2 or 12) can also be conveniently determined at very low levels (sub-mug ml(-1)) by means of cathodic stripping voltammetry, which involves adsorptive accumulation of the dye onto the hanging mercury-drop electrode. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Indirect cathodic-stripping voltammetric determination of ceftazidime as a mercury salt

Ferreira, V. S.; Zanoni, Maria Valnice Boldrin; Fogg, A. G.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 255-259
ENG
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At accumulation potentials close to +0.1 V at a hanging mercury drop electrode, ceftazidime is accumulated at pH 9.5, probably in a hydrolysed or otherwise chemically altered form, in an anodic process to give an adsorbed mercury salt. The accumulation of this mercury salt allows the indirect cathodic-stripping voltammetric determination of ceftazidime using the reduction peak of the mercury salt at -0.70 V. The high sensitivity of the method coupled with high sample dilution allows ceftazidime to be determined in milk samples at the 28 mu g ml(-1) level without prior separation. In order to determine lower levels of ceftazidime in milk (ca. 10 ng ml(-1)) a separation process would be required. (C) 1998 Elsevier B.V. B.V. All rights reserved.

Cathodic stripping voltammetric determination of ceftazidime with reactive accumulation at a poly-L-lysine modified hanging mercury drop electrode

Ferreira, V. S.; Zanoni, Maria Valnice Boldrin; Fogg, A. G.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 159-166
ENG
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Ceftazidime is hydrolysed only slowly at pH 10 at room temperature. This is indicated by a small cathodic stripping voltammetric peak obtained at pH 10 at a hanging mercury drop electrode at about -0.6 V which corresponds to the reduction of the hydrolysis product. This peak is enhanced more than tenfold by the addition of poly-L-lysine (PLL) to the electrolyte solution. The optimum accumulation potential is between 0 and -0.1 V: the size of the peak decreases steadily, however, as the accumulation potential is moved to more negative potentials and is about one-sixth the size for accumulation at -0.4 V. Existing knowledge of the organic chemistry of cephalosporins indicates that the accumulation must involve an aminolysis reaction of the unprotonated PLL with the beta-lactam ring of the ceftazidime. The limit of detection (3 sigma) in standard solutions was calculated to be 1 x 10(-10) mol l(-1). The detection limit in buffer solution containing 1% of urine was calculated to be 5 x 10(-9) mol l(-1), i.e. 5 x 10(-6) mol l(-1) in the urine. (C) 1999 Elsevier B.V. B.V. AU rights reserved.

Cathodic stripping voltammetric determination of cefaclor in pharmaceutical formulations

Rodrigues, LNC; Fogg, A. G.; Zanoni, Maria Valnice Boldrin
Fonte: Marcel Dekker Inc Publicador: Marcel Dekker Inc
Tipo: Artigo de Revista Científica Formato: 97-109
ENG
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A sensitive method is described for the determination of cefaclor by cathodic stripping voltammetry at the hanging mercury drop electrode. cefaclor is accumulated at the electrode surface as a mercury salt, which is reduced at -0.67 V. The optimum accumulation potential and accumulation time were +0.15 V and up to 180 s, respectively. Linear calibration graphs were obtained between 3.9 mu g.L-1 to 39 mu g.L-1 and the limit of determination was evaluated to be 1.9 mu g.L-1. The method was applied successfully to the determination of cefaclor in pharmaceutical formulations.

Aspects of cathodic stripping voltammetry at the hanging mercury drop electrode and in non-mercury disposable sensors

Fogg, A. G.; Zanoni, Maria Valnice Boldrin; Barros, A. A.; Rodrigues, J. A.; Birch, B. J.
Fonte: Wiley-Blackwell Publicador: Wiley-Blackwell
Tipo: Revisão Formato: 1227-1232
ENG
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Cathodic stripping voltammetry (CSV) and accumulation at the hanging mercury drop electrode are reviewed briefly. Proposals in a recent IUPAC technical report are considered. Three recent developments in CSV are discussed: the adaptation of CSV methods developed for use with the hanging mercury drop electrode for use with screen-printed carbon electrodes in disposable sensors, the use of reactive accumulation, and the chemometric use of kinetic methods of determination with pulse methods in CSV.

