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Another example of a
combination is size-exclusion chromatography. SEC bw1 is
often used for (bio)polymers. This separation technique is based on the size of
the analytes. The separation only depends on the stationary phase, unlike other
chromatographic techniques. To be more precise, the separation only occurs in
the pores in the packaging material. This
is typically the reason why SEC columns are tall, allowing for a higher total
pore volume. To improve the separation efficiency, even more, there is the option to put multiple columns in a series. The mobile phase has no influence at all
on the separation efficiency. The stationary phase is often based on porous
silica or on a polymer made out of styrene and divinylbenzene.
The mobile phase consists of an organic
modifier that’s able to dissolve the analyte, most likely THF. 14

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With SEC, it is possible to
obtain information about the molar weight distribution or molar mass averages. The
larger molecules are receiving less retention because they can’t enter the
pores like the smaller molecules can. The larger molecules can only take the
shortest route, passing the pores of the packing material. The smaller
molecules enter every pore on their way,
resulting in a longer route to the end of the column.

The SEC chromatogram is
interpreted a bit different than a
chromatogram from reversed phase chromatography. Every different SEC column has
particle size, the size exclusion limit Vi changes. Large molecules
that have no access to the pores at all
elute between Vi and t0. Because this depends on the

When the analytes have been
the mobile phase, e.g. UV/Vis detector or
concentration, e.g. mass spectrometer. Typically,

 bw1In SEC, analyte molecules ideally do not interact with
hydrodynamic volume will penetrate into smaller pores than larger analyte
larger molecules. SEC is applied for the analysis and characterization of

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