Academic literature on the topic 'Amperometric titration'

AbstractA new amperometric titration method was developed for quantitative determination of ferrate(VI) (FeVIO42−) in the 7.06×10−5−5.73×10−3 M concentration range. Chromium(III) hydroxide solution was used as the titrant. The diffusion current (Id) had a linear relationship with the concentration of ferrate(VI) and slopes were dependent on the concentration of NaOH. The amperometric titration could detect a lower concentration of ferrate(VI) than could potentiometric and colorimetric titrations. The method was applied successfully to determine concentrations of ferrate(VI), generated electrochemically, in strong alkaline solutions.

AbstractInterrupted amperometry is a new highly sensitive method for diffusion current measuring. The main feature of the proposed technique is the use of capacitive current as the analytical signal together with the faradaic current. The conventional electrical circuit for amperometric measurements is complemented by a switcher that enables periodical interruption of the circuit. The technique was successfully applied for direct amperometric determination of lead, cadmium and iron ions, phenol and hydroquinone; for determination of dichromate ion via titration; for determination of dissolved oxygen in water by Clark-type sensor. In all the mentioned cases the achieved values of analytical characteristics are significantly better than for conventional amperometric methods. There are limitations and perspectives of the proposed technique considered.

Determination of chloride contents in aqueously isolated chloroplasts from spinach by amperometric titration indicated chloride concentrations of 60 to 100 mmol 1-1 (based on a chloroplast volume of 25 μl mg-1 chlorophyll). However, when analyzed by anion chromatography, chloride contents in chloroplasts were much lower (1-8 mmol 1-1). In leaf extracts chloride concentrations obtained with both methods were rather similar. Boiling of chloroplast extracts prior to chloride titration reduced indicated chloride contents by a factor of three or four, but did not change results obtained with anion chromatography. It is concluded that chloroplasts contain large amounts of silver complexing agents giving rise to a drastic overestima­tion of chloroplast chloride concentrations when measured by amperometric titration. Boiling and centrifugation of extracts apparently precipitates these compounds only insufficiently.

A new electroanalytical method has been developed for the quantitative determination of crocin in a sample of stigmas of saffron (Crocus sativus L.). Crocin is polarographically inactive. However, cysteine in 0.02 M NaCl, pH=5.2±0.01 produces a well defined wave/peak with E1/2/Ep= –0.47/–0.45 V vs. Ag/AgCl. On recording polarograms of a set of solution containing a fixed concentration of cysteine and varying concentrations of crocin under aforesaid experimental conditions a gradual decrease in peak height/diffusion current and a negative shift in peak potential was observed. Thus, indicating cysteine-crocin interaction. Amperometric titration indicated crocin to cysteine ratio of 1:2. The above amperometric titration procedure has been used to determine the concentration of crocin in a sample of saffron. Crystallization process was carried out for the extraction of crocin from dried powder of saffron stigmas. The crystallized crocin was identified by UV-Visible spectrophotometry(at 255 nm and 442 nm) and the quantitative analysis by the developed amperometric method. The concentration of crocin in saffron was found to be 2.13% and purity of isolated crocin 96.81%. The percent recovery varied from 98.56–100.31% and RSD (n=5) of 2.17%.The validation of the proposed procedure for the quantitative assay of crocin was examined via an evaluation of the repeatability, recovery, selectivity and relative standard deviation.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico
Considerando que no Brasil o uso de diÃxido de cloro no tratamento de Ãgua à ainda pouco adotado em funÃÃo tanto de seu alto custo quanto da dificuldade de sua quantificaÃÃo, pretendemos comparar trÃs metodologias usadas para quantificar esse produto. Escolhemos a metodologia LGB (Lissamine Green B) e a comparamos com a metodologia EPA 327.0 ((Environmental Protection Agency) e a TitulaÃÃo AmperomÃtrica (referenciadas), ambas analisadas sob a mesma diluiÃÃo. Isso posto, visamos tambÃm comparar os efeitos da variaÃÃo da diluiÃÃo especificamente na metodologia TitulaÃÃo AmperomÃtrica. Para a metodologia de anÃlise, utilizamos o teste F, para analisar a precisÃo; o teste de ponto de HipÃtese, para analisar a exatidÃo entre as metodologias e a possÃvel existÃncia de tendÃncia entre elas; o teste T, para analisar a existÃncia de erros sistemÃticos entre as metodologias; o teste ANOVA one-way, para determinar os efeitos de diluiÃÃo na TitulaÃÃo AmperomÃtrica. A comparaÃÃo realizada nos permite concluir que a metodologia LGB nÃo apresentou variÃncia de repetibilidade e precisÃo intermediÃria pior que a apresentada na metodologia EPA 327.0 e na metodologia TitulaÃÃo AmperomÃtrica no nÃvel de confianÃa de 95%, apesar da dispersÃo em relaÃÃo à mÃdia e à mediana.
Considering that in Brazil the use of chlorine dioxide in water treatment is still not adopted due to both its high cost and difficulty of its quantification, we intend to compare three methods used to quantify this product. We chose the methodology LGB (not referenced) and compared with the EPA method 327.0 (Environmental Protection Agency () and amperometric titration (referenced), both analyzed under the same dilution. With that in mind, we aim to also compare the effects of varying the dilution specifically the methodology amperometric titration. for the analysis methodology, we use the F test to determine the accuracy, the test point hypothesis, to determine the accuracy of the methodologies and the possible existence of a tendency among them, the t test to analyze the existence of systematic errors among methods, the one-way ANOVA test to analyze the effects of dilution in the amperometric titration. The comparison allowed us to conclude that the methodology did not provide LGB variance of repeatability and intermediate precision worse than the one presented in the methodology EPA method 327.0 and the amperometric titration level of 95%, despite the dispersion from the mean and median.

