62
Spectral Contrast Theory
5
Figure 5-6 Effects of pH and Solvent Concentration
on the Absorbance Spectrum of
p
-Aminobenzoic Acid
Wavelength (nm)
200
220
240
260
280
300
320
340
pH 6.9
pH 5.1
pH 3.1
NH+
3
NH2
NH2
COOH
COOH
Effect of pH
p - Aminobenzoic Acid
COOH
200
220
240
260
280
300
320
340
Effect of Acetonitrile Concentration
p - Aminobenzoic Acid
COOH
NH2
2–10% Acetonitrile
Wavelength
Abs
o
rb
ance
Abso
rba
n
ce
nM
Effect of pH
p-Aminobenzoic Acid
pH 3.1
pH 5.1
pH 6.9
COO–
Effect of Acetonitrile Concentration
p-Aminobenzoic Acid