Page 139 - Illustrated Pocket Dictionary of Chromatography
P. 139
O
octadecyl-bonded phase, ODS, C18 An octadecyl bonded
phase has a C18 functional group covalently bonded to the surface of
the support material.
R'
Surface Si O Si CH 2 (CH 2 ) 16 CH 3
R
Octadecyl bonded phase
The side groups R and R¢ are commonly methyl groups but can
also be more bulky alkanes (e.g., isopropyl). The identification of these
groups is often omitted in the description of the bonded phase, hence,
octadecyl-bonded phase and not dimethyloctadecyl-bonded phase. In
other instances, the R groups can be reactive functional groups such
as —OH. These groups are used as points from which to make poly-
merized supports or are unmodified to add polarity to the surface.
octanol-water partition coefficient, P o/w Used to estimate
the hydrophobicity of compounds. The importance of this parameter
is that it is an accepted regulatory estimate of the tendency of an
organic compound to bioaccumulate in living cells. Reversed-phase
chromatography has been used as a rapid alternative method for
determining P o/w .
octyl-bonded phase, C8 An octyl bonded phase has a C8 func-
tional group covalently bonded to the surface of the support material.
R'
Surface Si O Si CH 2 (CH 2 ) 6 CH 3
R
Octyl bonded phase
For discussion of the R groups, see octadecyl-bonded phase.
Illustrated Pocket Dictionary of Chromatography, by Paul C. Sadek.
ISBN 0-471-20021-2 Copyright © 2004 John Wiley & Sons, Inc.
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