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6.1 Introduction

polarogaphy

liquid electrodes

woking electrodes

solid electrodes

voltammetry

6.2 Foundamentals of general polarography

6.2.1 The introduction of the classical

polarography

Design Fig6.2-1

e.g. Polarograms ( i vs E relationships ) of

Cd2 Fig6.2-2

The half-wave potential is indepent of the

concentration

The specification of polarograms determination

6.2.2 the form of polarogram

The polarogram has three current regions

The residual current (ir) region

Diffusion current (id) region

Limiting current (il) region

6.2.3 The specification of electrode

Polarization electrode

Unpolarization electrode

The advantages of the dropping mercury

electrode (DME)

6.3 Diffusion current equation

6.3.1 Ilkovic diffusion current equation

id k n D1/2 m2/3 t1/2 Cox

6.3.2 The factors determining the diffusion

current

The analyte concentration

The characteristics of the capillary

The effect of dropping mercury potential

Temperature effect

6.4 Factors affecting the shape of the polargram

The residual current Fig6.4-1 Fig6.4-2

The current maxima Fig6.4-3

The presence of oxygen Fig6.4-4

6.5 The quantitative analytical method of

polarography

6.5.1 The determination of diffusion current

Parallel method Fig6.5-1

Thritangential method Fig6.5-2

6.5.2 The quantitative method of polargraphy

Directive comparative method

Working curve Fig6.5-3

Standard addition method Fig6.5-4

6.6 Introduction about new polarography

6.6.1 Polaro-catalysing wave

6.6.2 Stripping analysis method

6.6.3 Linear sweep(dc) oscillo- polarography

Basic line Fig6.6-1 Fig6.6-2

6.6.4 Circular voltammetry

Fundamental Fig6.6-3

Application Fig6.6-4

It is special electrolytic design which

consists of

a. Electrolytic cell

b. Voltmeter V

c. Ampere meter

Its specialties show

a. Large areas of reference electrode

b. Small areas of working electrode

c. The infinite dilution

As the half-wave potential is independent of

solution analyte concentration and dependant

primary on the nature of analyte.

It can be used for the identification of analyte

species taking part in the electrode reaction.

In general, they are ascribed to the

convection of the solution layer in the vicinity

of the working electrode which is induced by the

inhomogeneous charge distribution in the dropping

Hg electrode.

Elimination

The current maxima can be supppressed by the

addition of polarographically inactive

surfactants, such as gelation, methyl red or

other dyes to obtain the desired effect.

Elimination methods

? In neutral or alkaline media by Na2SO3 solution

? In solution of all pH by N2 or Ar or H2 etc.

? In acid solution by ascorbic acid

Then

The principles of qualitative quantitative and

analysis Fig.6.6

? The basis for quantitative analysis

ip Kn3/2D1/2V1/2AC

? The basis for qualitative analysis

Peak potential is only decided by the

properties of reducing material under certain

condition (temperature, the fixed bottom solution

).

Working electrode, static electrode such as

? Suspending electrode

? Stationary electrode

Which was mainly used to study the mechanism

of electrode process, such as

The determination of its reverse

The distance between two peaks is farther,

the more irreverent it is.