Potentiometric titration
Oxford Dictionary of Biochemistry:
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potentiometric titration
or (sometimes) electrometric titration
titration in which an electrode reversible to one of the ionic components of the analyte or titrant is immersed in the analyte solution and the electric potential of the electrode (relative to that of an inert reference electrode) is measured during addition of titrant. Because the potential of an electrode is a logarithmic function of the activity of the ion to which the electrode is reversible, an abrupt change in its potential is observable as an equivalence point is approached.
titration in which an electrode reversible to one of the ionic components of the analyte or titrant is immersed in the analyte solution and the electric potential of the electrode (relative to that of an inert reference electrode) is measured during addition of titrant. Because the potential of an electrode is a logarithmic function of the activity of the ion to which the electrode is reversible, an abrupt change in its potential is observable as an equivalence point is approached.
| potentiometer, potentiate, potential gradient | |
| potocytosis, pound, powder pattern |
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Potentiometric titration
Potentiometric titration is a technique similar to direct titration of a redox reaction. No indicator is used, instead the potential across the analyte, typically an electrolyte solution is measured. To do this, two electrodes are used, an indicator electrode and a reference electrode. The indicator electrode forms an electrochemical half cell with the interested ions in the test solution. The reference electrode forms the other half cell, holding a consistent electrical potential. The overall electric potential is calculated as Ecell = Eind - Eref + Esol. Esol is the potential drop over the test solution between the two electrodes. Ecell is recorded at intervals as the titrant is added. A graph of potential against volume added can be drawn and the end point of the reaction is half way between the jump in voltage.
Ecell depends on the concentration of the interested ions with which the indicator electrode is in contact. For example, the electrode reaction may be
Mn++ne------>M
As the concentration of Mn+ changes,the Ecell changes correspondingly. Thus the potentiometric titration involve measurement of Ecell with the addition of titrant. types of potentiometric titration: acid-base titration (total alkalinity and total acidity), redox titration (HI/HY and cerate), precipitation titration (halides), and complexometric titration (free EDTA and Antical #5).
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Oxford Dictionary of Biochemistry
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