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Atomic Emission Spectroscopy

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.

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Atomic Emission Spectroscopy

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  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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