Thin mercury film electrodes in dynamic speciation studies of metals

Rocha, Luciana Sarabando da
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Dissertação de Mestrado
ENG
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No presente trabalho, foi avaliado o desempenho e a aplicabilidade do eléctrodo de filme fino de mercúrio, em estudos de especiação dinâmica de metais vestigiais. Para tal, foram utilizadas duas técnicas electroanalíticas de redissolução: a clássica Voltametria de Redissolução Anódica (ASV) e a recentemente desenvolvida, Cronopotenciometria de Redissolução com varrimento do potencial de deposição (SSCP). As propriedades de troca-iónica e de transporte de massa de películas mistas preparadas a partir de dois polímeros com características distintas, o Nafion (NA) e o 4-Poliestireno sulfonato de sódio (PSS), foram avaliadas, antes da sua aplicação no âmbito da especiação de metais. Estas películas de NA-PSS demonstraram uma elevada sensibilidade, reprodutibilidade, estabilidade mecânica, bem como, propriedades de anti-bloqueio adequadas na modificação química do eléctrodo de filme fino de mercúrio (TMFE) e, na sua aplicação na determinação de catiões metálicos vestigiais em amostras complexas, por ASV. Para além disso, o desempenho de membranas do polielectrólito PSS em estudos de voltametria de troca-iónica (IEV) foi estudado. O objectivo desta investigação foi reunir as condições ideais na preparação de películas de PSS estáveis e com uma densidade de carga negativa elevada...

Electroreduction of dipyridamole at mercury-coated platinum microelectrode

Toledo,Renata A. de; Castilho,Marilza; Mazo,Luiz Henrique
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2004 EN
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The electroreduction of Dipyridamole (DIP) was studied in 0.10 mol L-1 phosphate buffer solution (pH 3.0) on a mercury coated platinum microelectrode (Hg-ME), employing cyclic, linear sweep voltammetry and polarography techniques. The similarity between Hg-ME voltammetric profile and the sigmoidal polarographic waves both with a diffusion limited current is showed. Experiments with a hanging mercury drop electrode (HMDE) were performed in parallel to confirm the results obtained with Hg-ME, which indicated that the reduction occurs in two irreversible steps involving two electrons and two protons each step. The limiting diffusion current, concerning the first step, allows estimating the diffusion coefficient for DIP as being equal to 2.04 x 10-5 cm² s-1.

Developing a continuous flow-square wave voltammetry method for determination of atrazine in soil solutions using the hanging mercury drop electrode

Santos,Luciana B. O. dos; Abate,Gilberto; Masini,Jorge C.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2006 EN
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This work describes the development of a Continuous Flow-Square Wave Voltammetry method for determination of atrazine using the hanging mercury drop electrode. The best signal to noise ratio was obtained at the square wave frequency of 350 Hz and flow rate of 0.47 mL min-1. Under these conditions, the analytical curve obtained in 0.010 mol L-1 CaCl2 soil extracts in presence of 40 mmol L-1 BR buffer and 0.25 mol L-1 NaNO3 was linear for atrazine concentrations between 0.10 and 2.0 µg mL-1, with detection and quantification limits of 0.030 and 0.10 µg mL-1, respectively. The proposed method increased the analytical throughput in comparison with the batch methodology, allowing a sampling frequency of 72 h-1 to be accomplished. Besides, the sample consumption is significantly reduced, and only 341 µL are necessary for each analysis. The results obtained were similar to the ones obtained by HPLC, but the proposed method is faster and does not use organic solvents.

Voltammetric behavior of amfepramone (diethylpropion) at the hanging mercury drop electrode and its analytical determination in pharmaceutical formulations

Carvalho,Leandro M. de; Nascimento,Paulo C. do; Bohrer,Denise; Correia,Daniele; Bairros,André V. de; Pomblum,Valdeci J.; Pomblum,Solange G.
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 describes a systematic study of the voltammetric behavior of amfepramone at the hanging mercury drop electrode (HMDE) by cyclic (CV) and alternating current (AC) voltammetric methods. The studies showed the adsorptive behavior of amfepramone at the HMDE and were performed in H2SO4 0.1 mol L-1 (pH 1.0) and Ringer buffer (pH 11.0) as supporting electrolytes. The linear range for the amfepramone determination by differential pulse voltammetry (DPV) was 0.05 to 2.0 mg L-1 (r = 0.998) in acidic medium and 0.25 to 4.0 mg L-1 (r = 0.994) in alkaline medium. The relative standard deviation calculated was 2.5% and 4.0 % for five measurements of 0.5 mg L-1 amfepramone in acidic and alkaline medium, respectively. The detection limits calculated for the amfepramone determination in acidic and alkaline medium were 0.035 e 0.18 mg L-1, respectively.The methods were applied for the determination of amfepramone by DPV in tablets and capsules of pharmaceutical formulations used in the treatment of obesity. Recoveries values ranging from 90.0 to 101.0% for amfepramone added to synthetic mixtures containing fenproporex, mazindol, sibutramine, fluoxetine, caffeine, diazepam, and metformin as interferents prove the applicability of the method for its determination in the presence of other drugs normally added illegally to pharmaceutical formulations commercialized as natural medicaments.

