341
radiation when they are energized to excite their external electrons. Since electrons
can only exist at certain energy levels, specific to each element, the wavelength of
the emitted radiation itself is characteristic of a given element. This characteristic
emission gives the opportunity not only for qualitative but also for quantitative analysis, because the intensity of the emitted radiation is directly proportional to the
number of atoms or ions that is emitted. The emission of light from each element,
with a certain wavelength, allows this physical phenomenon to be used as a very
sensitive and specific method of analysis. It is characteristic that the external electrons of the atoms of many metals are more easily excited than those of nonmetals
(Linge 2009).
The basic principles on which emission spectroscopy is based are the acquisition
of line spectra emitted by excited atoms or ions in the vapor state after the absorption of adequate energy. Electronic levels are quantized and under normal conditions are in the lowest energy state, known as the normal or ground state. Sufficient
energy is delivered to the atom or ion, thermally or by means of an electric source;
one or more electrons can be converted to a higher energy state. The excited atom is
held for a very short time, and when the electrons return from the higher energy
state to the ground state, radiation is emitted.
When the atom returns to its ground state, the electron can make several specific
jumps or energy changes, emitting radiation of different wavelengths. When using
high-energy excitation sources, a larger number of lines usually appear, the intensity
of which depends on the number of atoms emitting energy and the amount of energy.
The number of lines is determined by the number of transitions from different levels
and the intensity by the number of electrons emitting energy.
In emission methods, arc, spark, flame, or plasma can be used as excitation or
excitation agents for atoms. Emission tests obtained from arc, spark, or argon
plasma indicate the existence of three types of spectra: continuous, band, and linear.
At arc and spark sources, continuous radiation is emitted from the heated particles
obtained from the surface of the electrodes. Band spectra, obtained from a series of
close lines, are observed in some wavelength ranges, especially in arc and spark
sources. Emission spectrometry is based on linear spectra obtained by excitation of
atoms and ions. Atomic line spectra are important from the point of view of analytical purposes, because there are no identical line spectra for two elements.
If molecules or atoms in the gaseous state are provided with sufficient energy, the
chemical bonds are broken. The result of this process is the creation of an ionized
gas called plasma. Plasma is composed of a large number of free electrons and a
number of free positively charged ions, i.e., plasma is electrically neutral and is the
fourth aggregate state of matter. Plasma means partially and completely ionized
gases. The ions created in the plasma are able to absorb enough energy from an
external source to maintain the temperature at a level at which further ionization
keeps the plasma stable and a temperature higher than 10,000 K. This state of matter
contains a large amount of energy per unit volume and is therefore a suitable
excitation source in emission spectrometry. Microscopically, plasma behaves like
any other gas, and macroscopically it behaves like a liquid: it conducts electricity
and transmits different types of waves. Laboratory plasma is produced from a gas
11 Chemical Composition and Nutritional Properties of Functional Food
radiation when they are energized to excite their external electrons. Since electrons
can only exist at certain energy levels, specific to each element, the wavelength of
the emitted radiation itself is characteristic of a given element. This characteristic
emission gives the opportunity not only for qualitative but also for quantitative analysis, because the intensity of the emitted radiation is directly proportional to the
number of atoms or ions that is emitted. The emission of light from each element,
with a certain wavelength, allows this physical phenomenon to be used as a very
sensitive and specific method of analysis. It is characteristic that the external electrons of the atoms of many metals are more easily excited than those of nonmetals
(Linge 2009).
The basic principles on which emission spectroscopy is based are the acquisition
of line spectra emitted by excited atoms or ions in the vapor state after the absorption of adequate energy. Electronic levels are quantized and under normal conditions are in the lowest energy state, known as the normal or ground state. Sufficient
energy is delivered to the atom or ion, thermally or by means of an electric source;
one or more electrons can be converted to a higher energy state. The excited atom is
held for a very short time, and when the electrons return from the higher energy
state to the ground state, radiation is emitted.
When the atom returns to its ground state, the electron can make several specific
jumps or energy changes, emitting radiation of different wavelengths. When using
high-energy excitation sources, a larger number of lines usually appear, the intensity
of which depends on the number of atoms emitting energy and the amount of energy.
The number of lines is determined by the number of transitions from different levels
and the intensity by the number of electrons emitting energy.
In emission methods, arc, spark, flame, or plasma can be used as excitation or
excitation agents for atoms. Emission tests obtained from arc, spark, or argon
plasma indicate the existence of three types of spectra: continuous, band, and linear.
At arc and spark sources, continuous radiation is emitted from the heated particles
obtained from the surface of the electrodes. Band spectra, obtained from a series of
close lines, are observed in some wavelength ranges, especially in arc and spark
sources. Emission spectrometry is based on linear spectra obtained by excitation of
atoms and ions. Atomic line spectra are important from the point of view of analytical purposes, because there are no identical line spectra for two elements.
If molecules or atoms in the gaseous state are provided with sufficient energy, the
chemical bonds are broken. The result of this process is the creation of an ionized
gas called plasma. Plasma is composed of a large number of free electrons and a
number of free positively charged ions, i.e., plasma is electrically neutral and is the
fourth aggregate state of matter. Plasma means partially and completely ionized
gases. The ions created in the plasma are able to absorb enough energy from an
external source to maintain the temperature at a level at which further ionization
keeps the plasma stable and a temperature higher than 10,000 K. This state of matter
contains a large amount of energy per unit volume and is therefore a suitable
excitation source in emission spectrometry. Microscopically, plasma behaves like
any other gas, and macroscopically it behaves like a liquid: it conducts electricity
and transmits different types of waves. Laboratory plasma is produced from a gas
11 Chemical Composition and Nutritional Properties of Functional Food