Atomic absorption spectrometry

Cards (7)

    • 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