Page 423 - Multidimensional Chromatography

Forensic and Toxicological Applications 415

Figure 15.4 (continued )

with a switching valve or a cryogenically cooled concentrator. The multidimensional
separation may also be combined with on-column or large volume injection.
Applications in forensic and toxicological analysis are presented here, while instru-
mental and theoretical details can be found in Chapters 3 and 4 of this volume.
Recently, multidimensional GC has been employed in enantioselective analysis
by placing a chiral stationary phase such as a cyclodextrin in the second column.
Typically, switching valves are used to heart-cut the appropriate portion of the sepa-
ration from a non-chiral column into a chiral column. Heil et al. used a dual column
system consisting of a non-chiral pre-column (30 m 0.25 mm 0.38 m,
PS-268) and a chiral (30 m 0.32 mm 0.64 m, heptakis(2,3-di-O-methyl-6-O-
tert-butyldimethylsilyl)- -cyclodextrin) (TBDM-CD) analytical column to separate
derivatized urinary organic acids that are indicative of metabolic diseases such as
short bowel syndrome, phenylketonuria, tyrosinaemia, and others. They used a FID
following the pre-column and an ion trap mass-selective detector following the