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Note: All silica-based packings have some solubility in pH >6 aqueous mobile
phases. When using silica-based columns at pH >6, best column lifetime is
obtained at lower temperatures (40 °C Max) using low buffer concentrations in the
range of 0.01 to 0.02 M.
Normal-Phase Column Method Development Notes
The stationary phase is polar in nature and is best used with nonpolar mobile
phases such as methylene chloride/hexane or isopropanol/hexane mixtures.
Increasing the amount of the polar component in these mixtures typically reduces
the retention time of the sample.
Column Type Method Development Notes
ZORBAX NH
2
Polaris NH
2
Many column volumes of mobile phase are necessary
for equilibration to occur after changes in mobile phase
composition. The number of column volumes required
depends on the system in use and can be as high as
50 to 100 column volumes.
ZORBAX Rx-SIL
ZORBAX SIL
Pursuit XRs Si
Polaris Si-A
Microsorb Si
Unbonded silica columns are very sensitive to trace
amounts of water in solvents and sample, so care
must be taken to maintain consistency for method
reproducibility. When gradient elution is employed, both
primary and secondary solvents should be modified
with alcohol or acetonitrile and at least 30 columns of
solvent should be allowed to flow through the column
after completion of each run.
When switching between solvents, first rinse the
column with a mutually miscible solvent such as
isopropyl alcohol.
InfinityLab Poroshell 120
EC-CN
ZORBAX Eclipse XDB-CN
ZORBAX CN
InifintyLab Poroshell 120 EC-CN and ZORBAX Eclipse XDB-
CN columns are shipped with reversed-phase solvents,
but can also be used in normal-phase applications after
flushing with isopropanol.
Retention decreases as the polarity of the mobile phase
increases.
The rapid equilibration of this bonded phase with mobile
phase often makes it more convenient to use this column
than a silica column, especially for gradient elution.
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