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Multidimensional Electrodriven Separations 203

Figure 9.4 General schematic illustration of the apparatus used to combine chromatography
with capillary isotachophoresis.

limit, which is comparable to that of polyacrylamide gel electrophoresis. Although
this procedure had the possibility of being completely automated, the run time was
still quite long (13).
Yamamoto et al. also coupled gel permeation HPLC and CE in an on-line fashion
in 1990, where capillary isotachophoresis was again used in the second dimension.
This technique was also not comprehensive due to the loss of resolution between the
techniques. It was also not particularly fast, with a 23 min CE cycle, which was
repeated 90 times throughout the HPLC run (14). Volume incompatibility between
HPLC and CE was one problem not addressed in this study, in which a large HPLC
column was coupled to an electrophoresis capillary.
Other groups have also used LC and CE to perform non-comprehensive multidi-
mensional separations (15, 16). A three-dimensional separation was performed by
Stromqvist in 1994, where size exclusion chromatography (SEC), reverse-phase
HPLC, and CZE were used in an off-line manner to separate peptides (17). The most
useful information gained from all of these non-comprehensive studies was knowl-
edge of the orthogonality and compatibility of LC and CE.

9.6 COMPREHENSIVE TWO-DIMENSIONAL SEPARATIONS
WITH AN ELECTRODRIVEN COMPONENT

The most successful multidimensional electrodriven separations to date have been
performed by James Jorgenson and his group at the University of North Carolina at
Chapel Hill. This group has accomplished several successful comprehensive