Cold Hg Vapor Technique

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)

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

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.

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