Page 290 - Multidimensional Chromatography

Biomedical and Pharmaceutical Applications 285

(a) (b) (c)

0.001 a.u.
MMC
0.010 a.u.
0.010 a.u.

0 5 0 5 0 4
Retention time (min) Retention time (min) Retention time (min)
Figure 11.16 Chromatograms of plasma samples obtained by using SPE–SFC with super-
critical desorption of the SPE cartridge: (a) blank plasma (20 l), UV detection at 215 nm; (b)
blank plasma (20 l), UV detection at 360 nm; (c) plasma (1 ml) containing 20 ng mitomycin
C (MMC), UV detection at 360 nm. Reprinted from Journal of Chromatography, 454,W. M.
A. Niessen et al., ‘Phase-system switching as an on-line sample pretreatment in the bioanaly-
sis of mitomycin C using supercritical fluid chromatography,’ pp. 243–251, copyright 1988,
with permission from Elsevier Science.

However, it seems that the presently small attention being given to SFC has also a
negative influence on the interest in SFE, where the latter seems a much more
promising technique.

11.8 COUPLED SYSTEMS INVOLVING
CAPILLARY ELECTROPHORESIS

In the past decade, capillary electrophoresis (CE) has become a widely accepted
tool for the separation of organic and inorganic constituents of complex mixtures.
As is the case for LC, with CE various compound classes can be analysed that are
not amenable to GC. At the same time, the separation efficiency that can be
obtained in CE is much better than in LC. Moreover, CE offers a high speed of
analysis and a very low consumption of chemicals. The various modes of CE are
useful for diverse compounds of biological interest such as drugs, sugars, peptides,
oligonucleotides and proteins. This has revealed the potential for CE in the
biomedical laboratory and, in particular, for the analysis of drugs in body fluids
(153, 154). However, the use of CE in bioanalysis is often precluded by
unfavourable concentration detection limits and by disturbances of the separation
process by matrix compounds. The poor sensitivity is due to the very limited