Square wave stripping voltammetry of titanium based on adsorptive accumulation of its hydroxynaphtol blue (HNB) complex at the static mercury drop electrode

Fraga, Isabel Cristina Serta; Ohara, Aniy K.; Farias, Pércio Augusto Mardini
Fonte: Inmetro - Instituto Nacional de Metrologia, Qualidade e Tecnologia Publicador: Inmetro - Instituto Nacional de Metrologia, Qualidade e Tecnologia
Tipo: Artigo de Revista Científica
ENG
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726.4597%
11 p. : il.; A new method is described for the determination of titanium based on the square wave adsorptive stripping voltammetry of Ti(IV) complexed with Hydroxynaphthol blue (HNB) at the static mercury drop electrode. Optimal conditions were found to be: preconcentration potential, −0.140 V vs. Ag/AgCl (KCl 3M); preconcentration time, 30 s (with stirring solution); pulse height, 75mV; frequency, 100 Hz; scan increment, 4mV; step time, 0.010 s; supporting electrolyte, acetate buffer (0.1 M, pH 3.2), and concentration of hydroxynaphthol blue, 1.0 × 10−5 M. The response of the system was found to be linear in a range of Ti(IV) concentrations from 5.0 to 20.0 μg/L. The limit of detection was found to be 0.18 μg/L and the limit of determination to be 1.09 μg/L, both using 30 s of preconcentration time. The effects of various potential interferences were also studied including a variety of cations, anions, and organic surfactants. The merits of the procedure were demonstrated in the analysis of certified NIST SRM 1633b and 1646a samples.

Flow-through polarographic cell for flow-injection analysis. Determination of nifedipine in pharmaceutical formulations

Toral Ponce, María; Quiroz, Gabriela; Jaque, Pablo; Richter D., Pablo
Fonte: JOHN WILEY & SONS INC Publicador: JOHN WILEY & SONS INC
Tipo: Artículo de revista
EN
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Artículo de publicación ISI; A simple design of a polarographic flow-through cell is proposed in which a conventional dropping mercury electrode (DME) is used as working electrode, and a mercury pool and a platinum wire are used as the reference and counter electrodes, respectively. The mercury droplets falling from the DME coalesce with the pool, and a fairly constant hold-up cell volume is achieved by controlled removal of the mercury from the pool at an equivalent flow rate than that of the DME. The analytical features of the cell are illustrated by flow-injection (FI) determination of the nitro derivative nifedipine in pharmaceuticals. The flow-through defector can be used either amperometrically, under continuous flow operation, or voltammetrically in quiet solution, under continuous flow-stopped flow mode. Under continuous flow operation of;he eel!, the sampling rate obtained was 120 h(-1). The repeat-ability of the analytical signals, expressed as RSD, was always lower than 2.1%. The recovery of nifedipine in synthetic tablet formulations was 99.8 +/- 0.6%.

Unusual oxidative behavior of (.eta.5-C5R5)M(CO)2 (R = H, CH3; M = Rh, Co) complexes at mercury and platinum electrodes

Gennett, Thomas; Grzeszczyk, Elizabeth; Jefferson, Anne; Sidur, Kathy
Fonte: The American Chemical Society: Inorganic Chemistry Publicador: The American Chemical Society: Inorganic Chemistry
Tipo: Abstract Formato: 31371 bytes; application/pdf
EN_US
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The electrochemical oxidative behavior of a series of cyclopentadienyl and pentamethylcyclopentadienyl carbonyl complexes of rhodium and cobalt is described. The voltammetric, polarographic, and coulometric data from the oxidations of (n^5-C5H5)Rh(CO)2, (n^5-C5H5)Co(CO)2, (n^5-C5(CH3)5)CO(CO)2, and (n^5-C5(CH3)5)Rh(CO)2 are reported. The electrochemical experiments were conducted in methylene chloride at platinum and mercury electrodes. The cyclopentadienyl complexes (n^5-C5H5)Rh(CO)2 and (n^5-C5H5)CO(CO)2 exhibited oxidative behavior dependent on electrode material. At a platinum-bead electrode there was evidence that the organometallic solute adsorbs to the electrode surface, while at a hanging-mercury-drop electrode it was found that mercuric chloride formed at the surface of the electrode at potentials greater than 0.200 V vs. SCE. This HgC12 reacts with the solute to form an insoluble Lewis acid-base adduct, [Cl2Hg]*[M(CO)2(n^5-C5H5)], where M = Rh, Co. These adducts were also formed from the homogeneous oxidation of the organometallic solute with [(n^5-C5H5)2Fe] [PF6], but only when mercury was present in the solution. The pentamethylcyclopentadienyl complexes (n^5-C5(CH3)5)CO(CO)2 and (n^5-C5(CH3)5)Rh(CO)2 were found to undergo chemically reversible one-electron oxidations to relatively stable cation radicals at both platinum and mercury electrodes. There was no evidence of either pentamethylcyclopentadienyl compbx reacting with the mercuric chloride. Extended Huckel calculations were conducted on all four complexes. Correlations were seen between the experimental observations and Huckel predictions of adduct formation and radical stability.

