cold hg vapor technique
DESCRIPTION
Cold Hg Vapor Technique. Hg 2+ + Sn 2+ → Hg o + Sn 4+ 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. NaBH 4 is added to form hydride - PowerPoint PPT PresentationTRANSCRIPT
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