Transcript Atomic Absorption Spectroscopy

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ATOMIC ABSORPTION SPECTROSCOPY
By
Hisham E Abdellatef
Advanced Flame and Graphite Furnace Atomic Absorption Spectroscopy
Course Instructor: prof. Dr. Hisham Ezzat Abdellatef
Flame
Principles of Operation Review
Optimizing the Flame
Multielement vs Single Element Lamps
Lamp Performance Check
Increasing the Linear Range
Slit Selection
Background Correction
Air Acetylene and Nitrous Oxide Flames
Matrix Modifiers
Instrument Detection Limits (IDL),
Method Detection Limits (MDL), and
Limits of Quantification (LOQ)
Basic Quality Control
Hydride Generation
Mercury Cold Vapor
Furnace
Principles of Operation
Background Correction and Performance
Checks
The Three Steps Dry, Char, Atomize
How to Enhance each Step and Modifiers
Handling Difficult Matrixes
Graphite Tube Selection
Quality Controls
Detection Limits
Quality Assurance
Method development/Standard Operating
Procedures (SOP)
EPA Quality Assurance programs
Standards/Blanks
Introduction
• AAS is used to determine metal element
concentration in a sample
• Can analyze over 62 metal elements
• Cold Vapor AA, Flame AA, and Graphite furnace AA
• Standard addition and standard calibration
technique can be used to compute for metal
element concentration
Technique – Flame Test
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Atomic Absorption Spectroscopy:
An Aussie Invention
• Developed by Alan Walsh in early 1950s.
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Introduction
ATOMS
Bohr’s shell model:
SODIUM atom
Electrons
Nucleus
Shells
• Nucleus- protons
(+ve) and neutrons
(neutral).
• Electrons- (-ve)
charged particle.
• Shells- consists of
subshells.
Shell, Subshells, Electrons
• Electrons are arranged according to their
energy levels. They are arrange in subshells,
the subshells are arrange in shells and shells
are arrange around the nucleus.
Atom
(around the nucleus)
!Note:
Electrons that are near the nucleus has
a lower energy level than the electrons
that are much far away. However, they
experience stronger attraction in the
nucleus than those ones that are
further away.
Shells
Subshells
Electrons
‘Exciting’ atoms
• ‘ground’ state: is a status where the atom’s
electrons are in their lowest possible energy
level. (stable)
• ‘excited’ state: another status where the
atom’s electrons absorb enough energy to
be promoted to a higher level. Therefore,
they are not in their lowest energy level.
(unstable)
‘Excited’ atom
Generally, atoms are
in their ‘ground state’
but when an atom
receives enough input
of energy that their
electrons requires to
be promoted to a
higher energy level.
They will then turn to
their ‘excited state’.
Ground
state:
Excited state:
sodium atom
Since, an atom’s excited
state is very unstable it
rapidly ‘jump’ back down
to its ground state. This
‘jump’ then causes the
atom to release the
energy it absorbed in the
form of photons of light.
!Note:
Take note that the
electron can go back
down to its ‘original’
place in more than
one jump.