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Lecture 7
Chromatography Intro!
Compounds of interest stick
to sorbent
Solid Phase ExtractionLoad
(sample)
Compounds of interest
released from sorbent
Waste
Eluent(solvent)
Extract
Compounds of interest in a
plug
Chromatography
LoadSample
(injection)
Differential interaction with
stationary phase separates compounds in
time and space.
Detector
Mobile phase
Detector
Mobile phase
ChromatographyDefinition
Separation of components in a mixture based on the differential movement through a porous media under the influence of a mobile phase
First Chromatography Column
toluene
sample
What happens in a chromatographic column?
Gas Chromatography(GC)
Liquid Chromatography(LC)
Distillation Liquid-liquidextraction
Theoretical Plate
Silica support
Stationary phase
GC - gas chromatographyopen tubular columns
Gas (mobile phase)
Theoretical PlateLC - liquid chromatography
packed columns
Silica beads
Stationary phase
liquid (mobile phase)
Number of Theoretical Plates
N = L H
Length of the column
Height equivalent of a theoretical plate
Retention Factor
k’ = tR-tM
tM
= VR-VM
VM
1 < k’ < 10
Describes the strength of the interaction of a compound with the stationary phase
Compounds of interest stick
to sorbent
Solid Phase ExtractionLoad
(sample)
Compounds of interest
released from sorbent
Waste
Eluent(solvent)
Extract
k’ > 1000 k’ < 0.001
Compounds of interest in a
plug
Chromatography
LoadSample
(injection)
Differential interaction with
stationary phase separates compounds in
time and space.
Detector
Mobile phase
Detector
Mobile phase
1 < k’ < 10
Retention Factor (k’)Describes the strength of the interaction of a
compound with the stationary phase
k’ = tR-tM
tM=
VR-VM
VM
1 < k’ < 10
k’ = tR-tM
tM=
VR-VM
VM
1 < k’ < 10
Retention Factor (k’)
Effect of k’ on Selectivity and Resolution in LC
Dong, M. Today’s Chemist at Work. 2000, 9(2), 46-48.
SelectivityDescribes differential mobility of 2 compounds
= k’2
k’1
= K2
K1
ResolutionDescribes how well 2 compounds are separated
Rs = 2(tR2-tR1)
tw1+tw2
ResolutionDescribes how well 2 compounds are separated
Rs = 14
N1/2 (-1)k’
1+k’( )efficiency selectivity
retention