The instrumentation used to perform potentiometry is straightforward, consisting of an indicator electrode, a reference electrode, and a potential measuring device. Applications of potentiometry involve the use of an electrochemical cell consisting of a reference electrode of constant potential and an indicator electrode that responds to the analyte studied and sample composition. A good reference electrode for potentiometric mea surements must. Basic overview of the working principle of a potentiostat. Potentiometric titrations provide more reliable data than data from titrations that use chemical indicators and. This socalled reference electrode allows control of the. Potentiometry and ion selective electrode ch 141 to 146 reference electrodes indicator. The reference electrolyte and the bridge electrolyte can. Potentiometric titration is a technique similar to direct titration of a redox reaction. Pdf solidstate reference electrodes for potentiometric. In most electrochemical measurements it is necessary to keep one of the electrodes in an electrochemical cell at a constant potential. The high stability of the reference electrode potential is usually reached by employing a. Potentiometric measurement system consists of two electrodes called reference and indicator electrode, potentiometer and a solution of analyte figure 2. That is, the potential of the electrode will change significantly from its equilibrium potential with the application of even a small current density.
In conjunction with this reference is the indicator or working electrode, whose response depends upon the analyte concentration. View notes lecture 8 potentiometry, electrode from chem 215 at simon fraser university. The salt bridge is used to prevent the interference of the analyte solution with that of reference solution. Environmental protection agency office of water office of science and technology engineering and analysis division 4303 1200 pennsylvania ave. Potentiometric titrations potentiometric titrations involves the measurement of the potential of a suitable indicator electrode with respect to a reference electrode as a function of titrant volume. The reaction at the ag indicator electrode is the calomel reference halfcell reaction is the reference potential e. For example, ph, ion selective electrodes, blood gas analysis o 2, co 2, etc. Potentiometry is mainly used to determine the potential or the electromotive force of a sample solution. A discussion of potentiometry and the various electrodes we use in analytical chemistry. A reference electrode is an electrode which has a stable and wellknown electrode potential. The sensing part of the electrode is usually made as an ionspecific membrane, and coupled to a external reference electrode combination electrode.
In potentiometry, those two electrodes are generally called the indicator electrode and the reference electrode. The ph electrode and potentiometric titrations in this experiment you will investigate the nernstian response of a ph electrode, perform potentiometric titrations, investigate the acidbase properties of the bicarbonate buffer system. For a long time, considerable efforts have been made to. Alternative strategy for manufacturing of allsolidstate reference. One of the electrodes is a reference electrode, whose electrode potential is known. Importance in environmental and medical applications. Pdf solidstate reference electrodes for potentiometric sensors. Wearable potentiometric sensors for medical applications mdpi. Ideal reference reversible and obeys nernst law exhibits stable potential over time returns to original potential in presence of small currents not sensitive to temperature changes chem 4631. Learn vocabulary, terms, and more with flashcards, games, and other study tools.
The indicator electrode possesses some characteristic that allows it to selectively respond to changes in the activity of the analyte being measured. This simplicity makes potentiometry an inexpensive technique compared to atomic spectroscopy or ion chromatography. The ph electrode and potentiometric titrations in this experiment you will investigate the nernstian response of a ph electrode, perform potentiometric titrations, investigate the acidbase properties of the bicarbonate buffer system, and determine the pka values of lhistidine. Apr 01, 2018 electrode potential, cell, half cell, standard hydrogen electrode, hydrogen half cell, zn half cell, cu half cell, chlorine half cell, li half cell, electrochemical series, electrode potential of. Silver silver chloride electrode the silversilver chloride reference electrode is a widely used reference electrode because it is simple, inexpensive, very stable and nontoxic.
Properties of umass boston reference electrode reversible and obey nernst equation exhibit a potential that is constant with time return to its original potential after. This is from chapter 14 in quantitative chemical analysis 8e by harris. Mar 10, 2015 the reference electrode is the electrode which contains of its own potential value and it is stable when dipped into sample solution. Classification of electrode types electrodes and potentiometry relating concentration to electrode potential class 1.
Electrodes and potentiometry reference electrodes maintains a fixed reference potential indicator electrodes responds to analyte activity solution. Indicator electrode an overview sciencedirect topics. Silversilver chloride reference electrode with doublejunction system, installation length 10 cm. The standard hydrogen electrode plays the role of a basic. In many electrodes designed for potentiometry, the reference half cell is contained within the body of the sensing electrode.
Electrode potential, cell, half cell, standard hydrogen electrode, hydrogen half cell, zn half cell, cu half cell, chlorine half cell, li half cell, electrochemical series, electrode potential of. Principal purposes of the study are a to understand quantitative relationships between electrode potential and concentration and b to use that information to understand how absolute and relative. No electrode responds exclusively to one kind of ion. Ammonian in water and biosolids by ionselective electrode potentiometry with preliminary distillation draft january 2001 u.
To do this, two electrodes are used, an indicator electrode the glass electrode and metal ion. Electrodes and potetiometry minnesota state university. Potentiometry and types of electrodes flashcards quizlet. Chem 321 lecture 16 potentiometry 1022 student learning objectives in lab you will use an ionselective electrode to determine the amount of fluoride in an unknown solution. This socalled reference electrode allows control of the potential of a working electrode e. The unknown solution is converted into a halfcell by adding an electrode e. Potentiometry uses electrodes to measure voltages which are related. Jul 22, 2015 reference electrodes a reference is an electrode that has the halfcell potential known, constant, and completely insensitive to the composition of the solution under study. Common reference electrodes used in potentiometry i calomel electrodes hg in contact with hg 2 cl 2. Contact to the measurement cell is made through a porous glass frit or fiber which allows the movement of ions, but not the bulk solution. Common reference electrodes used in potentiometry i calomel electrodes hg in contact with hg. Potentiometry potential is measured under the conditions of no current flow the measured potential is proportional to the concentration of some component of the analyte the potential that develops in the electrochemical cell is the.
This arrangement is referred to as a combination electrode. In this approach, as with ph measurements, the potential of an electrochemical cell is associated with the concentration actually activity of a particular. The reference electrode has to be placed downstream of the indicator electrode in order to avoid interferences at the indicator electrode due to slow diffusion of the internal electrolyte from the reference electrode. The reason for this behavior is that the electrode. Lecture 8 potentiometry, electrode potentiometry and. Introduction this experiment introduces the directmeasurement approach to potentiometry. Reference electrode electrochemistry chemistry class 12. The high stability of the electrode potential is usually reached by employing a redox system with constant buffered or saturated concentrations of each participant of the redox reaction. Ionselective electrodes determination of the sodium monofluorophosphate content of a toothpaste sample using a fluoride ionselective electrode.
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