Interferentes Endócrinos em Águas Naturais: Determinação Voltamétrica de 17alfa-Metiltestosterona; Endocrine Interfering in Natural Waters: Voltammetric Determination of 17alpha-methyltestosterone

Luciane Miranda; Universidade Estadual do Centro Oeste; Andressa Galli; Universidade Estadual do Centro Oeste; Sueli P. Quináia; Universidade Estadual do Centro Oeste
Fonte: Revista Virtual de Química Publicador: Revista Virtual de Química
Tipo: ; Formato: application/pdf
Publicado em 28/02/2014 EN
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Os hormônios sexuais incluindo o 17a-metiltestosterona (MT) pertencem ao grupo de compostos considerados disruptores endócrinos.  No entanto, poucos estudos reportam o hormônio MT em amostras ambientais. Nesse contexto, este trabalho descreve a determinação direta de MT em amostras de águas naturais baseado na electroredução, empregando o eletrodo de gota pendente de mercúrio e a voltametria de onda quadrada. DOI: 10.5935/1984-6835.20140029; The sex hormones including 17a-methyltestosterone (MT) are within a group of compounds considered as endocrine disruptors. However, few studies report the presence of hormone MT in environmental samples. In this context, this paper describes the direct determination of MT in water samples based on electroredution and employing the electrode hanging mercury drop and square wave voltammetry. DOI: 10.5935/1984-6835.20140029

A form of adsorptive pre-wave in a sampled dc polarography on a static mercury drop electrode

Komorsky-Lovri,Šebojka; Lovri,Milivoj
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2006 EN
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Theoretical analyses show that in a sampled dc polarography on the static mercury drop electrode the response may consist of a pre-wave and a main wave that are separated by a minimum. This is a general characteristic of electrode reactions complicated by strong adsorption of the product. A steep pre-wave and the minimum are the indications of Frumkin isotherm. A flat plateau of the pre-wave is a special case of the steep plateau which appears at lower reactant concentrations. If the adsorption is weak, the pre-wave and the main wave are usually merged into a single wave.

Voltammetric Analysis of Montelukast Sodium in Commercial Tablet and Biological Samples Using the Hanging Mercury Drop Electrode

Alghamdi,Ali F
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2014 EN
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Adsorptive stripping voltammetry was used to prospect the adsorption property of montelukast sodium (MKST) on the hanging mercury drop electrode (HMDE). Through appointing the adsorptive stripping voltammetric (AdSV) process, a sensitive electroanalytical method for the quantitative analysis of MKST was accomplished. A well-developed voltammetric peak was obtained in pH 10 Britton-Robinson buffer (B-R buffer) at -1.080 V. The cyclic voltammetric studies indicated that the reduction process was irreversible and primarily controlled by adsorption phenomena. The studies of the variation of adsorptive voltammetric peak current with buffer electrolyte, pH, accumulation time (t acc), accumulation potential (Eacc), sweep rate, pulse amplitude, square wave frequency, working electrode area and convection rate have evaluated in the recognition of optimal experimental conditions for MKST analysis. The studied electroanalytical signal showed a linear response for MKST in the concentration range 5×10-8 - 1×10-6 mol L-1 (r = 0.994). A detection limit of 4×10-9 mol L-1 with relative standard deviation of 1.1 RSD% and mean recovery of 102±2.0% were obtained. The possible interferences by several compounds usually present in the pharmaceutical formulation were also evaluated. The analytical quantification of MKST drug in commercially available pharmaceutical formulation and biological samples was electrochemically studied.