Spectrophotometry-III

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Lecture 19

• Spectrophotometry-III

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Monochromator (filter, wavelength selector)
Light Source
Detector
Sample
Spectrometer
Data Processing
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Single beam
Double beam
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A tungsten lamp
3000 K
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UV sources
Deuterium Lamp
Deuterium higher intensity
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Limits to Beers Law
Incident light
Emergent light
P1
P0
Stray light
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Solvents for UV/vis Spectrophotometry
Solvent Lower Wavelength
Limit Water 180 nm Ethanol 220
nm Hexane and 200 nm Cyclohexane Acetone 320
nm
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Bugert, Lambert and Beer
Beers law
A
Straight line!
concentration
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A or ?
Measure _at_ this wavelength!
Other components of the mixture
B
Wavelength, nm
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Limits to Beers Law
Polychromatic light (several wavelength)
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A or ?
Other components of the mixture
Intensity is too low!
B
Wavelength, nm
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A or ?
Other components of the mixture
B
Measurement is difficult
Wavelength, nm
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A or ?
Measure _at_ this wavelength!
Other components of the mixture
C
B reagent ? C
Compound is chemically derivitized (transformed)
prior to the measurement of absorbance
Wavelength, nm
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Cu2
Hg2