Análise potenciométrica de redissolução com ultramicroeletrodos: fundamentos e aplicações na determinação de metais traços. Quím. Nova [online]. 09/02/ la química analítica es la parte de la química que estudia, diseña, desarrolla, optimiza y aplica métodos y técnicas que se materializan en. fundamentos fisioquímicos grado farmacia us métodos químicos: son todos aquellos que se basan casi exclusivamente en reacciones químicas en los que la.

Author: Batilar Dalar
Country: Paraguay
Language: English (Spanish)
Genre: Personal Growth
Published (Last): 6 November 2011
Pages: 133
PDF File Size: 3.66 Mb
ePub File Size: 17.97 Mb
ISBN: 586-5-14218-458-6
Downloads: 97379
Price: Free* [*Free Regsitration Required]
Uploader: Akinozshura

It establishes the preference with which the sensor responds to the analyte in the presence of various interfering ions from the sample.

leslie hluz – Google+

At high and very low target ion activities there are deviations from linearity. Rio de Janeiro,vol. Each of them has got advantages and drawbacks, and there are not general rules pointing which method gives the true result. In this case and others, such as self-life studies, in which sample quantities are limited, potentiometric titration may be a very good alternative.

Free fatty acids are a measure of evaluating fats and oils, submitted to abusive conditions, besides being a quality characteristic of edible vegetable oils.

Meaning of “potenciometria” in the Portuguese dictionary

Rio de Janeiro,cap. No processo de refino, por ex.

This membrane can be prepared as: Typical calibration curve of a potentiometric sensor determined in this way is shown in figure 2. The observed detection limit is often governedby the presence of other interfering ions or impurities. There is also an alternative method of the selectivity determination called matchedpotential method MPM.

In practice the potential difference i. All the contents of this journal, except where otherwise noted, is licensed under a Creative Commons Attribution License. However, it should be potenciometeia out that a single time constant does not describe the potenxiometria of the electrode response function.


A useful slope can be regarded as [mV per decade] [mV per decade] for double charged ion respectively. If for example metal buffers are used to eliminate the effectswhich lead to the contamination of very dilute solutions it is possible to enhance the detection limit down to M. Positive values of log Kxy indicate the preference of an electrode for theinterfering ion.

Typically such a membrane contains an analyte-selective component whichis responsible for the recognition process.

Alterando as quantidades de amostra utilizadas. However, in certain applications the value of the electrode slope is not criticaland worse value does not exclude its usefulness. Industrial Processing of Cotton-Seed apud ref.

[Potencio & Conduto] Aula – Métodos Eletroquímicos e Titulação Potenciométrica (Guts)

Moreover, in many investigationsthe response time of the overall measuring system is determined, which influences on the response time of the Fundwmentos. Nova17 In practice, detection limit on the order of M is measured for most of ion-selective electrodes.

Typically, the electrode calibration curve exhibits linear response range between M and M. The experimental selectivity coefficients depend on fundametnos activity and a method of their determination. Most often it is expressed as potencioketria logarithm of Kxy. An examplary set-up for the measurement of electromotive force is precented in figure 1.

According to the nature of the binding sites, the membranes can be classified as: Dois tipos de potendiometria podem ter ocorrido: New York,cap. The theoretical valueaccording to the Nernst equation is: Europa’s Quality Acceptance apud ref. The linear range of the calibration curve is usually applied to potenciomeyria the activity of the target ionin any unknown solution. Services on Demand Journal. How to cite this article. An ion-selective membrane is the key component of all potentiometric ion sensors.


Different methods of the selectivity determination can be found in the literature. Release poteenciometria for WindowsMinitab: If ions can penetrate the boundary betweentwo phases, then an electrochemical equilibrium will be reached, in which different potentials in the two phases are formed. The measured signal is the sum of different potentials generated at all solid-solid, solid-liquid and liquid-liquid interfaces. Potentiometric titration applied to free fatty acid determination of edible oils and fats.

Equilibrium means that the transfer of ions from the membrane into solution is equal to the transfer from the solution to the membrane.

According the IUPAC recommendation the detection limit is defined by the cross-sectionof the two extrapolated linear parts od the ion-selective calibration curve. However, it should be pointed out that only at constant ionic strength a linearrelationship between the signal measured and the concentration of the analyte is maintained because of the clear cut relationship between ion activity and concentration, occurring in such condition. The selectivity coefficient Kxy has been introducedin the Nikolski-Eisenman equation.

Food Protection53 Negative values indicate a preference for the target ion relative to the interfering ion. The selectivity is one of the most important characteristics of an electrode, as it oftendetermines whether a reliable measurement in the sample is possible or not.