Atomic absorption spectrometry

• • Use specific wavelength (Energy from photons) --> Excite atoms [from ground state (most stable) to excited state]
  • Amount of energy absorbed = Concentration of atoms
  • Diff. wavelength, Diff. energy
• • Absorb/ Emit light b/c electronic composition; Distinguish energy level based on electron shell occupying
  • No. of electron in each atom is diff.; can test multiple species of atoms at the same time (diff. absorbance characteristic)
• Only be performed on GASEOUS medium (individual atoms/ ions well-separated)
• Atomization:

  • Use flames, graphite furnace (electrothermal), plasma atomizers [use heat to vaporize sample]
  • Function: Decompose + Volatilize samples --> Produce gas-phase analyte atoms/ ions
• Graphite Furnace Atomic Absorption Spectrometry

  • Quantify elements + trace + ultra trace levels using very small samples
• Graphite Furnace Atomic Absorption Spectrometry

  Procedure:

  • Place sample inside a graphite tube
  • Heated for sample desolvation (for liquid samples); ashing/ charring (decompose sample and volatilize some of the matrix)
  • Atomization (Occurs in an env. where temp is more stable so signals are more reproducible)
• Beer-Lambert Law: Defined relationship between absorbance & conc. of the absorbing sample

  • Absorbance = Molar absorption coefficient x Molar concentration x Path length