Atomic Absorption Spectroscopy Notes

Sidectin and Moxideptin

  • Sidectin, a cattle-borne iron product, contains moxideptin.
  • Moxideptin is a naturally occurring chemical produced by soil bacteria.

Emission and Absorption Machines

  • Five machines measure metals; two also measure elements like boron and chlorine.
  • Emission machines and absorption machines perform similar functions to equipment used in the previous week.
  • These machines determine concentration by measuring light absorption.
  • Samples are burned in these machines, which have burners with long, thin slots to allow light to pass through.

Machine Lamps and Light Wavelengths

  • The machine lamps differ from standard lamps.
  • Each element has specific lamps (e.g., iron, manganese).
  • Multi-element lamps emit billions of wavelengths simultaneously.
  • In the 1960s, Alan Walsh from CSIRO Melbourne developed lamps made of the same metal being analyzed.
  • These lamps emit a limited number of wavelengths, making it easier to measure light absorption for specific metals.

Atomic Absorption Process

  • The machine draws liquid samples through a capillary.
  • Samples undergo centrifuging and filtering.
  • A nebulizer sprays the sample.
  • The solution is carried to the burner, where water is evaporated.
  • Manganese 2+2+ cations are bombarded and converted into ground state atoms.
  • Ground state refers to the stable, happy, state of electrons.
  • Photons from the lamps are tuned to the frequency of the element's outer-shell electrons.
  • Photons collide with electrons, exciting them to a higher energy state.
  • Light absorption is measured, similar to molecular absorption from the previous week.
  • This process is atomic absorption.

Electron Behavior and Light Emission

  • Excited electrons are unstable and drop back to ground state, re-emitting light particles.
  • High concentration solutions and flame heat can excite electrons.
  • As electrons drop back, they emit different colored light.
  • The burner flame is normally blue.
  • Potassium in the flame turns it purple.
  • Copper turns the flame green.
  • Sodium turns the flame orange-yellow.
  • Strontium turns it bright red.
  • Heating the electrons causes them to jump, and the re-emitted light is visible.

Plasma Machines

  • One machine uses a miniature sunny-cycle plasma at 10,000 degrees, using argon.
  • Another machine creates plasma at 5,000 to 6,000 degrees.
  • High temperatures excite every metal's outer shell electrons.
  • As electrons relax, these machines measure the emitted light.

Fireworks and Metal Salts

  • Fireworks utilize these color changes.
  • Different colored fireworks use different metals.
  • Metal salts are used instead of pure metals for safety.
  • Sodium compounds produce bright yellow flames.
  • Copper produces green flames.
  • Strontium produces red flames.
  • Potassium produces weaker pink or purple flames.
  • Calcium and magnesium produce white flames.
  • Nickel can produce blues and greens.

Firework Composition and Function

  • The first charge launches the firework.
  • The second charge explodes, igniting the metals.
  • Electrons jump to a higher energy state, then drop back, emitting light.