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Atomic Emission Spectroscopy

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Excitation for wide range of elements under same conditions ... Cross flow of Ar. Fine droplets carried by gas into plasma. Ultrasonic method can also be used ... – PowerPoint PPT presentation

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Title: Atomic Emission Spectroscopy


1
Atomic Emission Spectroscopy
  • Emission sources
  • Applications
  • Samples
  • AES operates by exciting elements
  • Rapid relaxation accompanied by emission of UV or
    visible light
  • Properties
  • Low interelement interference
  • Excitation for wide range of elements under same
    conditions
  • High temperatures

2
Sources
  • Plasma source
  • Ar plasma generally used
  • High temperatures
  • Inductively coupled plasma (ICP)
  • Direct current plasma (DCP)
  • Microwave induced plasma (MIP)
  • ICP and DCP are main sources

3
ICP source
  • ICP torch components
  • Ar gas
  • 5-20 L/min
  • 3 quartz tubes
  • RF source
  • 0.5-2 kW
  • 27 or 41 MHz
  • Ionization initiated by Tesla coil
  • Ions and e- interact with magnetic field
  • Flow and heating
  • Quartz cooling by Ar

4
Sample introduction
  • Samples in Ar in torch center
  • Nebulizers used for liquid samples
  • Cross flow of Ar
  • Fine droplets carried by gas into plasma
  • Ultrasonic method can also be used
  • Electrothermal vaporization
  • Ablation

5
Electrothermal vaporization
6
Plasma Characteristics
  • Large temperature variation
  • Spectra collected 15-20 mm above coil
  • Free from Ar
  • Ar is chemically inert
  • No oxide formation
  • Little reabsorption

7
Direct Current Plasma
  • 3 electrodes
  • 2 graphite anode
  • Ar flows from anode to cathode
  • Contact between anode and cathode
  • 10 000 K to 5 000 K

8
Spectrometers
  • Most spectrometer from 170 nm to 800 nm
  • 3 basic types
  • Sequential
  • Simultaneous multichannel
  • Fourier transform
  • Sequential
  • Move from one element line to the next
  • Different components for UV and visible

9
Spectrometers
  • Multichannel
  • Simultaneous collection of different wavelengths
  • Requires more detectors
  • CCD or PMT

10
ICP-AES
11
Samples
  • Dissolved samples
  • Introduction and retention of samples can cause
    errors
  • Wide variety of elements
  • Most elements have several emission lines
  • Calibration normally linear
  • Self-absorption can limit linearity

12
Elements detected by AES
13
ICP-AES data
14
Calibration curve
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