Atomic Emission Spectrometry

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Atomic Emission Spectrometry
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Plasma
Ar
e-
Ar
e-
Plasma is an electrical conducting gaseous
mixture containing a significant concentration of
cations and electrons.
e-
e-
e-
Ar
Ar
Argon ions once formed can absorb energy from
external sources and maintain temperature to
sustain plasma indefinetly.
e-
e-
Ar

• Types of high temperature plasmas
• Inductively coupled plasma
• Direct current plasma
• Microwave induced plasma

Ar
e-
Ar
Ar
3
Inductively Coupled Plasma Torch
Radio frequency induction coil 27-41 MHz 0.5-2KW
Plasma torch F 2.5 cm
Tangential flow isolates the torch from plasma
Plasma argon
Sample argon
Argon flow rate 5-20 L/min
Tangential argon plasma support flow
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Sample Introduction
Plasma argon
Auxiliary plasma argon
Aerosol carrier Argon
Sample solution
To drain
5
Electrothermal Vaporization
To ICP
Sample
Graphite rod
Heater power
Water coolant
Argon inlet
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Temperature in a Typical ICP Source
Temperature oK (10)
6000
25
6200
20
Height above load coil mm
6500
15
6800
8000
10000
7
Radial ICP Source
To spectrometer
4 to 10 fold improvement in detection limit
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Three Electrode DC Plasma Jet
Plasma column
Excitation region
Anode block
Ceramic sleeve
Electrode
Electrode
Anode block
Sample and Argon
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Desirable Properties of Emission Spectrometers

• High resolution (0.01 nm)
• Rapid signal acquisition and recovery
• Low stray light
• Wide dynamic range
• Accurate and precise wavelength selection
• Precise intensity reading
• High stability with respect to environmental
  changes
• Easy background correction
• Computerized operation readout, storage, ...

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Plasma Source Spectrometers

• Simultanuos or multichannel
• Sequential

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Slew Scan Spectrometer
Exit slit
Composite grating
Mirror
Filter wheel
Photomultiplier tubes
Motorized observation height
Plasma torch
Mirrors
Hg lamp
Entrance slit
12
Diffraction grating
Position feedback
Capacitive transducer
17-Bit DAC
Rotor shaft
5
Servo amp
Eelectromagnetic coil
Magnetically driven grating
13
Echelle Polychromator
Aperature plate
Prism/lens
Echelle grating
Plane mirror
Computer adjustable source mirror
Collimating mirror
Entrance slit
Source
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Multichannel Spectrometers

• Polychromator
• Array-based systems

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Measuring electronics
Dedicated computer
Instrument control electronics
Schematic of an ICP polychromator
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Applications

• Sample preparation
• Elements determined
• Line selection
• Calibration curves
• Interferences
• Detection limits

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H
He
Li
Be
B
C
N
O
F
Ne
Al
Si
P
S
Cl
Ar
Na
Mg
K
Ca
Sc
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
Ga
Ge
As
Se
Br
Kr
I
Xe
Rb
Sr
Y
Zr
Nb
Mo
Tc
Ru
Rh
Pd
Ag
Cd
In
Sn
Sb
Te
Ti
Pb
Bi
Po
At
Rn

Cs
Ba
Hf
Ta
W
Re
Os
Ir
Pt
Au
Hg

Fr
Ra
La
Ce
Pr
Nd
Pm
Sm
Eu
Gd
Dy
Ho
Tm
Yb
Lu
Tb
Er
Th
Pa
U
Np
Pu
Am
Cm
Md
No
Lr
Bk
Ac
Cf
Es
Fm
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Typical Calibration Curves
Tl 334.94 nm
10
Photocurrent ( na)
1
V 437.92 nm
Nb 371.30 nm
Ce 456.24 nm
0.001
0.0001
0.1
0.01
Impurity concentration in iron ( wt)
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Calibration Curve
Ba
Deionized water
Cr
5000 mg/mL Na
Cd
Tap water (500 ppm hardness)
Zn
Pb
200 mg/mL Ca, 200 mg/mL Mg ( all solutions 0.1 M
HCl)
Intensity ratio
0.03
0.1
0.3
1.0
3.0
10
Concentration mg/mL
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Suggestions Appreciated! Chemistry
Depatement, Shiraz University,
IRAN nzmaleki_at_gmail.com Sites.google.com/site/simi
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