Flame Photometry

  • A device to measure the concentration of alkali metals like Na and K by measuring the intensities of light emitted by them at high temperature.
  • Principle:-
    • As a solution in air is finally sprayed over a burner, it dissociates to give neutral atoms.
    • Some of these atoms get excited and move to a higher energy state.
    • When the excited atoms fall back to the ground state, they emit light of a characteristic wavelength which can be measured.
    • The intensity of emission light is proportional to the concentration of the electrolyte being estimated.
  • Components:-
    • Aspirator/Nebulizer/Atomizer – To produce a fine spray of droplets of uniform size necessary for constant emission of light.
    • Burner and flame- To provide heat energy to vaporize the substance and excite the electrons into higher state.
    • Monochromator/Filter- Emitted light passes through the monochromator. Eg. Orange filter for sodium(580nm) and Red filter for Potassium(766nm)
    • Phototube/Detector:- Phototube which converts light energy into electricity
    • Readout/Galvanometer- To measure the generated electricity.
  • Applications:-
    • Determining the concentration of sodium and potassium in serum, urine, sweat, etc.
    • Therapeutic use of lithium salts in the treatment of psychiatric disorders.