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Electrochemical Methods of Analysis

Kuleswor, Viswa Vidylaya PathKathmandu, Nepal

Prof. Dr. Raja Ram Pradhananga

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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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