Atomic spectrometry 403426, Slides of Geology

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ATOMIC SPECTROMETRY

• AAS (absorption in the visible or UV regions) Flame (FAAS) electro thermal graphite cell (ETAAS)
• AFS
• AES (emission of energy by excited atoms as visible (OES) or UV waves)

ATOMIC ABSORPTION SPECTROMETRY

• Cheap and fast
  • Good for high volume routine analysis
• In principle it uses the same physics as OES but in reverse
• Graphite furnaces can have memory effects similar to spark sources

TYPES OF AAS (DEFINED BY ATOMIZER)

Flame (FAAS) Air-acetylene (2300 C) N 2 O-acetylene (2700 C) Graphite furnace (GFAAS), also called electrothermal (ETAAS) 2-3x more sensitive than FAAS, but ‘memory’ effects Hollow cathode ray tube (HCRAAS) Cathode is made of element of interest

ATOMIC (OPTICAL) EMISSION SPECTROMETRY

• One of the first and still in regular use in industrial labs especially for water analysis
• Samples need to be in solution (problems with for eg. Zr, REE and Cr) which occur in very refractory minerals which are very difficult to dissolve.

The removal of solvent from a material in solution Dissolved sample is vaporised.

APPLICATION OF AS

Hg monitoring  very toxic, especially if methylated  concentration increases up the food chain  low levels (ppt range) are significant Sources  coal-fired power stations  internal combustion engines  alluvial gold mining  medical and dental waste Analytical problems  ultra-trace levels need to be detected, so a very low detection limit is required  rapid turn-around time Best practice  dissolution in MnO 4

• -SO 4 - to oxidize the Hg to (II) state  add SnCl 2 to reduce to Hg 0  use cold-vapour input into AFS instrument