64
Y. Ozaki et al.
Fig. 4.1 A NIR spectrum of
flour. Measured by A.
Ikehata
Wavelength /nm
log(1/R)
Wavenumber /cm
-1
500
1000
1500
2000
2500
0
0.2
0.4
0.6
10000
4000
6000
8000
20000
although several bands are overlapped in the 4500–4000 cm
−1 region. It has very
little baseline change. On the other hand, the spectrum of flour consists mainly of
the spectra of water, starch, and proteins. Bands are broad, and its baseline increases
with the increase in the wavelength. Like this NIR spectra show significant diversity
depending on samples and conditions. Therefore, spectral analysis methods are also
diverse in NIR spectroscopy [1–3]. In other words, one must select the best spectral analysis method for a target. The spectral analysis methods must change with
samples, sample conditions, measurement methods, and the purpose of analysis. The
purpose of analysis is also wide spread varies from quantitative analysis, qualitative
analysis, and sample identification to studies of molecular structure and chemical
reaction. Therefore, when one selects a spectral analysis method, one must consider
the purpose of analysis. For many purposes, chemometrics is very useful but for some
purposes it is almost meaningful. In this chapter, general introduction to the spectral analysis methods and spectral pretreatments for NIR spectra are outlined. The
detailed explanations of representative spectral analysis methods such as chemometrics (Chap. 7), two-dimensional correlation spectroscopy (2D-COS, Chap. 6), and
quantum chemical calculations (Chap. 5) will be given in each chapter and session.
As in the cases of IR and Raman spectroscopy, band assignments are always
the base for spectral analysis of NIR spectroscopy. However, the assignments are
generally not straightforward since a number of bands originating from overtones
and combinations overlap each other. In some cases, bands arising from combinations
including combinations of overtones appear; for such cases, it is very difficult to make
accurate band assignment. In NIR spectroscopy detailed band assignments are often
not necessary, but even in such cases, one should know from which functional group
a band arises.
Spectral analysis methods in NIR spectroscopy can be divided into conventional
spectral analysis method, chemometrics [3], quantum chemical calculation [5, 8], and
2D-COS [1]. The conventional spectral analysis methods are, more or less, common
among NIR, IR, Raman, and Terahertz/far-IR(FIR) spectroscopy. One must know
Y. Ozaki et al.
Fig. 4.1 A NIR spectrum of
flour. Measured by A.
Ikehata
Wavelength /nm
log(1/R)
Wavenumber /cm
-1
500
1000
1500
2000
2500
0
0.2
0.4
0.6
10000
4000
6000
8000
20000
although several bands are overlapped in the 4500–4000 cm
−1 region. It has very
little baseline change. On the other hand, the spectrum of flour consists mainly of
the spectra of water, starch, and proteins. Bands are broad, and its baseline increases
with the increase in the wavelength. Like this NIR spectra show significant diversity
depending on samples and conditions. Therefore, spectral analysis methods are also
diverse in NIR spectroscopy [1–3]. In other words, one must select the best spectral analysis method for a target. The spectral analysis methods must change with
samples, sample conditions, measurement methods, and the purpose of analysis. The
purpose of analysis is also wide spread varies from quantitative analysis, qualitative
analysis, and sample identification to studies of molecular structure and chemical
reaction. Therefore, when one selects a spectral analysis method, one must consider
the purpose of analysis. For many purposes, chemometrics is very useful but for some
purposes it is almost meaningful. In this chapter, general introduction to the spectral analysis methods and spectral pretreatments for NIR spectra are outlined. The
detailed explanations of representative spectral analysis methods such as chemometrics (Chap. 7), two-dimensional correlation spectroscopy (2D-COS, Chap. 6), and
quantum chemical calculations (Chap. 5) will be given in each chapter and session.
As in the cases of IR and Raman spectroscopy, band assignments are always
the base for spectral analysis of NIR spectroscopy. However, the assignments are
generally not straightforward since a number of bands originating from overtones
and combinations overlap each other. In some cases, bands arising from combinations
including combinations of overtones appear; for such cases, it is very difficult to make
accurate band assignment. In NIR spectroscopy detailed band assignments are often
not necessary, but even in such cases, one should know from which functional group
a band arises.
Spectral analysis methods in NIR spectroscopy can be divided into conventional
spectral analysis method, chemometrics [3], quantum chemical calculation [5, 8], and
2D-COS [1]. The conventional spectral analysis methods are, more or less, common
among NIR, IR, Raman, and Terahertz/far-IR(FIR) spectroscopy. One must know