Waters 2998 Operator's Manual page 113

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 table below lists some common chromophores, and their detection
wavelengths (
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 may be necessary to determine the best
wavelength for a particular analysis.
Electronic absorption bands of representative chromophores *
Chromophore
Ether
Thioether
Amine
Thiol
Disulfide
Bromide
Iodide
Nitrile
Acetylide
Sulfone
Oxime
Azido
Ethylene
Ketone
Thioketone
Esters
Aldehyde
Carboxyl
Sulfoxide
), as well as the molar absorptivity (ε
λ
max
Chemical
Configuration
—O—
—S—
—NH 2
—SH
—S—S—
—Br
—I
—C≡N
—C≡C—
—SO 2 —
—NOH
>C=N—
—C=C—
>C=O
>C=S
—COOR
—CHO
—COOH
>S—O
λ ∈
max max
(nm) (L/m/cm)
185 1000
194 4600
195 2800
195 1400
194 5500
208 300
260 400
160 —
175-180 6000
180 —
190 5000
190 5000
190 8000
195 1000
205 strong
205 50
210 strong
200-210 50-70
210 1500
Wavelength selection
) of each group. Use
max
λ ∈
max max
(nm) (L/m/cm)
215 1600
255 400
270-285 18-30
280-300 11-18
C-13