Appendix C Spectroscopy Background
Photometric Linearity
AA003700-01 rev. G. 2.0
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Appendix C Spectroscopy Background
Photometric Linearity
Introduction
Beer’s law relates the absorbance intensity of spectral bands to the concentration of
the analyte and the pathlength of the light beam through the sample. In an FTIR
Absorbance is not measured directly, but is derived via the negative logarithm of the
ratio of sample spectrum divided by background spectrum.
Figure C- 1
shows a
series of six absorbance spectra of pure Toluene recorded with a variable
path length liquid cell. The pathlength settings are 1000
μ
m, 750
μ
m, 500
μ
m,
250 u
μ
m, 100
μ
m and 33
μ
m for highest to lowest absorbance intensity.
Figure C- 1. Series of toluene spectra
