UV/VIS

 Transmittance T = P/P₀ %T = P/P₀ x 100

 Absorbance A = -log T = log P₀/P

Monochromators

Echelle type grating

nl = d(sin i + sin r )

  concave gratings

focuses and seperates poor resolution

  holographic gratings

Beer's Law

A = ebc

A_total = A₁ + A₂ + A₃ +....

A_total = e₁b₁c₁ + e₂b₂c₂ + e₃b₃c₃ +...

Limitations of Beer's Law

  Real Limitations only works in dilute solutions

High [ ] is > 0.01M

Results

molecular interactions

high electrolyte [ ]

e depends on solution refractive index inc. [ ] = change in ref index

Practical Limitations

Instrumental

UV/VIS Sources

Deuterium Lamp for UV

Tungsten Lamp for VIS

Typical Instrumentation

Single beam

Double beam

Detectors

Photomultiplier tube PMT

Photodiode Array

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Fluorescence, Phosphorescence, and Chemilluminescence

Lasers