Chemistry Reference
In-Depth Information
Integrator or
Computer
Capillary
Detector
+
-
+
Cathode
Anode
Buffer
Buffer
Destination Vial
Source Vial
Sample Vial
High-Voltage
Power Supply
FIGURE 2.4
Capillary zone electrophoresis (CZE) is used to separate ionic species on the
basis of charge, frictional forces, and hydrodynamic radii.
2.10 SIZE- EXCLUSION CHROMATOGRAPHY
In size-exclusion chromatography (SEC), molecules in solution are separated accord-
ing to their size (i.e., molecular weight). This chromatography has been well adapted
to the separation of large molecules, particularly proteins and industrial polymers.
The chromatography is considered a form of gel filtration when an aqueous solution
is used to transport the sample through the column. Gel-permeation chromatography
occurs when an organic solvent is chosen as the mobile phase. A popular gel known
as Sephadex LH20 is widely used to separate small and medium size phenolic com-
pounds. An example of the separation of typical phenolic compounds on Sephadex
LH20 is shown in Figure 2.5.
Conversely, the LH-20 gel can be used as a filtration
method whereby unwanted phenolic compounds can be retained on the gel, allowing
the desired compounds of interest to pass through.
Light-scattering
detector
O
HO
HO
O
OH
OH
O
Absorbance
detector
OH
O
OH
OH
HO
O
OH
Solvent
Pump
Injector
H
Refractive index
detector
OH
Size-exclusion
column
OH
FIGURE 2.5
Typical setup used for size-exclusion (Sephadex LH-20) chromatography for
the separation of phenolic compounds.
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