Quant. Anal. Chp 18 Spectromet – Flashcards

1. c= νλ

 2. c/n

• E=h ν = h(c/ λ)

• Smaller Wavelength →Higher Frequency → More Energy
  

Light can be:

• Reflected
• Refracted
• Scattered
• Emitted
• Absorbed

• The fraction of incident light that passes through a sample.
• T = P/P₀

• P₀ is the irradiance (radiant power) striking the sample and P is irradiance emerging from other side of sample.
• P ≤ P₀

• As %: %T = (P/P₀) * 100%

• Most useful quantity for chemical analysis.
• A = log(P₀/P) = -log(T)

A_λ=ε_λbc

• The reason why absorbance is so important is that absorbance is proportional to the concentration of light-absorbing molecules in the sample.

• Works well for dilute solutions (≤ 0.01 M) of most absorbing substances.
• Light must be monochromatic
• Pathlength must be constant (square cuvette) (typically is 1 cm)
• Sample should not:
  • Fluoresce or phosphoresce
  • Scatter light (heterogeneous)
  • Change its chemical composition
    
    
    

• Standard 1-cm path
• Cylindrical
• Microcells