Supercritical fluid chromatography (SFC) has been gaining
much exposure over recent years. The characteristics inherent
to SFC give it capabilities in separating nonvolatile,
thermally labile compounds inseparable by GC, and with
greater efficiency per unit time than HPLC. As in the past
with the more conventional chromatographic methods, the need
for higher information detectors, such as IR, exists for SFC.
The interface of a Fourier Transform Infrared (FTIR)
spectrometer to a packed column (analytical scale) SFC is
demonstrated. Characterization of mobile phases for SFC-FTIR
is presented. Also, parameters for the optimization of spectral
sensitivity, such as mobile phase transparency and flow
cell design, are discussed. Demonstrations are made via model
mixture separations.
Finally, the application of this technique to the analysis
of free fatty acids is presented. Identification of
carboxylic acids of carbon number 6-18 is made on several
standard mixtures and on free fatty acids extracted from
various complex samples. The spectral identification of the
compounds as free fatty acids is presented, and spectral evidence
for dimerization of the acids in CO 2 and the coelution
of saturated and unsaturated carboxylic acids is shown.
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