Q&A The Column www.thecolumn.eu.com May 2006 Typically these separations
are difficult or impossible to carbon used. It couples an extremely
homogeneous surface achieve with more conventional reversed-phase
materials such with excellent mechanical strength. This means that it is
the as C18 silica gels or polymeric materials. first form of carbon to be
able to take full advantage of PREG illustrates the ability of molecules
having lone-pair or operating conditions as a robust support with near
ideal aromatic-ring electrons to apparently interact with PGC by
properties for HPLC. some kind of electron transfer mechanism to the
electronic PGC can clearly be distinguished in both physical and cloud of
graphitic surface. This is schematically represented by chemical surface
from the more conventional packings such as Figure 2. This interaction is
particularly pronounced when polar bonded silica gels and polymers. The
flat surface coupled with groups are attached to an aromatic ring and
other larger, its 3D graphitic crystalline structure are the key to much
of the aromatic systems. There is now believed to be some type of enhanced
polar retention and stereoselectivity of this phase. orbital overlap
between the conductivity electrons in graphite This is clearly
demonstrated when comparing retention of polar and the lone-pair electrons
in the analytes. species on more conventional columns Figure 3 . How does
this differ from other reverse-phase What sort of analytes is PGC suitable
for? columns? It is suitable for the retention and separation of a wide
range of molecules with particular emphasis of analytes which are PGC is
not the first form of carbon to be used in either insufficiently retained
on conventional reverse-phase chromatography, but it is different from
previous forms of Figure 4: Comparison of Hypercarb with Hypersil
illustrating improved retention. Columns: Hypersil BDS C18 5
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Table of Contents for the Digital Edition of The Column - May 2006