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SELECTIONGUIDE
RestekCapillaryGCColumnSelectionGuide
Stationary Phase
The stationary phase is the singlemost important considerationwhen you are choosing a
column. The interactions between the analytes and the functional groups of the stationary phase
contributemore to the overall results of the analysis than any other factor.
Table1
summarizes the characteristics, chemical structures and, broadly, suggested uses for
eneral-purpose stationary phases. Change selectivity by choosing a stationary phase
with a different percentage of substitution of a particular functional group (e.g., by switching
from a 5% diphenyl/95% dimethyl polysiloxane stationary phase to a 20% diphenyl/80%
dimethyl polysiloxane stationary phase) or by choosing a stationary phasewith different
functional groups (e.g., by switching from a diphenyl/dimethyl polysiloxane stationary phase to
a polyethylene glycol stationary phase). Note that a stationary phase’s selectivity for sample
components follows the general chemical principle of “like prefers like”: a nonpolar stationary
phase, such as the Rxi®-1methyl polysiloxane stationary phase, will preferentially retain and
separate nonpolar compounds, such as straight-chain hydrocarbons, relative to polar
compounds, such as alcohols. Asmethyl groups are replacedwithmore polar functionalities,
such as phenyl or cyanopropyl groups, selectivity shifts towardmore polar compounds. Polar
phases, such as polyethylene glycol phases (e.g., Stabilwax®), are highly selective toward
alcohols or other polar compounds.
