Ocean Optics DTS - Manual (Page 50)

Chapter 6
6-4 Polychromix DTS TM Near-Infrared Spectrometer
Operator’s Manual
Document Number 04-91-0201-00 Rev A
Table 6-1: Sample Related Issues
Problem Cause Solution
The absorbance is
weak or % T is very
high (noisy spectrum) The sample is too dilute
or too thin Prepare a more
concentrated sample
Use Spectrum
Averaging to reduce
noise (Section 6.4)
The absorbance is too
strong or % T is near
zero The sample is too
concentrated or thick Dilute the sample or
use a thinner cuvette
Intensity of peaks
change Sample Decomposition Use a thermostated
cuvette holder
Spectrum does not
compare to spectrum in
another solvent Interaction between
sample and solvent Replace solvent
6.2.6 Quantitative Measurements
The transmission (T) of a sample is defined by equation 6-1.
T = P/P
o
6-1
where: P is the power of the light that is transmitted by the sample
P
o
is the power of the light incident on the sample
The absorbance (A) of a sample is the logarithm (base 10) of the reciprocal of
the transmittance (equation 6-2).
A = -log T = log (1/T) 6-2
Beer’s Law (equation 6-3), can be used to determine the concentration of the
compound of interest.
A = e x c x l 6-3
where: A is the absorbance
e is the molar absorbance coefficient, which is a constant for a
compound in a given solvent at a given temperature
c is the concentration of the compound
l is the path length.