Cold Hg Vapor Technique

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Cold Hg Vapor Technique

• Hg2 Sn2 ? Hgo Sn4
• The elemental Hg is swept from the flask into a
  long path absorption cell in the path of a Hg
  HCL.
• With a 50 mL sample,
  LOD is 20 ng/L (20 pg/mL)

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Hydride Generation

• NaBH4 is added to form hydride
• Works with As, Se, Te, Sb, Bi, Sn, Ge.
• The hydride is decomposed to atoms in a flame, or
  a heated quartz cell.
• LOD about 0.1 1 ppb similar to furnace

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Advantages

• Some of the hydride-forming elements have
  resonance lines at very short wavelength
  (eg As and Se, below 200 nm)
• At these wavelengths, conventional flames absorb
  much radiation.
• Therefore flame fluctuates ?Noisy signals
• The diffusion (low temperature) flames used to
  decompose hydrides are transparent at the low
  wavelengths. The heated quartz cell is even
  better.

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Additional Advantages

• Interferences are often reduced
• They are left behind when the hydride is swept
  away
• Therefore you can analyze more complex samples
• viscous
• High salt content
• High suspended solids

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