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Chapter 10
Spectroscopic Methods
Chapter Overview
Section 10A
Section 10B
Section 10C
Section 10D
Section 10E
Section 10F
Section 10G
Section 10H
Section 10I
Section 10J
Section 10K
Section 10L
Overview of Spectroscopy
Spectroscopy Based on Absorption
UV/Vis and IR Spectroscopy
Atomic Absorption Spectroscopy
Emission Spectroscopy
Photoluminescent Spectroscopy
Atomic Emission Spectroscopy
Spectroscopy Based on Scattering
Key Terms
Chapter Summary
Problems
Solutions to Practice Exercises
An early example of a colorimetric analysis is Nessler’s method for ammonia, which was
introduced in 1856. Nessler found that adding an alkaline solution of HgI2 and KI to a dilute
solution of ammonia produces a yellow to reddish brown colloid, with the colloid’s color
depending on the concentration of ammonia. By visually comparing the color of a sample to the
colors of a series of standards, Nessler was able to determine the concentration of ammonia.
Colorimetry, in which a sample absorbs visible light, is one example of a spectroscopic
method of analysis. At the end of the nineteenth century, spectroscopy was limited to the
absorption, emission, and scattering of visible, ultraviolet, and infrared electromagnetic radiation.
Since its introduction, spectroscopy has expanded to include other forms of electromagnetic
radiation—such as X-rays, microwaves, and radio waves—and other energetic particles—such
as electrons and ions.
543
544
Analytical Chemistry 2.0
10A
Overview of Spectroscopy
he focus of this chapter is on the interaction of ultraviolet, visible, and
infrared radiation with matter. Because these techniques use optical materials to disperse and focus the radiation, they often are identiied as optical
spectroscopies. For convenience we will use the simpler term spectroscopy
in place of optical spectroscopy; however, you should understand that we
are considering only a limited part of a much broader area of analytical
techniques.
Despite the diference in instrumentation, all spectroscopic techniques
share several common features. Before we consider individual examples in
greater detail, let’s take a moment to consider some of these similarities.
As you work through the chapter, this overview will help you focus on
similarities between diferent spectroscopic methods of analysis. You will
ind it easier to understand a new analytical method when you can see its
relationship to other similar methods.
10A.1 What is Electromagnetic Radiation
Figure 10.1 he Golden Gate bridge as
seen through rain drops. Refraction of light
by the rain drops produces the distorted
images. Source: Mila Zinkova (commons.
wikipedia.org).
Electromagnetic radiation—light—is a form of energy whose behavior
is described by the properties of both waves and particles. Some properties
of electromagnetic radiation, such as its refraction when it passes from one
medium to another (Figure 10.1), are explained best by describing light as
a wave. Other properties, such as absorption and emission, are better described by treating light as a particle. he exact nature of electromagnetic
radiation remains unclear, as it has since the development of quantum
mechanics in the irst quarter of the 20th century.1 Nevertheless, the dual
models of wave and particle behavior provide a useful description for electromagnetic radiation.
WAVE PROPERTIES OF ELECTROMAGNETIC RADIATION
Electromagnetic radiation consists of oscillating electric and magnetic ields
that propagate through space along a linear path and with a constant velocity. In a vacuum electromagnetic radiation travels at the speed of light,
c, which is 2.997 92 � 108 m/s. When electromagnetic radiation moves
through a medium other than a vacuum its velocity, v, is less than the speed
of light in a vacuum. he diference between v and c is suiciently small
(
Spectroscopic Methods
Chapter Overview
Section 10A
Section 10B
Section 10C
Section 10D
Section 10E
Section 10F
Section 10G
Section 10H
Section 10I
Section 10J
Section 10K
Section 10L
Overview of Spectroscopy
Spectroscopy Based on Absorption
UV/Vis and IR Spectroscopy
Atomic Absorption Spectroscopy
Emission Spectroscopy
Photoluminescent Spectroscopy
Atomic Emission Spectroscopy
Spectroscopy Based on Scattering
Key Terms
Chapter Summary
Problems
Solutions to Practice Exercises
An early example of a colorimetric analysis is Nessler’s method for ammonia, which was
introduced in 1856. Nessler found that adding an alkaline solution of HgI2 and KI to a dilute
solution of ammonia produces a yellow to reddish brown colloid, with the colloid’s color
depending on the concentration of ammonia. By visually comparing the color of a sample to the
colors of a series of standards, Nessler was able to determine the concentration of ammonia.
Colorimetry, in which a sample absorbs visible light, is one example of a spectroscopic
method of analysis. At the end of the nineteenth century, spectroscopy was limited to the
absorption, emission, and scattering of visible, ultraviolet, and infrared electromagnetic radiation.
Since its introduction, spectroscopy has expanded to include other forms of electromagnetic
radiation—such as X-rays, microwaves, and radio waves—and other energetic particles—such
as electrons and ions.
543
544
Analytical Chemistry 2.0
10A
Overview of Spectroscopy
he focus of this chapter is on the interaction of ultraviolet, visible, and
infrared radiation with matter. Because these techniques use optical materials to disperse and focus the radiation, they often are identiied as optical
spectroscopies. For convenience we will use the simpler term spectroscopy
in place of optical spectroscopy; however, you should understand that we
are considering only a limited part of a much broader area of analytical
techniques.
Despite the diference in instrumentation, all spectroscopic techniques
share several common features. Before we consider individual examples in
greater detail, let’s take a moment to consider some of these similarities.
As you work through the chapter, this overview will help you focus on
similarities between diferent spectroscopic methods of analysis. You will
ind it easier to understand a new analytical method when you can see its
relationship to other similar methods.
10A.1 What is Electromagnetic Radiation
Figure 10.1 he Golden Gate bridge as
seen through rain drops. Refraction of light
by the rain drops produces the distorted
images. Source: Mila Zinkova (commons.
wikipedia.org).
Electromagnetic radiation—light—is a form of energy whose behavior
is described by the properties of both waves and particles. Some properties
of electromagnetic radiation, such as its refraction when it passes from one
medium to another (Figure 10.1), are explained best by describing light as
a wave. Other properties, such as absorption and emission, are better described by treating light as a particle. he exact nature of electromagnetic
radiation remains unclear, as it has since the development of quantum
mechanics in the irst quarter of the 20th century.1 Nevertheless, the dual
models of wave and particle behavior provide a useful description for electromagnetic radiation.
WAVE PROPERTIES OF ELECTROMAGNETIC RADIATION
Electromagnetic radiation consists of oscillating electric and magnetic ields
that propagate through space along a linear path and with a constant velocity. In a vacuum electromagnetic radiation travels at the speed of light,
c, which is 2.997 92 � 108 m/s. When electromagnetic radiation moves
through a medium other than a vacuum its velocity, v, is less than the speed
of light in a vacuum. he diference between v and c is suiciently small
(