Product Intelligence
Atomic Absorption Spectrometry: The Science of Atomization
by Lina Genovesi
tomic absorption spectrometers (AAS) measure the concentration of atoms in a sample in the parts-per-billion range based on their ability to absorb light at a spe- cific wavelength. Most samples analyzed by AAS are liquid samples, and solid samples can also be analyzed after liquefaction.
A
There are several atomic absorption spectrom- eters to choose from depending on the specific application.
AAS methods Atomic absorption spectrometers require a light
source, an atomizer, a monochromator, and a detector. AAS systems are either flame atomic absorption spectrometers (F-AAS) or graphite atomic absorption spectrometers (G-FAAS). In F-AAS, the atomizer is a flame furnace, and in G-FAAS, the atomizer is a graphite furnace.
The sample is introduced into the atomizer. In F-AAS, the heat of the flame produces the free atoms. In G-FAAS, the electrical energy in the graphite furnace produces the free atoms.
Generally, the source for atomic absorption is a hollow cathode lamp, which provides emission lines that correspond to the analyte’s absorp- tion spectrum.
A light beam from the light source passes through the atomizer and into the monochro- mator. The free atoms absorb the light at a characteristic wavelength. The light directed into the detector produces an electrical signal proportional to the light intensity, and the in- tensity of the light absorbed is an indication of the concentration of the atoms.
Hydride vaporization method Certain elements form volatile hydrides, and
an inert gas carries the volatile hydrides to the atomizer. This method is an add-on to the flame and graphite atomization methods.
Mercury vaporization method Mercury is reduced to elemental mercury, and
an inert gas carries the elemental mercury to the atomizer. This method is used singly with specialized AAS for the determination of mer- cury or as an add-on to the flame and graphite atomization methods.
Correction for
background absorption Several methods are available for correcting
the background absorption. Subtracting the background absorption from the total absorption gives a measure of the ana- lyte absorption.
In the deuterium (D2 ) method, the light of a hol-
low cathode lamp provides a measure of the total absorption, and the light of a deuterium lamp provides a measure of the background absorption. In the high-speed self-reversal
(SR) method, the self-reversal of the power of the hollow cathode lamp provides a measure of the background absorption. In the Zeeman method, the applied magnetic field gives a measure of the background absorption.
AAS purchasing considerations In choosing an AAS, many factors should
be considered.
Application An important consideration in selecting an AAS
is its area of application.
GBC Scientific Equipment offers the SensAA and the XplorAA AAS, which are compact systems suitable for use in various areas, such as pharmaceutical, clinical, and raw mate- rial analyses.
Agilent Technologies offers the 55BAA for corrosive environments.
Table 1 – Providers of atomic absorption spectrometers Agilent Technologies Analytik Jena
Angstrom Advanced Inc. Aurora Biomed Inc. Buck Scientific
GBC Scientific Equipment Labnics Equipment PerkinElmer Inc.
PG Instruments Ltd.
Qualitest International Inc. SAFAS S.A.
Shimadzu Spectrolab Systems Thermo Fisher Scientific Inc.
Santa Clara, CA Jena, Germany Braintree, MA Vancouver, BC East Norwalk, CT Hampshire, IL Fremont, CA Waltham, MA
Richmond Hill, Ontario
Monaco
Columbia, MD Mumbai, India Waltham, MA
U-Therm International (H.K.) Ltd. Hong Kong AMERICAN LABORATORY • 34 • SEPTEMBER 2014
www.agilent.com www.analytik-jena.com
www.angstrom-advanced.com www.aurorabiomed.com www.bucksci.com
www.gbcscientific.com www.labnics.com
www.perkinelmer.com
Leicestershire, U.K.
www.pginstruments.com www.qualitest-inc.com www.safas.com
www.shimadzu.com
www.spectrolabsystems.net www.thermoscientific.com www.lab-kits.com
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