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Y. Ozaki et al.
Fig. 4.2 A NIR spectra in
the 7500–5500 cm −1 region
of water-methanol mixtures
with a methanol
concentration of 0–100 wt%
at increments of 5 wt% at
25 °C. B a An enlargement
of the 6000–5700 cm −1
region of the NIR spectra
shown in A and B, b the
second derivative of the
spectra in a. Reproduced
from Ref. [10] with
permission
into many bands which show clear concentration-dependent variations. Derivative
methods will be explained in more detail in Chap. 4.3.2.
(3) Calculation of difference spectra
Calculation of difference spectra is also useful to unravel overlapping bands and to
find out a weak feature hidden by a strong band [1, 2, 5, 7]. The difference spectrum between a spectrum of sample a and that of sample b can be calculated by
Y. Ozaki et al.
Fig. 4.2 A NIR spectra in
the 7500–5500 cm −1 region
of water-methanol mixtures
with a methanol
concentration of 0–100 wt%
at increments of 5 wt% at
25 °C. B a An enlargement
of the 6000–5700 cm −1
region of the NIR spectra
shown in A and B, b the
second derivative of the
spectra in a. Reproduced
from Ref. [10] with
permission
into many bands which show clear concentration-dependent variations. Derivative
methods will be explained in more detail in Chap. 4.3.2.
(3) Calculation of difference spectra
Calculation of difference spectra is also useful to unravel overlapping bands and to
find out a weak feature hidden by a strong band [1, 2, 5, 7]. The difference spectrum between a spectrum of sample a and that of sample b can be calculated by