Principles Of Operation - Thermo Scientific Dionex ICS Series Operator's Manual

1.2

Principles of Operation

Photometric detection is based upon the absorption of monochromatic light. The
degree of absorption depends on the sample molecule, its concentration, the light's
path length in the sample, and the measurement wavelength.
Absorbance is defined as:
and is related to concentration by the empirical Lambert-Beer's Law:
where:
I Reference beam intensity
r
I Sample beam intensity
s
I Reference beam intensity with autozero
ro
I Sample beam intensity with autozero
so

Molar absorptivity coefficient of the analyte (L • mol
c Concentration (mol/L)
l Cell path length (cm)
UV-Vis spectroscopy allows you to detect the chromophores of analyte molecules
directly in the sample or to generate them indirectly by derivatization.
Appendix D provides a list of wavelengths for the absorption maxima of various
chromophores.
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1 • Introduction
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