Waters 2489, Overview And Maintenance Manual

Page: 149 / 150

June 11, 2015, 715004752 Rev. A
Page 149
C.8.3 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
(
λ
max
), as well as the molar absorptivity (
ε
max
) of each group. 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
may be necessary to determine the best wavelength for a particular analysis.
Table C–4: Electronic absorption bands of representative chromophores*:
Chromophore Chemical
configuration
λ
max
(nm)
∈
max
(L/m/cm
)
λ
max
(nm)
∈
max
(L/m/c
m)
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
Azido >C=N— 190 5000
Ethylene —C=C— 190 8000
Ketone >C=O 195 1000 270-285 18-30
Thioketone >C=S 205 strong
Esters —COOR 205 50
Aldehyde —CHO 210 strong 280-300 11-18
Carboxyl —COOH 200-210 50-70
Sulfoxide >S
→
O 210 1500
Nitro —NO2 210 strong
Nitrile —ONO 220-230 1000-2000 300-400 10
Azo —N=N— 285-400 3-25
Nitroso —N=O 302 100
Nitrate —ONO2 270
(shoulde
r)
12