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ENSC3520
Methods
Atomic absorption spectrometry
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Created by
Victoria Mok
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Cards (7)
Use specific
wavelength
(Energy from
photons
) -->
Excite
atoms [from
ground
state (most
stable
) to
excited
state]
Amount of energy
absorbed
=
Concentration
of atoms
Diff.
wavelength
, Diff.
energy
Absorb
/
Emit
light b/c
electronic
composition; Distinguish
energy
level based on
electron
shell
occupying
No. of
electron
in each atom is diff.; can test
multiple
species of atoms at the same time (diff.
absorbance
characteristic)
Only be performed on
GASEOUS
medium (individual atoms/ ions
well-separated
)
Atomization:
Use
flames
,
graphite furnace
(
electrothermal
),
plasma
atomizers [use
heat
to
vaporize
sample]
Function:
Decompose
+
Volatilize
samples --> Produce
gas-phase
analyte atoms/ ions
Graphite Furnace Atomic Absorption Spectrometry
Quantify
elements +
trace
+
ultra
trace
levels using very
small
samples
Graphite Furnace Atomic Absorption Spectrometry
Procedure:
Place sample inside a
graphite
tube
Heated
for sample
desolvation
(for liquid samples);
ashing
/
charring
(
decompose
sample and
volatilize
some of the matrix)
Atomization
(Occurs in an env. where temp is more
stable
so signals are more
reproducible
)
Beer-Lambert Law: Defined relationship between
absorbance
&
conc.
of the absorbing sample
Absorbance =
Molar absorption coefficient
x
Molar concentration
x
Path length