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second is the σ component, which undergoes both a positive and negative shift in wavelength,

resulting in two equally spaced lines on either side of the original line. This splitting pattern is

presented in Fig. The splitting results in lines that are separated by approximately 0.01 nm or less
depending on the field strength. The strength of the magnetic field used is between 7 and 15

kgauss. Background absorption and scatter are usually not affected by a magnetic field. The π
and σ components respond differently to polarized light. The π component absorbs light

polarized in the direction parallel to the magnetic field. The σ components absorb only radiation

polarized 90º to the applied field. The combination of splitting and polarization differences can
be used to measured total absorbance (atomic plus background) and background only, permitting

the net atomic absorption to be determined.
A permanent magnet can be placed around the furnace to split the energy levels. A

rotating polarizer is used in front of the HCL or EDL. During that portion of the cycle when the
light is polarized parallel to the magnetic field, both atomic and background absorptions occur.

No atomic absorption occurs when the light is polarized perpendicular to the field, but

background absorption still occurs. The difference between the two is the net atomic absorption.
Such a system is a DC Zeeman correction system.

ANALYTICAL APPLICATIONS OF AAS

AAS is a mature analytical technique. There are thousands of published methods for

determining practically any element in almost any type of sample. There are books and journals
devoted to analytical methods by AAS and other atomic spectrometry techniques. The

bibliography provides a list of some texts on AAS. Journals such as Analytical Chemistry,
Applied Spectroscopy, Journal of Analytical Atomic Spectroscopy, The Analyst, Spectroscopy

Letters, and others are sources of peer-reviewed articles, but many applications articles can be

found in specialized journals on environmental chemistry, food analysis, geology, and so on. The
applications discussion here is necessarily limited, but the available literature is vast.

AAS is used for the determination of all metal and metalloid elements. Nonmetals cannot
be determined directly because their most sensitive resonance lines are located in the vacuum

UV region of the spectrum. Neither flame nor furnace commercial atomizers can be operated in a
vacuum. It is possible to determine some nonmetals indirectly by taking advantage of the

insolubility of some compounds.

For example, chloride ion can be precipitated as insoluble silver chloride by adding a
known excess of silver ion in solution (as silver nitrate). The silver ion remaining in solution can

be determined by AAS and the chloride ion concentration calculated from the change in the
silver ion concentration. Similar indirect approaches for other nonmetals or even polyatomic ions

like sulfate can be devised.

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