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Foods, Flavours and Fragrances Applications 231

(a) 1 4
5 8

7 9
2 3

(b)

1.10 1.20 1.30 1.40 1.50 1.60 1.70 1.80 1.90 2.00 2.10 2.20
Retention time (min)
Figure 10.7 (a) IR reconstructed chromatogram and (b) FID chromatogram of a fraction of
the eucalyptus oil transferred from a DB-Wax column. The secondary separation was carried
out by using an RTX-1701 column, isothermally at 95 °C with a linear velocity of ~90 cm/s.
Peak identification is as follows: (1) water; (2) -pinene; (3) camphene; (4) sabinene; (5) -
pinene; (6) -phellandrene; (7) -terpinene; (8) unknown; (9) -terpinene. Reprinted from
Analytical Chemistry, 66, N. Ragunathan et al., ‘Multidimensional fast gas chromatography
with matrix isolation infrared detection’, pp. 3751–3756, copyright 1994, with permission
from the American Chemical Society.

10.3 MULTIDIMENSIONAL HIGH
PERFORMANCE LIQUID CHROMATOGRAPHY

Multidimensional HPLC offers very high separation power when compared to
monodimensional LC analysis. Thus, it can be applied to the analysis of very com-
plex mixtures. Applications of on-line MD-HPLC have been developed, using vari-
ous techniques such as heart-cut, on-column concentration or trace enrichment;
applications in which liquid phases on both columns are miscible and compatible are
frequently reported, but the on-line coupling of columns with incompatible mobile
phases have also been studied.
The on-line combination of high performance gel filtration chromatography
(GFC), using aqueous compatible, rigid microparticulate exclusion columns, and
reversed-phase chromatography (RPC), using C18 columns, have been employed by
Enri and Frei (32) to separate senna glicoside extracts. This combination is ideal
from the standpoint that the solvents in both techniques are compatible. Another
example of this technique is the analysis of vitamin B in a protein food (33). The
size-exclusion chromatography (SEC) system consisted of a Micropak TSK-2000