Capital HPLC

Cyclobond

Cyclobond

The CSPs are prepared by covalently binding cyclodextrins to silica. Cyclodextrins consist of
glucose units bonded through a-(1,4) linkages forming a truncated cone shaped molecule. They
have a hydrophobic cavity, with polar hydroxyl groups round its edges. The size of the cyclodextrin
hydrophobic cavity, is dependant on the number of glucose units it contains, as outlined below.

Note: Benzene ring diameter = 6.8Å

Resolution is mainly dependant on a tight fit of the solute into the cavity, and on the interactions
between the solute and the secondary hydroxyls, and not on the extent of inclusion. An outer rim of
the hydroxyl groups can be derivatised in a number of ways, eg. acetylated (new phases are becoming
available at the time of writing). These derivatised phases allow chiral interactions to take place,
where previously the solute would have projected well above the edge of the cyclodextrin.
At present there are a few applications on the aand g-cyclodextrin phases. Whereas b-cyclodextrin
phases have a wide range of chiral applications, some of which are listed below:
b-adrenergic blockers, anticonvulsants, anticorticosteriods, antihistamides, antiinflammatories,
amino acid derivatives (dansyl, and b-naphthylesters), barbiturates, CNS simulants, calcium channel
blockers,and diuretics.

Most of these solutes tend to have an aryl and hydrogen bonding groups, near to the chiral centre.
All chiral applications on underivatized cyclodextrins, are in the reverse phase mode, as with non-polar
eluents they behave similarly to diol phases. Mobile phases typically consist of methanol:water, although
buffers like triethylammonium acetate (0.005 to 0.1 M and a pH of 3.0 to 7.0), tend to improve resolution and
peak shape. Replacing methanol with acetonitrile, may also have a similar effect. Dramatic improvements in
resolution can occur in lowering flow rates from 1.0 to 0.5ml/min.
The use of a pre-column packed either with silica or a C18 material is recommended, especially
when using buffered mobile phases. Guard columns are also recommended, especially for
biological applications. These phases are also very useful for preparative separations.

Cyclobond Ordering Information

For prices please see price list page 17-18.

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