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Elecrtoranlytical Technique- RajaRam 1
Electrochemical Methods of Analysis
Kuleswor, Viswa Vidylaya PathKathmandu, Nepal
Prof. Dr. Raja Ram Pradhananga
Elecrtoranlytical Technique- RajaRam 2
Introducction
Instrumental Techiques of AnalysisSpeoctroscopyElectrochemistryChromatography
Electrochemical TechniquesConductometryPotentiometryAmperometry and CoulometryVoltametry
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Electroanalytical Methods
• Analytical techniques based on the electrochemical measurements are often refer to as electrochemical methods of analysis or simply as Electroanalytical methods. This method of analysis involves the measurement of current, voltage or resistance alone or in combination. Sometime measurements are done as a function of time. Different Electroanalytical methods are given below.
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Electroanalytical methods
Interfacial Methods
Static Methods (I=0)
Dynamic Methods (I > 0)
Bulk Method
Conductometry
Electroanalytical Methods
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Static Method( I=0)
Potentiometry
pH-metry Ion-selective electrode
Potentiometric Titration
Electroanlytical Methods I
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Dynamic Method( I > 0 )
Controlled Potential
Voltametry Amperometry
Constant current
Electrogravimetry Coulometry
Electroanlaytical Methods II
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Basic Electrical Measurements
Resistance, R Ohms Law V = IRVoltage, VCurrent, I
These electrical properties are measured alone or in combination for analysis.
Additional electro-analytical techniques are possible if these electrical properties are measured as a function of time.
Principle of Electrochemical Method of Analysis
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Conductance Measurement
1/R is measured : Direct Conductance Analysis1/R versus volume of titrant: Conductometric titration
PotentiometryE is measured zero current,(I = 0)
i. pH- metryii. Ion selective potentiometry
E versus volume of titrant potentiometric titration
Voltametry: i versus E
Amperometric Titration: i versus volume of titrant
Electroctrogravimetry : Mass of material deposited is determined
Coulometry: Current x time (Coulomb)
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Svante Arrhenius Georg Ohm
Walter Nernst
M. Faraday
Pioneers of Electrochemical
Principles
Jaroslav Heyrovský
Nobel Prize in 1903
Nobel Prize in 1920 Nobel prize in 1959
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•
Syllabus
The following Electroanalytical techniques are included in Analytical Chemistry of Biochemistry 4th Semester of PU
1. Conductometry2. Potentiometry3. Amperometric Titration4. Coulometry Titration5. Polarography
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Main Branches of Electroanalytical Chemistry
1. Conductometry : Measure the conductance of a solution. Direct conductometry and conductometric titration.
2. Potentiometry: Measure the potential of electrochemical cells without drawing substantial current pH measurements, ion-selective electrodes, potentiometric
titration3. Amperometric Titration: Measures current as a function of
titrant.4. Coulometric Titration: Measures the quantity of charge
required to drive an electrolytic oxidation/reduction to completion
4 Polarography: Measures current as a function of applied potential in a dropping mercury electrode.
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Jaroslav Heyrovský
Nobel prize in 1959
For the development of polarographic technique of analysis
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M. Faraday
Faraday’s Laws of Electrolysis
Faraday Ist Law : The mass of the substance discharge at the electrode during electrolysis is directly proportional to the quantity of charge passed through the electrolyte.
w =zct
Faraday II : The masses of different substances discharged at the electrode by the same quantity of electricity are proportional to their chemical equivalent
w/E = constant
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