Chapter 4
Spectral Analysis in the NIR
Spectroscopy
Yukihiro Ozaki, Shigeaki Morita, and Yusuke Morisawa
Abstract This chapter is concerned with the introduction to spectral analysis in the
NIR spectroscopy. It consists of two major parts, conventional spectral analysis and
spectra pretreatments. In the former, various conventional spectral analysis methods
such as group frequency analysis, derivative spectra, difference spectra, spectral
analysis based on perturbation, comparison of a NIR spectrum with the corresponding
IR spectrum, and isotope exchange experiments are explained. In the latter part
smoothing, derivative methods, multiplicative scatter correction (MSC), standard
normal variate (SNV), centering methods, and normalization are described.
Keywords Spectral analysis · Chemometrics · Group frequency · Derivative ·
Difference spectra · Spectral pretreatment · Baseline correction noise
4.1 Introduction to Spectral Analysis in the NIR Region
As described partly in Chaps. 1 and 2 there are various kinds and various types of
NIR spectra [1–7]. First of all, NIR spectra can be divided into electronic spectra
and vibrational spectra. However, in this chapter, we treat only vibrational spectra
of solids and liquids. Compared with IR spectroscopy diversity of the types of NIR
spectra is quite large because NIR spectroscopy is concerned with so many kinds
of materials from pure samples such as pure liquids, solutions, and crystals to bulk
materials including raw materials, industrial products, and natural products. To look
at the diversity of NIR spectra let us compare the spectrum of methanol (0.005 M,
in CCl 4 ; see Fig. 2.3) with that of flour (Fig. 4.1). The former is rather simple
Y. Ozaki (B)
School of Science and Technology, Kwansei Gakuin University, Sanda, Japan
e-mail: yukiz89016@gmail.com
Toyota Physical and Chemical Research Institute, Nagakute, Japan
S. Morita
Faculty of Engineering, Osaka Electro-Communication University, Neyagawa, Japan
Y. Morisawa
School of Science and Engineering, Kindai University, Higashi-Osaka, Japan
© Springer Nature Singapore Pte Ltd. 2021
Y. Ozaki et al. (eds.), Near-Infrared Spectroscopy,
https://doi.org/10.1007/978-981-15-8648-4_4
63
Spectral Analysis in the NIR
Spectroscopy
Yukihiro Ozaki, Shigeaki Morita, and Yusuke Morisawa
Abstract This chapter is concerned with the introduction to spectral analysis in the
NIR spectroscopy. It consists of two major parts, conventional spectral analysis and
spectra pretreatments. In the former, various conventional spectral analysis methods
such as group frequency analysis, derivative spectra, difference spectra, spectral
analysis based on perturbation, comparison of a NIR spectrum with the corresponding
IR spectrum, and isotope exchange experiments are explained. In the latter part
smoothing, derivative methods, multiplicative scatter correction (MSC), standard
normal variate (SNV), centering methods, and normalization are described.
Keywords Spectral analysis · Chemometrics · Group frequency · Derivative ·
Difference spectra · Spectral pretreatment · Baseline correction noise
4.1 Introduction to Spectral Analysis in the NIR Region
As described partly in Chaps. 1 and 2 there are various kinds and various types of
NIR spectra [1–7]. First of all, NIR spectra can be divided into electronic spectra
and vibrational spectra. However, in this chapter, we treat only vibrational spectra
of solids and liquids. Compared with IR spectroscopy diversity of the types of NIR
spectra is quite large because NIR spectroscopy is concerned with so many kinds
of materials from pure samples such as pure liquids, solutions, and crystals to bulk
materials including raw materials, industrial products, and natural products. To look
at the diversity of NIR spectra let us compare the spectrum of methanol (0.005 M,
in CCl 4 ; see Fig. 2.3) with that of flour (Fig. 4.1). The former is rather simple
Y. Ozaki (B)
School of Science and Technology, Kwansei Gakuin University, Sanda, Japan
e-mail: yukiz89016@gmail.com
Toyota Physical and Chemical Research Institute, Nagakute, Japan
S. Morita
Faculty of Engineering, Osaka Electro-Communication University, Neyagawa, Japan
Y. Morisawa
School of Science and Engineering, Kindai University, Higashi-Osaka, Japan
© Springer Nature Singapore Pte Ltd. 2021
Y. Ozaki et al. (eds.), Near-Infrared Spectroscopy,
https://doi.org/10.1007/978-981-15-8648-4_4
63