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14
CHIRAL SPECIFIC APPLICATIONS OF ESSENTIAL
OILS, FLAVORS, AND PHARMACEUTICALS
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ESSENTIALOILS
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Chiral capillary GC has proven to be a convenient method for characterizing
essential oils anddifferentiating natural flavors from those of synthetic origin.
Chiral compounds from natural origins usually exist as one predominant op-
tical isomer. Also, the inspection of enantiomeric ratios can characterize re-
gional differencesbetweenoils. Although sometimesa result of processing, the
presence of racemic pairs (one-to-one ratios of each enantiomer) most often
indicates adulteration or unnatural origin.
Since most chiral compounds natu-
rallyexistasonepredominant isomer,
resolution ismore challenging, espe-
cially for components in higher con-
centrations.Forprimaryconstituents
in essential oils, select a chiral col-
umn that providesa resolution factor
value greater than two to overcome
possible loss of resolution.
Since essential oils are mixtures of
many compounds, coelutionof peaks
and overlapping of certain optical
pairs are sometimes hard to avoid.
Notall of thechiral compounds found
inanessentialoilor flavorextractmay
separate on the same column. Con-
necting two different columns to-
gether is possible, but the elution or-
der of some enantiomersmay reverse
with this combination, resulting in
loss of separation. Dual column
analysis is a logical alternative to ob-
tain a more complete enantiomeric
profile and to provide confirmational
identification of individual constitu-
ents. To reduce analysis time, both
columns can be installed into the
same injection port for simultaneous
confirmation. (ConsultRestek’sChro-
matographyProductsGuide formore
information about dual column
analysis.)
For primary constituents
in essential oils, select
a chiral column that
provides a resolution
factor value greater than
two to overcome possible
loss of resolution.
