Waters 2475, Operator'S Manual, Page: 212 / 228

C-12 Solvent Considerations
Wavelength selection for chromophore detection
Certain functional groups found in most compounds absorb light selectively.
These groups, known as chromophores, and their behavior can be used to
categorize the detection of sample molecules. The following table lists some
common chromophores and their detection wavelengths (
λ
max), as well as the
molar absorptivity ( ε
max) of each group
1
. Use this information as a guide to
select the optimal operating wavelength for a particular analysis. Because of
the diversity possible within a given sample, scanning over a range of
wavelengths can be necessary to determine the best wavelength for a
particular analysis.
1. Willard, H. H. and others. Instrumental Methods of Analysis , 6th ed. Litton Educational Publishing,
Inc., 1981. Reprinted by permission of Wadsworth Publishing Co., Belmont, California, 94002.
Wavelength selection for chromophore detection
Chromophore
Chemical
Configuration
λ
max
(nm)
∈
max
(L/m/cm)
λ
max
(nm)
∈
max
(L/m/cm)
Ether —O— 185 1000
Thioether —S— 194 4600 215 1600
Amine —NH2 195 2800
Thiol —SH 195 1400
Disulfide —S—S— 194 5500 255 400
Bromide —Br 208 300
Iodide —I 260 400
Nitrile —C ≡ N 160 —
Acetylide —C ≡ C— 175–
180
6000
Sulfone —SO2 — 180 —
Oxime —NOH 190 5000
Ethylene —C=C— 190 8000
Ketone >C=O 195 1000 270–28
5
18–30
Thioketone >C=S 205 strong
Esters —COOR 205 50