Page 335 - Multidimensional Chromatography

Industrial and Polymer Applications 325

Figure 12.18 LC–SFC analysis of mono- and di-laurates of poly(ethylene glycol) (n
10)
in a surfactant sample: (a) normal phase HPLC trace; (b) chromatogram obtained without
prior fractionation; (c) chromatogram of fraction 1 (F1); (d) chromatogram of fraction 2 (F2).
LC conditions: column (20 cm 0.25 cm i.d.) packed with Shimpak diol; mobile phase,
n-hexane methylene chloride ethanol (75 25 1); flow rate, 4 L min; UV detection at 220
nm. SFC conditions: fused-silica capillary column (15 m 0.1 mm i.d.) with OV-17 (0.25
m film thickness); Pressure-programmed at a rate of 10 atm min from 80 atm to 150 atm,
and then at a rate of 5 atm min; FID detection. Reprinted with permission from Ref. (23).

12.10 SFC–GC APPLICATIONS

An on-line supercritical fluid chromatography–capillary gas chromatography
(SFC–GC) technique has been demonstrated for the direct transfer of SFC frac-
tions from a packed column SFC system to a GC system. This technique has been
applied in the analysis of industrial samples such as aviation fuel (24). This type of
coupled technique is sometimes more advantageous than the traditional LC–GC
coupled technique since SFC is compatible with GC, because most supercritical flu-
ids decompress into gases at GC conditions and are not detected by flame-ioniza-
tion detection. The use of solvent evaporation techniques are not necessary. SFC, in
the same way as LC, can be used to preseparate a sample into classes of compounds
where the individual components can then be analyzed and quantified by GC. The
supercritical fluid sample effluent is decompressed through a restrictor directly into
a capillary GC injection port. In addition, this technique allows selective or multi-
step heart-cutting of various sample peaks as they elute from the supercritical fluid