FORENSIC USE OF ATOMIC ABSORPTION SPECTROSCOPY

1. ATOMIC ABSORPTION
SPECTROSCOPY
SUMIT SWAMI
Reg no: 11804251
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2. CONTENTS
▪ Introduction
▪ Principle of AAS.
▪ Instrumentation
▪ Sample preparation
▪ Applications.
▪ Role in forensic science

3. INTRODUCTION
▪ Atomic Absorption Spectroscopy is a very
common technique for detecting metals and
metalloids in samples.
▪ It is very reliable and simple to use.
▪ It can analyze over 62 elements
▪ It also measures the concentration of metals
in the sample.
▪ Elements detectable by atomic absorption are
highlighted in pink in this periodic table

4. Principle:
• In gaseous state atoms absorb ultraviolet or
visible light and make transitions to higher
electronic energy levels.
• The wavelength of each transition is specific
to each element – qualitative analysis
• Beer-Lambert’s law can be applied to find
concentrations using a calibration graph
prepared from standards
• Absorbance is directly proportional to path
length and concentration
Instrumentations:
1. Hollow Cathode Lamp
2. Nebulizer
3. Atomizer
4. Monochromator
5. Detector

5. 1. Hollow Cathode Lamp:
• Hollow Cathode Lamp is the most
common radiation source in AAS.
• It contains a tungsten anode and a hollow
cylindrical cathode made of the element to
be determined.
• These are sealed in a glass tube filled with
an inert gas (neon or argon).
• Each element has its own unique lamp
which must be used for that analysis.
2. NEBULIZER:
• Suck up liquid samples at controlled rate.
• Create a fine aerosol spray for introduction
into flame.
• Mix the aerosol and fuel and oxidant
thoroughly for introduction into flame.

6. 3. ATOMIZER
• Elements to be analyzed needs to be in
atomic sate.
• Atomization is separation of particles into
individual molecules and breaking
molecules into atoms. This is done by
exposing the analyte to high temperatures
in a flame or graphite furnace.
There are two type of atomizer. Such as:
1. FLAME ATOMIZERS
2. GRAPHITE TUBE ATOMIZERS
Flame Atomizer Graphite tube Atomizer

7. 4. MONOCHROMATOR
• This is a very important part in an AA
spectrometer. It is used to separate out all of
the thousands of lines.
• A monochromator is used to select the
specific wavelength of light which is
absorbed by the sample, and to exclude other
wavelengths.
• The selection of the specific light allows the
determination of the selected element in the
presence of others.
5. DETECTOR
• The light selected by the monochromator is
directed onto a detector that is typically a
photomultiplier tube, whose function is to
convert the light signal into an electrical
signal proportional to the light intensity.
• The processing of electrical signal is fulfilled
by a signal amplifier. The signal could be
displayed for readout, or further fed into a
data station for printout by the requested
format.

8. Sample Preparations:
• Dilution – sample is diluted in distilled
water, acids or organic solvent
• Decomposition – isolation of required
element from the sample by heating
with/without a reagent
– Wet/acid decomposition (300C)
– Dry ashing (400-500C) - destroying the
combustible portion of the sample. Oxidizing
agents may be used
– Microwave decomposition (100-200C) –
sample decomposed at high pressures in a Teflon
container
• Calibration curve must be prepared using
different concentrations of the sample.

9. Applications:
• Determination of even small amounts of metals
(lead, mercury, calcium, magnesium, etc.) as
follows:
▪ Environmental studies: drinking water,
ocean water, soil.
▪ Food industry.
▪ Pharmaceutical industry.
• Examples:
▪ DETERMINATION OF VANDIUM
IN LUBRICATING OIL
▪ DETERMINATION OF TRACE
ELEMENTS IN CONTAMINATED
SOIL

10. Role in Forensic Science:
▪ Determination of trace elements.
▪ Elemental profiles of biological samples.
▪ Trace elements in artificial fibers.
▪ Determination of the mode of poisoning.
▪ Hair analysis for heavy metal poisons.
▪ Determination of ammunition manufacturers.
▪ Discrimination of objects/Elements.