A potencialidade do eletrodo de cobre em meio alcalino foi demonstrada para o determinação de etanol a +0,6 V vs Ag/AgCl. A participação de espécies solúveis de Cu(III) no processo eletrocatalítico envolvendo a oxidação do etanol foi demonstrada por experimentos utilizando eletrodo disco-anel. A influência do potencial de pré-tratamento no sinal anódico foi investigada e correlacionada com a morfologia dos filmes formados na superfície do eletrodo por EDS (Energy Dispersive X-Ray Spectroscopy), indicando que as espécies de Cu(III) são originadas a partir da oxidação da camada de CuO. As medidas de etanol foram realizadas por amperometria em 0,6 V (vs Ag/AgCl). A repetibilidade das medidas utilizando padrão aquoso de etanol 0,05 % (v/v) foi de 3 % (v/v) e os limites de detecção e quantificação foram de 0,005 % (v/v) e 0,01 % (v/v), respectivamente. Nas condições experimentais otimizadas, o sensor amperométrico foi utilizado para o monitoramento da concentração de etanol no ar exalado (BrAC), que foi convenientemente coletado em um balão de borracha (V = 3 L) e introduzido em uma solução de NaOH 1 mol L-1 (V = 10 mL). O sensor apresentou uma faixa linear para concentrações de etanol em ar exalado na faixa de 0,26 – 130 mg L-1, operando de acordo com os parâmetros analíticos especificados na Legislação Brasileira para a quantificação de etanol no ar exalado em condutores de veículos automotores. A constante de eliminação de etanol do corpo humano também foi investigada e os resultados concordaram com os valores da literatura. Empregando-se eletrodos de Cu e Au foram também desenvolvidas outras metodologias para a quantificação de dipirona, glicose e ácido ascórbico e sistemas em fluxo. Estudos sobre o desenvolvimento e propriedades de um sistema gerador-coletor foram realizados e o dispositivo foi utilizado em titulações de substâncias redutoras com iodo gerado eletroquimicamente.
A copper disc working electrode in alkaline solutions was demonstrated to act as a suitable amperometric sensor for ethanol determination at +0.6 V vs Ag/AgCl. The participation of free-soluble Cu(III) species in the electrocatalytic process involving the anodic oxidation of ethanol has been demonstrated by rotating ring-disc electrode voltammetry. The influence of the pretreatment potential on the anodic signal was investigated and a correlation with the morphology of the electrode surface characterized by Energy Dispersive X-Ray Spectroscopy (EDS) indicated that the Cu(III) species is originated from the oxidation of a CuO layer. Ethanol measurements were performed in the amperometric mode at 0.6 V (vs Ag/AgCl). The repeatability of the measurements for a 0.05 % aqueous ethanol solution was estimated as 3 %, and the detection and quantification limits were determined as 0.005 % and 0.01 %, respectively. At the optimum experimental conditions, the amperometric sensor was used to monitor the concentration of ethanol in breath (BrAC), which was conveniently collected in a rubber air balloon (volume = 3 L) and introduced in a 1 mol L-1 NaOH working solution (volume = 10 mL). The sensor can measure a person\'s breath ethanol over the concentration range 0.26 - 130 mg L-1 by operating it according to an established protocol, of which the analytical parameters are specified by the Brazilian Legislation for BrAC measurements in drivers. The rate of ethanol degradation in the body was followed, and the results agree with predictions in the literature. Methodologies for the determination of dipyrone, glucose and ascorbic acid were also developed by using Cu and Au electrodes. Features of a dual-band electrochemical cell were investigated towards the development of a generator-collector system, which was employed in titrations with electrogenerated iodine.