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Cold Hg Vapor Technique

This technique involves the use of hydride generation to analyze samples containing elements such as As, Se, Te, Sb, Bi, Sn, and Ge. The hydride is decomposed into atoms in a flame or heated quartz cell, providing a LOD of approximately 0.1-1 ppb. The method offers advantages such as reduced interferences and the ability to analyze complex samples with high salt content or suspended solids.

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Cold Hg Vapor Technique

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  1. 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)

  2. 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

  3. 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.

  4. 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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