1. UV-Vis Spectroscopy

2. HPLC: Peak Area vs Detector setting
UV-Vis Spectroscopy
HPLC: Peak Area vs Detector setting
Excedrin ES
250 mg aspirin; 250 mg acetaminophen; 65 mg caffeine
Detector set at 240 nm
Area %
Aspirin %
Acetaminophen 50.0%
Caffeine %
Detector set at 254 nm
Area %
Aspirin %
Acetaminophen 81.9%
Caffeine %
Detector set
at 280 nm
Area %
Aspirin %
Acetaminophen 39.3%
Caffeine %

3. UV-Vis Spectroscopy: lmax
240 nm
Acetaminophen (1.6 x 10-3 g/L)
lmax = 248 nm, Abs. = 0.61
254 nm
280 nm
Aspirin
(1.6 x 10-3 g/L)
lmax = 296 nm, Abs. = 0.18
Caffeine
(1.6 x 10-3 g/L)
lmax = 272 nm, Abs. = 0.34

4. UV-Vis Spectroscopy: lmax and molar absorbtivity (e)
Acetaminophen (1.6 x 10-3 g/L)
lmax = 248 nm, Abs. = 0.61
Caffeine
(1.6 x 10-3 g/L)
lmax = 272 nm, Abs. = 0.34

5. UV-Vis Spectroscopy: Chromophores
/UV-Vis/spectrum.htm

6. Methyl bromide Methyl Iodide
UV-Vis: Chromophores
Chromo-phore
Example
Excitation
λmax, nm ε
Solvent
C=C
Ethene
π  __>   π*
171
15,000
hexane
C≡C
1-Hexyne
180
10,000
C=O
Ethanal
n  __>  π* π  __>  π*
15 10,000
hexane hexane
N=O
Nitro-methane
17 5,000
ethanol ethanol
C-X  
X=Br
X=I
Methyl bromide Methyl Iodide
n  __>  σ* n  __>  σ*

7. UV-Vis Spectroscopy: Chromophores
Table 7.3, p 362 Intro to Spectroscopy, 3rd ed., Pavia et al.

8. UV-Vis Spectroscopy: Solvents
p Intro to Spectroscopy, 3rd ed., Pavia et al.

9. UV-Vis Spectroscopy: CONJUGATION
p 363 Intro to Spectroscopy, 3rd ed., Pavia et al.
Spectrpy/UV-Vis/spectrum.htm

10. UV-Vis Spectroscopy: Aromatic Compounds
p Intro to Spectroscopy, 3rd ed., Pavia et al.

11. UV-Vis: Aromatics
p 379 Intro to Spectroscopy, 3rd ed., Pavia et al.

12. UV-Vis: Acid/Base
p 377 Intro to Spectroscopy, 3rd ed., Pavia et al.

13. UV-Vis: Acid/Base Terminology for Absorption Shifts Nature of Shift
Descriptive Term
To Longer Wavelength
Bathochromic
To Shorter Wavelength
Hypsochromic
To Greater Absorbance
Hyperchromic
To Lower Absorbance
Hypochromic

14. UV-Vis: Acid/Base

15. UV-Vis: Empirical Rules
p 380 Intro to Spectroscopy, 3rd ed., Pavia et al.

16. UV-Vis: Empirical Rules
p 380 Intro to Spectroscopy, 3rd ed., Pavia et al.