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Y. Ozaki and Y. Morisawa
2.1.3 Advantages of NIR Spectroscopy
Now, let us discuss the advantages of NIR spectroscopy from the point of applications
[1–7]. First of all, NIR spectroscopy is a powerful non-destructive and in situ analysis
method. One can explore even inside of a material using NIR spectroscopy. Second, it
permits non-contact analysis, and analysis using an optical fiber. Third, it is possible
to apply NIR spectroscopy to samples in various states, shapes, and thickness. As for
the advantages of NIR spectroscopy for fundamental studies we discuss in Chap. 13.
One can discuss the advantages of NIR spectroscopy in comparison with IR
spectroscopy.
(1) NIR spectroscopy allows in situ analysis with a sample as it originally is. While
one can employ attenuated total reflection (ATR) or photoacoustic spectroscopy
(PAS) for in situ analysis in IR spectroscopy, there is no other choice than NIR
spectroscopy if one wishes to collect an absorption spectrum on the whole of an
apple or a human head. It is also suitable for nondestructive of thick samples.
(2) In general, NIR spectroscopy is more suitable in the analysis of aqueous solutions than IR spectroscopy since the intensity of water bands is much weaker in
the NIR spectrum than in the IR spectrum. ATR-IR spectroscopy permits one
to examine aqueous solutions, but NIR spectroscopy can probe those in more
various manners.
(3) A light-fiber probe can be set in a dangerous environment, and be remotely
manipulated. This is one of the reasons why NIR spectroscopy is suitable for
on-line analysis. IR Light-fibers are much less robust and more expensive.
(4) In NIR spectroscopy one can select a light path length very freely. In contrast,
IR spectroscopy usually requests a cell having a very short path length. NIR
spectroscopy allows one to use a 0.1-mm cell, a 1-cm cell, or even a 10-cm cell.
(5) Optical materials used in the NIR region are cheaper than those in the IR region.
One can use glass cells, for example.
2.1.4 Versatility of NIR Spectroscopy
NIR spectroscopy holds marked versatility in many aspects. First of all, it has huge
versatility in its applications [1–7]. NIR spectroscopy can be used in a laboratory,
a factory, a hospital, a field and a museum, at a building site, on a road and in the
atmosphere. It may be applied to solids, crystals, fibers, powders, liquids, solutions,
and gases. Almost all kinds of materials, from purified samples to bulk materials,
can be subjected to NIR measurements.
Another versatility in NIR spectroscopy is the versality in spectrometers and
instruments. (Chap. 9) In the IR region, most of the spectrometers employed are
FT spectrometers, while in the NIR region both FT spectrometers and dispersive
spectrometers are employed, and dispersive spectrometers with a CCD detector play
important roles in the short-wave NIR (SWNIR) region. NIR spectrometers with
Y. Ozaki and Y. Morisawa
2.1.3 Advantages of NIR Spectroscopy
Now, let us discuss the advantages of NIR spectroscopy from the point of applications
[1–7]. First of all, NIR spectroscopy is a powerful non-destructive and in situ analysis
method. One can explore even inside of a material using NIR spectroscopy. Second, it
permits non-contact analysis, and analysis using an optical fiber. Third, it is possible
to apply NIR spectroscopy to samples in various states, shapes, and thickness. As for
the advantages of NIR spectroscopy for fundamental studies we discuss in Chap. 13.
One can discuss the advantages of NIR spectroscopy in comparison with IR
spectroscopy.
(1) NIR spectroscopy allows in situ analysis with a sample as it originally is. While
one can employ attenuated total reflection (ATR) or photoacoustic spectroscopy
(PAS) for in situ analysis in IR spectroscopy, there is no other choice than NIR
spectroscopy if one wishes to collect an absorption spectrum on the whole of an
apple or a human head. It is also suitable for nondestructive of thick samples.
(2) In general, NIR spectroscopy is more suitable in the analysis of aqueous solutions than IR spectroscopy since the intensity of water bands is much weaker in
the NIR spectrum than in the IR spectrum. ATR-IR spectroscopy permits one
to examine aqueous solutions, but NIR spectroscopy can probe those in more
various manners.
(3) A light-fiber probe can be set in a dangerous environment, and be remotely
manipulated. This is one of the reasons why NIR spectroscopy is suitable for
on-line analysis. IR Light-fibers are much less robust and more expensive.
(4) In NIR spectroscopy one can select a light path length very freely. In contrast,
IR spectroscopy usually requests a cell having a very short path length. NIR
spectroscopy allows one to use a 0.1-mm cell, a 1-cm cell, or even a 10-cm cell.
(5) Optical materials used in the NIR region are cheaper than those in the IR region.
One can use glass cells, for example.
2.1.4 Versatility of NIR Spectroscopy
NIR spectroscopy holds marked versatility in many aspects. First of all, it has huge
versatility in its applications [1–7]. NIR spectroscopy can be used in a laboratory,
a factory, a hospital, a field and a museum, at a building site, on a road and in the
atmosphere. It may be applied to solids, crystals, fibers, powders, liquids, solutions,
and gases. Almost all kinds of materials, from purified samples to bulk materials,
can be subjected to NIR measurements.
Another versatility in NIR spectroscopy is the versality in spectrometers and
instruments. (Chap. 9) In the IR region, most of the spectrometers employed are
FT spectrometers, while in the NIR region both FT spectrometers and dispersive
spectrometers are employed, and dispersive spectrometers with a CCD detector play
important roles in the short-wave NIR (SWNIR) region. NIR spectrometers with