Harris Quantitative Analysis, Instrumental Analysis

1. Chapter 5Chapter 5
Ultraviolet and VisibleUltraviolet and Visible
SpectrophotometrySpectrophotometry
5.1. Concepts of UV-Vis.UV-Vis.Spectrophotometry
5.2. UV-Vis.UV-Vis. Spectrophotometer
5.3. Analytical Methods

2. 5.1.
Concepts of UV-Vis.UV-Vis. Spectrophotometry
1. Molecular absorption and Fluorescence

3. 2. Lambert-Beer’s Law
(1)Transmittance T:
KbC
P
P
eT −
== 0
(5.1)

4. (2) Absorbance:
bCK
p
p
TA 4343.0lglg 0
=





=−=
(3) Molar absorptivity ε
When: the unit of b is in cm , C in mol/L,
molar absorptivity ε is:
σε BKv
20
1087.04343.0 ×==
B:transition probability, σ: effective area of
molecular
(5.2)
(5.3)

5. 5.2.5.2.
UV-Vis. SpectrophotometerUV-Vis. Spectrophotometer
AA SpectrophotometerSpectrophotometer

6. Double beanDouble bean
UV-Vis. SpectrophotometerUV-Vis. Spectrophotometer

7. 5.3.
Analytical Methods
1. Qualitative Analysis
2. Quantitative Analysis
3. Dual wavelength Spectrophotometry
4. Differential Spectrophotometry
5. Derivative Spectra

8. 1. Qualitative Analysis
Organic Compound⑴
Chromophor
e
λmax(nm) ε(mol-1
.cm-
1
)
Transition Type
R3 C—N — 200 3000 n→σ*
R3 C—S — 200 2000 n→σ*
—N=N — 340 10 n→ π *
—S —S — 250-330 1000 n→σ*
R2 C=S 5 0 0,2 4 0 10,9000 n→ π *
R2 C=O 2 8 0,1 9 0 20,2000 n→σ*, n→ π *
—COOR 205,165 50,4000 n→ π *,π → π*

9. ⑵Inorganic Compound
Ion n3d,e λmax(nm) Ion n3d,e λmax(nm)
Sc2+
0 ------ Zn2+
10 ------
Ti(H2O)6
3+
1 492.6 Cu+
10 ------
VO2+
1 625 Cu(H2O)6
2+
9 592,794
Cr (H2O)6
3+
2 407,575 Ni(H2O)6
2+
8 395,650,740
V (H2O)6
2+
3 557 Co(H2O)6
2+
7 516,541,625
Cr (H2O)6
2+
3 709 Fe(H2O)6
3+
5 411,540,794
Mn (H2O)6
3+
4 476 Mn(H2O)6
2+
4 402,435,532

11. 3. Double wavelength Spectrophotometry

12. Two-component analysis with double wavelength
AC,520 = AC,540
AB+C,520 = AB,520 + AC,520
AB+C,540 = AB,540 + AC,540
∆A = AB+C,520 - AB+C,540
= AB,520 - AB,540

13. 4. Differential Spectrophotometry
1,2,
1,
,
ss
sx
xd
TT
TT
T
−
−
=
1,1,,2,, ssxdsxdx TTTTTT +−=
(5.4)
(5.5)

14. ⑴⑴when Twhen TSS,,11=0,T=0,TSS,,22=100%=100%
⑵⑵when Twhen TSS,,11=0,T=0,TSS,,22<100%<100%
⑶⑶when Twhen TSS,,11>0>0
xxdx lcAA ⋅== ε,
xsxdx lcAAA ⋅=+= ε2,,
x
ssxdsxd
xx
lc
TTTTT
TA
⋅=
+−−=
−=
ε
)lg(
lg
1,1,,2,,
(5.6)
(5.7)
(5.8)

15. 5. Derivative Spectra5. Derivative Spectra

16. 5.4
Molecular Fluorescence Spectrometer