Spectrophotometry

1
Spectrophotometry

• Lecture 13

2
Spectrophotometry

• Terms
• Photon a tiny packet of energy
• Wavelength the distance between two peaks in a
  wave
• absorption refers to the physical process of
  absorbing light
• absorbance refers to the mathematical quantity.
  

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http//en.wikipedia.org/wiki/ImageEM_Spectrum3-ne
w.jpg
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The Ways Colors Exist
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Yellow and Blue Make Green!
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http//www.chm.davidson.edu/ChemistryApplets/spect
rophotometry/Spectrophotometry.html
How a spectrophotometer works
9
The Beer-Lambert Law

• A elc
• A absorbance
• e molar absorptivity
• c concentration (M)
• l distance the light travels through the
  material (usually 1 cm)

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Uses of the Beer-Lambert Law

• Calculating DNA Concentration
• 1.0 Abs260 50 mg/mL ds DNA
• So
• If you have an absorbance of 0.025 then you can
  solve for X to determine the concentration of
  your sample
• 1.0 Abs260 0.025 Abs260
• 50µg/mL X µg/mL

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Activity

• Go learn to use the spectrophotometer and review
  how colors are observed in the lab.