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Learning Objectives
Apply the principles of chromatography
Explain the chemistry behind the
methods of analysis of compounds
Identify which method is more effective
for the analysis of compounds
Describe the methods used
in the analysis of compounds
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Analysis of Compounds
Dyes
Athletes’ blood / urine
Analysis of
Suspected illegal drugs
Cotton, wool, silk, polyester, nylon?
Unauthorised substances?
Fibres 1
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4
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Analysis of Compounds
Complication
Complex mixtures
A few or one compound(s) of interest
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2
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Analysis of Compounds
Identify the compound
How to separate out mixtures 1
2
Find compound(s) of interest
What is it?
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Chromatography
Separate a mixture into its components
Stationary phase Inert absorbent material
Mobile phase Liquid or gas
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Chromatography
Separate a mixture into its components
Stationary phase Inert absorbent material
Mobile phase Liquid or gas
Longer experiment Greater separation
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Types of Chromatography
Thin Layer Chromatography (TLC) 1
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Thin Layer Chromatography
Blank
plate
Inert
backing
Thin layer of
absorbent
material
TLC plate
under
UV light
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Coloured compounds Inspection
Colourless compounds
UV light
Thin Layer Chromatography
Chemical staining
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Thin Layer Chromatography
Unknown mixture C
Standards A & B
TLC to identify compounds?
Presumptive test
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Thin Layer Chromatography
Too many organic compounds
TLC plate too small
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Thin Layer Chromatography
Unknown spot
corresponding
to standard
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Thin Layer Chromatography
Unknown spot corresponding to standard
Compound is present
Compound may be present
Too many organic compounds
TLC plate too small
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Thin Layer Chromatography
Standards
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Thin Layer Chromatography
Unknown
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Thin Layer Chromatography
Run TLC
Solvent
front
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Thin Layer Chromatography
Run TLC
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Thin Layer Chromatography
Solvent front Compounds present
Green
Black
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2
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Thin Layer Chromatography
Solvent front
Yellow
Red
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4 Unknown
Compounds present
Green
Black
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2
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Thin Layer Chromatography
Retention factor (Rf)
Numerical method to
describe position of spots
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Thin Layer Chromatography
y Solvent front
x1 Rf = x1 / y
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Thin Layer Chromatography
y Solvent front
x1
x2
Rf = x1 / y
Rf = x2 / y
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Thin Layer Chromatography
y Solvent front
x1
x2
x3
Rf = x1 / y
Rf = x3 / y
Rf = x2 / y
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Thin Layer Chromatography
y Solvent front
x1
x2
x3
x4
Rf = x1 / y
Rf = x4 / y
Rf = x3 / y
Rf = x2 / y
