Atomic Absorption
Spectrophotometer
Contents
oPrinciple
oInstrumentation
oSOPs for Atomic Absorption Spectroscopy
oTrouble Shooting of AAS
oSoil Plant Extraction for Heavy Metal analysis
oApplications of AAS
Principle
Atomic absorption spectroscopy (AAS) is based upon the
principle that free atoms in the ground state can absorb light of a
certain wavelength. Absorption for each element is specific, no
other elements absorb this wavelength.
Instrumentation
Nebulizer
Atomizer
Atomic Absorption
Spectrophotometer
Hollow Cathode
Detector
Lamp
Mono
chromator
Nebulizer
A nebulizer is a device that
introduces a liquid sample into
the AAS. Here, we will discuss
the most common types:
pneumatic and
ultrasonic nebulizers. A
pneumatic nebulizer converts
a sample solution into an
aerosol of tiny droplets using a
jet of compressed gas.
Atomizer
Atomic-Absorption
Spectroscopy requires the
conversion of the sample to
gaseous atoms, which absorb
radiation. When the mist
reaches the flame, the intense
heat breaks up the sample into
its individual atoms.
Hollow cathode lamps
Hollow cathode lamps (HCL)
are discharge lamps designed
for use in Atomic
Absorption (AA) instruments.
They consist of a cathode made
from the element of interest, an
anode and an inert filler gas
contained in a glass envelope.
Monochromator
The monochromator is
included as an important
device of the optical system of
an atomic absorption
spectrophotometer. The
function of this device
in atomic absorption is to
separate the spectral line of
interest from others spectral
lines with different
wavelengths emitted by the
hollow-cathode lamp.
Detector
In Atomic Absorption
Spectroscopy, the amount of
radiation that passes through a
sample is measured and
quantitatively described by
transmittance.
SOPs for Atomic Absorption Spectroscopy
Brand: Analytic Jena Model: novAA
400
For flame:
• Acetylene (is essential and used as
fuel) at pressure (1.4-1.5 bars)
• Nitrous oxide or compressed air (4-
6 bars)
• Do not use when gas is less than 120
bars
SOPs for Atomic Absorption Spectroscopy
Exhaust:
Software
Must turn on the exhaust
before start working (aspect LS)
SOPs for Atomic Absorption Spectroscopy
Precautionary Measures: How to turn it on?
• Turn off the lights • Turn on the power button of
• Turn of the fan exhaust fan, computer system and
atomic absorption spectrum (on
• Fresh distilled water should be lower right side of AAS)
placed for the AAS nebulizer
• Turn on the gas
• Check the EC of distilled water
being used • Gas pressure
should be 1.5 bars
Facility of Elements in MNSUAM
Soil, plant water analytical Lab
Ca
Nickle
NI MG Fe ZN
Calcium Magnesium Iron Zinc
Soil Extraction for Analysis of Heavy
Metals
Di-Acid (HNO3-HClO4), Block Digester
Apparatus
• Digestion tube
• Block-digester
• Atomic Absorption Spectrophotometer
Reagent
• Nitric Acid (HNO3), concentrated
• Perchloric Acid (HClO4), concentrated
Soil Extraction for Analysis of Heavy
Metals
Procedure
1. Weigh 0.5-1.0 g air-dry soil (0.15-mm) into a 300-mL calibrated digestion tube.
2. Add 3 mL concentrated HNO3 (in the fume hood), and swirl carefully, and then
place tubes in the rack.
3. Place the tubes rack in the block-digester, and then place a glass funnel in the
neck of the tubes. Slowly increase temperature setting to about 145 °C for 1 hour.
4. Add 4 mL concentrated HClO4 and heat it to 240 oC for further 1 hour.
5. Lift the tubes rack out of the block-digester, carefully place on a rack holder, and
let tubes cool to room temperature.
6. Filter through Whatman No. 42 filter paper and bring to 50-mL volume.
7. Each batch should contain at least one reagent blank (no soil).
8. Determine Fe, Mn, Cu, Zn, Cd, Ni, Pb, Co, and Cr by Atomic Absorption
Spectrophotometer.
Plant Extraction for Analysis of Heavy
Metals
Di-Acid (HNO3-HClO4) , Block Digester
• Digestion tube
• Block-digester
• Atomic Absorption Spectrophotometer
Reagent
Di-acid digestion (HNO3-HClO4)
Mix grade concentration HNO3 and HClO4 in 9:4 ratios, and let
it cool.
Plant Extraction for Analysis of Heavy
Metals
Procedure
1. Weigh 0.5-1.0 g dry and ground plant material into a 300-mL calibrated digestion tube (or into a
150-ml conical flask).
2. Add 5 mL concentrated HNO3 (in the fume hood), and swirl carefully and then place tubes in the
rack. .
3. Place a glass funnel on the calibrated digestion tube and leave for about 6-8 hours.
4. After pre-digestion, add 10 mL di-acid mixture, swirl carefully.
5. Place the tubes rack in the block-digester, and then place a glass funnel in the neck of the tubes.
Slowly increase temperature setting to about 180-200 °C until the dense white fumes evolve and
transparent white contents are left.
6. Lift the tubes rack out of the block-digester, carefully place on a rack holder, and let tubes cool to
room temperature.
7. Filter through Whatman No. 1 filter paper, and bring to 50-mL volume.
8. Determine Fe, Mn, Cu, Zn, Cd, Ni, Pb, Co, and Cr by Atomic Absorption Spectrophotometer.
9. Each batch of samples for digestion should contain at least one reagent blank (no plant).
Calculation
Soil
Plant
Application of AAS
Atomic absorption spectroscopy is utilized across many
industries and is instrumental in the detection of metals within a
sample. As such, this process is commonly utilized in;
• pharmacology
• manufacturing
• mining
• Forensics
• Environmental studies; Drinking water, ocean, soil
