Selection ofColumns for GCxGCAnalysis ofEssential
Oils
Acapillary column coatedwith ahigh-temperature stable wax stationaryphase
for gas chromatography,with a recommended maximumoven temperature of 300
DC,
was installed as part of a comprehensive two-dimensional gas
chromatography
(GCxGC)
column ensemble and the suitability
of this
column
set-up for essential oil analysiswas investigated.The separation of kunzea
essential oil (Kunzea ambigua),which is known for its antibacterial activity, is
used to demonstrate the suitability of the newstationary..
Feb 1, 2010
By:
Robert A. Shellie, PaulD. Morrison, PhilipMariott, Samuel DH. Poynter
LCGC EUROPE
Volume 2, Issue 23,
pp.
76-8'1
Introduction
Multidimensional separations are performed by combining single analytical separation columns in
SUCll away to greatly enhance peak capacity for the separation of complex multi-component
samples . Comprehensive multidimensional gas chromatography (GCxGC) employs largely
independent first- and second-climension separation mechanisms and typically generates peak
capacity of the order of several thousand, making it a highly appropriate technology for the
separation and analysis of complex multicomponent samples such as essential oils.
A substantial majority of GCxGC publications for essential oil analysis in the periodical literature
have used a "non-polar" column in the first dimension and employed a "polar" column in the
second
otrnenslon.'
In practice this almost always translates to use of a 100%
polydimethylsiloxane or 5% diphenyl 95% dimethyl polysiloxane stationary phase in the first–
dimension combined with a 50% diphenyl 50% dimethyl polysiloxane or a polyethylene glycol
(wax) second-dimension column, althouqh there are notable departures from this convention,
including applications reversing the order of "polarity"? providlnq class-type separation of citrus
oil components and those using cyclodextrin derivative stationary phases for enantioselective
analysis
3-8
Even
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polarity, but using an appropriate temperature programme cancels out the influence of volatility
on retention in the second dimension column? ThUS, GCxGC separations are temperature–
programmed to maximize differences in separation mechanisms in the two dimensions.
However, because both columns are commonly lnstallec in the same oven, tne temperature
stability of one of the separation columns tipically imparts an upper temperature limit on the
separation system.Applications that use 50% diphenyl 50% dimethyl polysiloxane second
dimension columns are benefited in terms of rligh-temperature stability comparedWith those
applications employing wax columns, but more suitable selectivity of wax columns for polar
essential oil components was shown many years ago and wax stationary phases are almost
universally
prererred."
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