The next generation of hydrolytically stable packing materials:
organic/inorganic hybrids.
Ide, Matthias*(1); Lynen, Frédéric (2); Van Der Voort, Pascal(1)
(1) Department of Inorganic and Physical Chemistry, COMOC, Ghent University.
(2) Department of Organic Chemistry, Separation Science Group, Ghent University.
Krijgslaan 281 (S3(1) & S4bis(2)) B-9000 Ghent, Belgium.
Stationary phase development in HPLC and U(H)PLC has been evolving over the last decades
to the use of ever smaller particles because this allows reduction of the diffusional distances and
a concomitant increase in analytical performance for decreasing separation times. As the
packing of columns with particles of decreasing size affects the columns permeability in a
detrimental way, commercial systems have now been developed operating up to 1300 bar
allowing utilization of these columns at the optimal flow rates and above.
As silica poses significant advantages in terms of rigidity, multi-functionality, surface area and
derivatisation chemistry, it became the golden standard as packing material for HPLC decades
ago. However, because of the raising interest in further increasing inlet pressures and in
exploitation of the benefits of high temperature, purely aqueous or extreme pH LC, the thereby
increasing hydrolytical stability issues of silica need to be addressed in a fundamental way.
To accommodate for these shortcomings, a new type of hybrid silica/carbon stationary phase
was developed based on a cyclic organic/inorganic hybrid precursor. Next to a drastic reduction
in hydrolytically labile groups a major benefit of this material is direct anchoring of the (C18
and other) stationary phase on the cyclic precursor through a highly stable Carbon-carbon bond.
The synthesis of the precursor and of the development of the ensuing entirely new class of
HPLC packing materials is described. The very high pH and temperature stability (>150°C in
purely aqueous HPLC) of the material are demonstrated through a variety of representative
HPLC and UHPLC applications. The application of allyl side-groups and derivatives thereof via
thiol-ene click chemistry are illustrated. Surface area’s > 1000 m2/g with highly narrow pore
size distribution (+/- 3 nm) are also obtained as the material is amendable to mesoporous silica
synthesis strategies.