SRM COLLEGE OF PHARMACY
Atomic absorption spectroscopy (AAS) is a spectro
analytical procedure for the quantitative
determination of chemical elements using the
absorption of optical radiation.
In analytical chemistry the technique is used for
determining the concentration of a particular
element in a sample to be analyzed.
AAS can be used to determine over 70 different
elements in solution or directly in solid samples
used in that.
Atomic absorption spectrometry has many
uses in different areas of chemistry such as
clinical analysis of metals in biological fluids
and tissues such as whole blood, plasma,
urine, saliva, brain tissue, liver, muscle
tissue, semen, in some pharmaceutical
manufacturing processes, minute quantities
of a catalyst that remain in the final drug
product, and analyzing water for its metal
The intensity of the light absorbed by the neutral
atoms is directly proportional to the concentration of
the element and obey the Beer’s law over wide
concentration range. The intensity of the radiation
absorbed by the neutral atoms is measured using
LIGHTSOURCE The source of the light in AAS is Hallow Cathode
Lamp(HCL). The cathode lamp is made up of specific /
alloys of elements or coating of elements on cathode. When
the current is applied between anode and cathode, metal
atoms emerge from hollow cup and collides with filler gas,
which is argon or neon. Due to these collisions, number of
metal atoms are excited and emit their characteristic
radiation. This characteristic radiation is absorbed by the
neutral atoms of the same element in ground state which
occur in the flame, when the sample sprayed.
It is not possible to use a source of light with a
Monochromator because this arrangement gives a radiation
with a band with of 1nm, where as the hollow cathode lamp
gives a band width of 0.001 to 0.01nm which is highly
desirable to achieve specificity
The temperature of the flame is not critical but atomization
of sample solution, like in flame photometry is required.
Burners with fuel and oxidant as specified in flame
photometry are used. In this air acetylene, nitrogen are use
for specific metal elements.
Air-acetylene is the preferred flame for the determination
of approximately 35 elements by atomic absorption. The
temperature of the air-acetylene flame is about 2300 °C. An
air-acetylene flame can be used Perkin-Elmer burner heads.
Length of the burner is 10cm.
Air-acetylene is the preferred flame for the determination of
approximately 35 elements by atomic absorption. The
temperature of the air-acetylene flame is about 2300 °C. An
air-acetylene flame can be used with all Perkin-Elmer
burner heads. The step-by-step procedure is given for the
operation of the acetylene/air flame. air-acetylene flame, the
acetylene flow is about 4 liters/minute
The nitrous oxide-acetylene flame has a maximum
temperature of about 2900 °C and is used for the
determination of elements which form refractory oxides. It
is also used to overcome chemical interferences that may be
present in flames of lower temperature. For the nitrous
oxide-acetylene flame, the acetylene flow is about 14 liters
per minute or 30 cubic feet per hour.
The graphite tube is just visible between the two electrodes
in the centre of the image. The electrodes are usually water-
cooled, while an inert gas is used to exclude air from the
furnace tube in order to prevent sample oxidation. The close-
up shows the view through one end of the electrode/furnace
assembly. Note the power lines and cooling water
connections on the back
GRAPHITEFURNANCE Graphite Furnace(GF) is also known as Electro thermal is
used in the type of spectrometry that uses a graphite-coated
furnace to vaporize the sample. Length of the GF is 5cm
It is applied namely for determination of trace
amounts of As, Se (Te, Sb, Ge, Sn, Pb...) . The
gaseous hydride of the analyte (e.g. AsH3 or H2Se) is
formed from the corresponding compound of the
analyte (H3AsO3 or H2SeO3) by reducing reaction
with NaBH4 (“sodium borohydride”); the reaction
takes place in a hydride generator, gaseous products
are delivered to the atomizer (usually a heated quartz
The technique is by 2-3 orders of magnitude more
sensitive than Flame AAS. As a consequence of
analyte transfer into gaseous phase most of
interferences are eliminated (namely those
manifested on analytical lines of As and Se that are
located in the region of wavelength <200 nm).
Which is used to measured to use the intensity of the
light absorbed by elements without interference by the
radiation from the flame it self. Its not practical to have
two separate cells, so the light is simply split, simply
split, with half being sent around the atomization with
half being sent around the atomization source. source.
This reduces some noise from This reduces some noise
from the atomization the atomization source and
accounts for instrumental variations. accounts for
For Good Resolution Of 1nm or Less Than 1nm Required
The intensity of radiation absorbed by the elements in the
UV / visible region (190-900nm) can be detector using
Photo Multiple Tube(PMT).
The readout device is capable of displaying the absorbing spectrum
as well the absorbance at the specified wavelength. Beer’s law is
over a wide concentration range.
Example : galvanometer(ANALOG), computer(DIGITAL).
APPLICATION OF AAS
AAS is mainly use for quantitative analysis of various
elements presents in different samples(identification).
1) Estimation of trace elements in biological fluids(Blood,
Urine, Plasma, etc.)
2) Estimation of metals like Cu, Ni, Zn in food samples.
3) Estimation of Mg, Zn, etc in blood.
4) Estimation of Zn in insulin injection.
5) Estimation of Thiomersal compounds(OrganoMercury
6) Estimation of elements in soil, water, ceramic, effluents,
DIFFERENT BETWEEN AAS and FP
by exited atoms
thermal energy of
energy of flame is
just enough to get
Near linear over
a narrow range
Its obey the
Beer’s law. Its
linear over wide
The number of
can be analyzed
by the technique
IA & IIA
Wide range of