1. polaro- and voltamanalytical methods
Chapter 6
6.1 Introduction
polarogaphy
liquid electrodes
woking electrodes
solid electrodes
voltammetry

2. 6.2.1 The introduction of the classical polarography
6.2 Foundamentals of general polarography
The introduction of the classical polarography
• Design Fig6.2-1
e.g. Polarograms ( i vs E relationships ) of Cd2+ Fig6.2-2

3. • The half-wave potential is indepent of the concentration
• The specification of polarograms determination

4. The polarogram has three current regions:
the form of polarogram
The polarogram has three current regions:
• The residual current (ir) region
• Diffusion current (id) region
• Limiting current (il) region

5. 6.2.3 The specification of electrode
• Polarization electrode
• Unpolarization electrode
• The advantages of the dropping mercury electrode (DME)

6. 6.3 Diffusion current equation
6.3.1 Ilkovic diffusion current equation
id = k •n •D1/2 •m2/3 •t1/2 •Cox

7. 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

8. • The residual current Fig6.4-1 Fig6.4-2
6.4 Factors affecting the shape of the polargram
• The residual current Fig Fig6.4-2
• The current maxima Fig6.4-3
• The presence of oxygen Fig6.4-4

9. 6.5 The quantitative analytical method of polarography
The determination of diffusion current
• Parallel method Fig6.5-1
• Thritangential method Fig6.5-2

10. 6.5.2 The quantitative method of polargraphy
• Directive comparative method
• Working curve Fig6.5-3
• Standard addition method Fig6.5-4

11. 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 Fig Fig6.6-2

12. 6.6.4 Circular voltammetry • Fundamental Fig6.6-3
• Application Fig6.6-4

13. It is special electrolytic design which consists of:
a. Electrolytic cell
b. Voltmeter V
c. Ampere meter

14. Its specialties show: a. Large areas of reference electrode
b. Small areas of working electrode
c. The infinite dilution

15. As the half-wave potential is independent of solution analyte concentration and dependant primary on the nature of analyte.

16. It can be used for the identification of analyte species taking part in the electrode reaction.

17. 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.

18. 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.

19. 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

20. h = KCx
H = K
VCx + VsCs
V + Vs
Then
Cx =
CxVsh
H (V + Vs) - hV

21. The principles of qualitative quantitative and analysis Fig.6.6
 The basis for quantitative analysis:
ip = Kn3/2D1/2V1/2AC

22.  The basis for qualitative analysis:
Peak potential is only decided by the properties of reducing material under certain condition (temperature, the fixed bottom solution ).

23. Working electrode, static electrode such as:
 Suspending electrode
 Stationary electrode

24. Which was mainly used to study the mechanism of electrode process, such as:

25. The determination of its reverse:
(mv)
Ep = Epa – Epc = 56 n

26. The distance between two peaks is farther, the more irreverent it is.
Ep > (mv), 56 n
ipa
ipc = 1 ,
The distance between two peaks is farther, the more irreverent it is.